//+------------------------------------------------------------------+
//|                                                       Warrior_EA |
//|          CPU thread-pool compute kernels, semantics mirror       |
//|          AI\Network.cl / WarriorDML.cpp exactly (see those files |
//|          for the reference derivation of each kernel).           |
//+------------------------------------------------------------------+
#include "WarriorCPU.h"
#define NOMINMAX
#include <windows.h>
#include <vector>
#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <atomic>
#include <cmath>
#include <algorithm>
#include <future>
#include <chrono>

namespace
{
// Fault isolation boundary: a hardware exception (bad pointer, misaligned
// SIMD access, etc.) or a C++ exception raised while running a kernel must
// never be allowed to unwind past this DLL, because MQL5/#import has no
// concept of an exception - it would fall straight through to the OS
// unhandled-exception path and kill the whole terminal process (this is
// exactly how the 0xc0000409 overnight crash happened). Every kernel
// dispatch and the pool-startup call are routed through these two guards
// instead, so a fault degrades to "this call failed, CPU_GetLastError()
// explains why" - the caller (CNet on the MQL5 side) can retry/reinit
// instead of the whole terminal dying.
//
// Split into their own functions because MSVC forbids mixing __try/__except
// with C++ try/catch in the same function (C2712/C2713) - the C++ exception
// guard and the SEH guard each need their own stack frame.
bool CallFnNoThrow(const std::function<void(int, int)> &fn, int begin, int end)
{
   try
   {
      fn(begin, end);
      return true;
   }
   catch(...)
   {
      return false;
   }
}

bool SehCallFn(const std::function<void(int, int)> &fn, int begin, int end)
{
   __try
   {
      return CallFnNoThrow(fn, begin, end);
   }
   __except(EXCEPTION_EXECUTE_HANDLER)
   {
      return false;
   }
}

bool SehStartPool(class ThreadPool &pool, int threads);

//+------------------------------------------------------------------+
//| Minimal persistent thread pool with a parallel_for helper. Work  |
//| is split into contiguous chunks (one per worker) so cache lines  |
//| stay reasonably local; a countdown latch signals completion.     |
//| Owned exclusively by one CpuContext - never shared across        |
//| contexts, so no cross-instance coordination (grow/refcount) is   |
//| needed here at all, just plain start-once/stop-once lifecycle.   |
//+------------------------------------------------------------------+
class ThreadPool
{
public:
   void Start(int threads)
   {
      Stop();
      if(threads <= 0)
         threads = (int)std::thread::hardware_concurrency();
      if(threads <= 0)
         threads = 1;
      {
         std::lock_guard<std::mutex> lock(m_mutex);
         m_stop = false;
      }
      for(int i = 0; i < threads; i++)
         m_workers.emplace_back([this]{ WorkerLoop(); });
      m_workerCount.store(threads);
   }

   void Stop()
   {
      if(m_workers.empty())
         return;
      {
         std::lock_guard<std::mutex> lock(m_mutex);
         m_stop = true;
      }
      m_cv.notify_all();
      // Bounded wait per worker instead of a plain join(): std::thread has no native timed join, so
      // each worker's join() runs on a throwaway "joiner" thread and this thread waits on it via a
      // future with a timeout instead of blocking directly. CPU_Shutdown() calls Stop() while holding
      // this context's mutex (see its declaration comment) - if MQL5's DLL-call watchdog force-kills
      // the calling thread while it's stuck in an unbounded join(), that mutex would stay locked
      // FOREVER, poisoning every future call against THIS context. Because each context is private to
      // one CDirectMLMy instance (no global/shared state - see CpuContext), that poisoning can no
      // longer take out every other chart's calls into this DLL the way a process-wide singleton
      // would; it only strands the one instance that hit it. Ownership of each worker's std::thread is
      // moved into the joiner's closure, so if we give up and detach the joiner on timeout, the
      // now-empty (moved-from, non-joinable) entry left behind in m_workers is safe to destroy - the
      // joiner keeps running in the background and joins the real worker whenever it actually exits.
      const auto timeout = std::chrono::seconds(10);
      for(auto &t : m_workers)
      {
         if(!t.joinable())
            continue;
         std::promise<void> done;
         std::future<void> fut = done.get_future();
         std::thread joiner([owned = std::move(t), prom = std::move(done)]() mutable
         {
            owned.join();
            prom.set_value();
         });
         if(fut.wait_for(timeout) == std::future_status::timeout)
            joiner.detach();
         else
            joiner.join();
      }
      m_workers.clear();
      m_workerCount.store(0);
      {
         std::lock_guard<std::mutex> lock(m_mutex);
         std::queue<std::function<void()>> empty;
         std::swap(m_tasks, empty);
         m_stop = false;
      }
   }

   int ThreadCount() const { return m_workerCount.load(); }

   ~ThreadPool() { Stop(); }

   // Runs fn(begin,end) once per chunk, chunks covering [0,count) contiguously,
   // one chunk per worker thread; blocks until every chunk has completed.
   // Returns false if any chunk faulted (see SehCallFn) - the caller's buffer
   // is then left partially/not updated by that chunk, so the whole call must
   // be treated as failed rather than silently reporting success.
   //
   // Takes fn BY VALUE and heap-allocates every piece of state the enqueued
   // tasks touch (via shared_ptr), rather than referencing this function's own
   // stack locals. Reason: CpuContext's declaration comment already documents
   // that MQL5's terminal can forcibly kill the DLL-calling thread mid-call if
   // it decides the call is hung. When that happens here, the ThreadPool's
   // worker threads are NOT killed with it - they are independent OS threads
   // that keep running and, previously, kept writing into `remaining`/`allOk`/
   // `doneMutex`/`doneCv` (and calling through `fn`) after the stack frame that
   // owned them had already been torn down. That is a use-after-free into a
   // dead stack - undefined behavior that reliably corrupts the process rather
   // than just failing this one call, which is exactly the class of crash this
   // was supposed to be immune to (see SehCallFn). Every kernel dispatch site
   // below also passes its lambda as [=] rather than [&] for the same reason -
   // a by-reference capture of that call's own local pointers/ints would be
   // just as dangling once its frame is gone.
   bool ParallelFor(int count, std::function<void(int, int)> fn)
   {
      if(count <= 0)
         return true;
      // Below this, the heap allocs + mutex/condvar handoff below cost more than just running the
      // whole range inline on the calling thread - this network's layers are small (tens to low
      // hundreds of neurons), so nearly every dispatch was paying full thread-pool overhead for a
      // sliver of work per thread. Threshold is deliberately conservative (only skips clearly-not-
      // worth-it cases); raise it further if profiling shows larger layers still dominated by overhead.
      const int kInlineThreshold = 512;
      int workers = std::max(1, m_workerCount.load());
      int chunks = std::min(workers, count);
      if(chunks <= 1 || count < kInlineThreshold)
         return SehCallFn(fn, 0, count);

      struct State
      {
         std::atomic<int>        remaining;
         std::atomic<bool>       allOk{true};
         std::mutex              doneMutex;
         std::condition_variable doneCv;
         explicit State(int n) : remaining(n) {}
      };
      auto state = std::make_shared<State>(chunks);
      auto fnPtr = std::make_shared<std::function<void(int, int)>>(std::move(fn));

      int base = count / chunks;
      int extra = count % chunks;
      int start = 0;
      for(int c = 0; c < chunks; c++)
      {
         int len = base + (c < extra ? 1 : 0);
         int begin = start;
         int end = start + len;
         start = end;
         Enqueue([state, fnPtr, begin, end]
         {
            // SehCallFn swallows both hardware faults and C++ exceptions raised
            // inside the kernel; either would otherwise escape this std::thread
            // with no handler and kill the whole terminal process. `remaining`
            // must still be decremented on failure or every other in-flight
            // ParallelFor caller waiting on doneCv would deadlock forever.
            if(!SehCallFn(*fnPtr, begin, end))
               state->allOk.store(false);
            if(state->remaining.fetch_sub(1) == 1)
            {
               std::lock_guard<std::mutex> lock(state->doneMutex);
               state->doneCv.notify_one();
            }
         });
      }

      std::unique_lock<std::mutex> lock(state->doneMutex);
      state->doneCv.wait(lock, [state]{ return state->remaining.load() == 0; });
      return state->allOk.load();
   }

private:
   void Enqueue(std::function<void()> job)
   {
      {
         std::lock_guard<std::mutex> lock(m_mutex);
         m_tasks.push(std::move(job));
      }
      m_cv.notify_one();
   }

   void WorkerLoop()
   {
      for(;;)
      {
         std::function<void()> job;
         {
            std::unique_lock<std::mutex> lock(m_mutex);
            m_cv.wait(lock, [this]{ return m_stop || !m_tasks.empty(); });
            if(m_stop && m_tasks.empty())
               return;
            job = std::move(m_tasks.front());
            m_tasks.pop();
         }
         job();
      }
   }

   std::vector<std::thread>          m_workers;
   std::queue<std::function<void()>> m_tasks;
   std::mutex                        m_mutex;
   std::condition_variable           m_cv;
   bool                              m_stop = false;
   std::atomic<int>                  m_workerCount{0};
};

bool SehStartPool(ThreadPool &pool, int threads)
{
   __try
   {
      pool.Start(threads);
      return true;
   }
   __except(EXCEPTION_EXECUTE_HANDLER)
   {
      return false;
   }
}

struct Buffer
{
   std::vector<double> data;
   bool                inUse = false;
};

//+------------------------------------------------------------------+
//| Everything one CDirectMLMy/CNet instance needs, heap-allocated by |
//| CPU_Init() and handed back as an opaque CpuHandle. No part of     |
//| this DLL keeps any global or static mutable state - every export |
//| below (besides CPU_Init/CPU_GetHardwareConcurrency) operates only |
//| on the CpuContext its caller passes in, so a fault or a wedged    |
//| call (e.g. the mutex-poisoning scenario in ThreadPool::Stop's     |
//| comment) can only ever strand its own context, never another     |
//| instance's, and the DLL can be loaded/used by any number of      |
//| instances or threads in parallel with zero cross-talk.           |
//+------------------------------------------------------------------+
struct CpuContext
{
   // Guards buffers/lastError bookkeeping ONLY - never the parallel dispatch/wait itself. Every
   // kernel below locks this mutex just long enough to validate handles and extract raw buffer
   // pointers, then releases it BEFORE calling pool.ParallelFor(), which blocks (potentially for a
   // while, especially under load) waiting for every worker chunk to finish. MQL5's terminal
   // enforces a hang-watchdog on EA execution: if a #import DLL call ever runs long enough to trip
   // it, the terminal can forcibly terminate the calling thread mid-call. If that termination
   // happened while this thread held `mutex` across a ParallelFor wait, the lock_guard's destructor
   // would never run and `mutex` would stay locked FOREVER - but since it belongs to this context
   // alone, that only poisons future calls against this one instance, not any other chart's.
   std::mutex           mutex;
   ThreadPool           pool;
   int                  lastError = 0;
   std::vector<Buffer>  buffers;
};

int AllocBufferSlot(CpuContext *ctx)
{
   for(size_t i = 0; i < ctx->buffers.size(); i++)
      if(!ctx->buffers[i].inUse)
         return (int)i;
   ctx->buffers.push_back(Buffer());
   return (int)ctx->buffers.size() - 1;
}

bool ValidHandle(CpuContext *ctx, int h)
{
   return h >= 0 && (size_t)h < ctx->buffers.size() && ctx->buffers[h].inUse;
}

inline size_t Size(CpuContext *ctx, int h) { return ctx->buffers[h].data.size(); }
// A caller-supplied count/shape argument mismatched against the actual buffer
// size would index past the end of a std::vector - undefined behavior that
// (unlike an overrun into a GPU UAV buffer) reliably crashes the whole host
// process. Every kernel below validates the exact index range it is about to
// touch against the real buffer sizes first and bails out to an MQL5-visible
// "false" return instead.
#define REQUIRE(ctx, cond) do { if(!(cond)) { (ctx)->lastError = 100; return 0; } } while(0)

// Mirrors AI\Network.cl's MAX_WEIGHT clamp, applied to every weight-update kernel below. Without it a
// gradient spike (e.g. from class-balance oversampling replaying the same rare-class bar several times
// in a row) can drive a weight to +-Infinity; the next Adam step then divides Infinity by Infinity
// (mt/vt both Inf), producing NaN, which propagates through every FeedForward sum that touches it and
// never recovers (Adam(NaN) is always NaN). That silently freezes the whole network at NaN output -
// manifesting as every bar classifying to whatever the "can't decide" default is, since NaN comparisons
// are always false.
// Tightened from 1.0e6 - that ceiling was so loose it never actually engaged before training had
// already gone unstable (real collapses were happening at weight magnitudes several orders of
// magnitude below it). 100.0 matches the equivalent clamp in Dmitriy Gizlyk's reference NeuroNet.mqh
// engine (references\MQL5\Experts\NeuroNet_DNG\NeuroNet.mqh).
const double MAX_WEIGHT = 100.0;
inline double ClampWeight(double w) { return std::max(-MAX_WEIGHT, std::min(MAX_WEIGHT, w)); }

// Floor on the magnitude of a saturated tanh/sigmoid unit's activation derivative. Without this, a
// neuron pinned near its activation extremes (output near -1/0/1) produces a near-zero derivative,
// zeroing that neuron's entire backprop gradient contribution regardless of how wrong its output is -
// it can then never receive a corrective signal to unstick it. 1e-4 matches the equivalent floor in
// Dmitriy Gizlyk's reference NeuroNet.mqh/NeuroNet.cl engine.
const double MIN_ACTIVATION_DERIVATIVE = 1.0e-4;

// Decoupled (AdamW-style) weight decay applied inside every Adam kernel below, on top of the
// MAX_WEIGHT clamp above. MAX_WEIGHT only stops outright +-Infinity/NaN blowups; it does nothing to
// stop weights slowly, unboundedly growing over hundreds of training eras on a fixed, heavily
// class-balance-oversampled dataset (the same rare-class bars replayed up to 5x every single era,
// forever, with no shuffling - see Train()'s reps loop). That slow growth is what was producing the
// multi-hour climb-to-90%+-then-collapse-to-single-digits cycles: OOS accuracy would improve for
// dozens of eras as weights fit the data, then the accumulated growth would push the network into an
// unstable regime (large IS error spike alongside the OOS collapse) before Adam re-settled and the
// climb started over. Every Adam step pulls each weight a small fraction of the way back toward
// zero, capping how large it can drift regardless of how many eras keep pushing it the same
// direction. 0.001, NOT the 0.01 Loshchilov & Hutter default - see AI\Network.mqh's WEIGHT_DECAY
// comment for the full derivation: decay is applied per SAMPLE here (~20k+ online steps/era), and
// 0.01 was observed to grind discriminative weights below the calibration-capped class-prior
// offsets (per-bar logit spread decaying monotonically until argmax degenerated to constant-
// Neutral), while 0.001 still bounds long-run growth. Keep in sync across all four backends.
// UPDATE: weight decay alone did not fully stop the cycles - it targets slow unbounded drift, but the
// actual collapses turned out to be sudden, violent overshoot events (OOS accuracy falling BELOW the
// 33% random-guess floor for 3-class within ~20 eras, IS error spiking to 0.85+ - the model becoming
// confidently wrong, not just uncalibrated). That's a single/few-step Adam blowup, most likely
// triggered by the class-balance oversampling replaying the same rare-class bar up to 5x back-to-back
// every era (see Train()'s reps loop) - 5 identical consecutive gradients build artificially strong,
// correlated momentum (mt) that can overshoot badly once the next, different bar arrives. MAX_WEIGHT_DELTA
// below clips the actual per-step update, not just the resulting weight, which directly bounds how much
// damage any single overshoot step (whatever triggers it) can do.
const double WEIGHT_DECAY = 0.001;
// Per-step update clip - see the UPDATE note above. A healthy Adam step is normally O(lt) (~1e-4 to
// 1e-3 here); 0.1 is generous headroom for legitimate fast learning while hard-stopping the
// multi-order-of-magnitude spikes that were whipping OOS accuracy from 90%+ down to single digits in
// a couple dozen eras. Applied to `delta` BEFORE it's added to the weight, unlike MAX_WEIGHT (which
// only clamps the post-update weight value and is far too loose - 1e6 - to prevent this).
const double MAX_WEIGHT_DELTA = 0.1;
inline double ClampDelta(double d) { return std::max(-MAX_WEIGHT_DELTA, std::min(MAX_WEIGHT_DELTA, d)); }

inline double Activation(double sum, int activation)
{
   if(activation == 0)
      return tanh(sum);
   if(activation == 1)
      return 1.0 / (1.0 + exp(-std::max(-50.0, std::min(50.0, sum))));
   if(activation == 2 && sum < 0)
      return sum * 0.01;
   return sum;
}
} // namespace

//+------------------------------------------------------------------+
//| Lifecycle                                                         |
//+------------------------------------------------------------------+
WARRIORCPU_API CpuHandle __stdcall CPU_Init(int threads)
{
   CpuContext *ctx = new CpuContext();
   if(!SehStartPool(ctx->pool, threads))
   {
      delete ctx; // hardware fault during pool startup - see SehStartPool
      return 0;
   }
   return reinterpret_cast<CpuHandle>(ctx);
}

// Stateless query of the machine's true hardware concurrency - touches no
// context at all, so callers can size a CPU_Init() request correctly without
// a probe-then-discard Init/GetThreadCount/Shutdown roundtrip.
WARRIORCPU_API int __stdcall CPU_GetHardwareConcurrency()
{
   int n = (int)std::thread::hardware_concurrency();
   return n > 0 ? n : 1;
}

WARRIORCPU_API void __stdcall CPU_Shutdown(CpuHandle handle)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return;
   ctx->pool.Stop();
   delete ctx;
}

WARRIORCPU_API int __stdcall CPU_GetLastError(CpuHandle handle)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   std::lock_guard<std::mutex> lock(ctx->mutex);
   return ctx->lastError;
}

WARRIORCPU_API int __stdcall CPU_GetThreadCount(CpuHandle handle)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   return ctx->pool.ThreadCount();
}

//+------------------------------------------------------------------+
//| Buffers                                                           |
//+------------------------------------------------------------------+
WARRIORCPU_API int __stdcall CPU_BufferCreate(CpuHandle handle, int elementCount)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx || elementCount <= 0)
      return -1;
   std::lock_guard<std::mutex> lock(ctx->mutex);
   int slot = AllocBufferSlot(ctx);
   ctx->buffers[slot].data.assign((size_t)elementCount, 0.0);
   ctx->buffers[slot].inUse = true;
   return slot;
}

WARRIORCPU_API void __stdcall CPU_BufferFree(CpuHandle handle, int bufHandle)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return;
   std::lock_guard<std::mutex> lock(ctx->mutex);
   if(bufHandle < 0 || (size_t)bufHandle >= ctx->buffers.size())
      return;
   ctx->buffers[bufHandle] = Buffer();
}

WARRIORCPU_API int __stdcall CPU_BufferWrite(CpuHandle handle, int bufHandle, const double *data, int count)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   std::lock_guard<std::mutex> lock(ctx->mutex);
   if(!ValidHandle(ctx, bufHandle) || (size_t)count > ctx->buffers[bufHandle].data.size())
      return 0;
   // A NaN/Inf slipping into a weight or gradient buffer doesn't crash anything -
   // it silently poisons every value it touches from then on (NaN propagates
   // through every arithmetic op), so training runs for hours producing garbage
   // with no error ever reported. Reject it at the boundary instead.
   for(int i = 0; i < count; i++)
      REQUIRE(ctx, std::isfinite(data[i]));
   std::copy(data, data + count, ctx->buffers[bufHandle].data.begin());
   return 1;
}

WARRIORCPU_API int __stdcall CPU_BufferRead(CpuHandle handle, int bufHandle, double *data, int count)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   std::lock_guard<std::mutex> lock(ctx->mutex);
   if(!ValidHandle(ctx, bufHandle) || (size_t)count > ctx->buffers[bufHandle].data.size())
      return 0;
   std::copy(ctx->buffers[bufHandle].data.begin(), ctx->buffers[bufHandle].data.begin() + count, data);
   return 1;
}

//+------------------------------------------------------------------+
//| Dense feed-forward / gradient / weight-update kernels - mirror   |
//| AI\Network.cl's FeedForward/CaclOutputGradient/CaclHiddenGradient/|
//| UpdateWeightsMomentum/UpdateWeightsAdam 1:1, parallelized over    |
//| the neuron (outer) dimension.                                    |
//+------------------------------------------------------------------+
WARRIORCPU_API int __stdcall CPU_FeedForward(CpuHandle handle, int wHandle, int iHandle, int oHandle, int inputs, int activation)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   int neurons;
   double *w, *in, *out;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, iHandle) || !ValidHandle(ctx, oHandle))
         return 0;
      neurons = (int)Size(ctx, oHandle);
      REQUIRE(ctx, inputs >= 0 && neurons >= 0);
      REQUIRE(ctx, Size(ctx, iHandle) >= (size_t)inputs);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)neurons * (inputs + 1));
      w = ctx->buffers[wHandle].data.data();
      in = ctx->buffers[iHandle].data.data();
      out = ctx->buffers[oHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(neurons, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         int shift = (inputs + 1) * i;
         double sum = 0.0;
         for(int k = 0; k < inputs; k++)
            sum += in[k] * w[shift + k];
         sum += w[shift + inputs];
         out[i] = Activation(sum, activation);
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_CalcOutputGradient(CpuHandle handle, int tHandle, int oHandle, int igHandle, int activation, int count)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *t, *o, *ig;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, tHandle) || !ValidHandle(ctx, oHandle) || !ValidHandle(ctx, igHandle))
         return 0;
      REQUIRE(ctx, count >= 0 && Size(ctx, tHandle) >= (size_t)count && Size(ctx, oHandle) >= (size_t)count && Size(ctx, igHandle) >= (size_t)count);
      t = ctx->buffers[tHandle].data.data();
      o = ctx->buffers[oHandle].data.data();
      ig = ctx->buffers[igHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(count, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         double out_v = o[i];
         double temp = 0.0;
         if(activation == 0)
         {
            // Deliberately NOT multiplied by the tanh derivative (1-out^2):
            // that factor vanishes as out_v approaches +-1, which is exactly
            // where a TANH output neuron needs to converge for a +-1 target
            // (e.g. the buy/sell extremes of a single-neuron regression
            // head), stalling training right when it matters most. Using the
            // raw (target-out) error is the same fix as pairing sigmoid with
            // cross-entropy - the saturating derivative doesn't re-damp the
            // already-correct error signal.
            temp = std::max(-1.0, std::min(1.0, t[i])) - out_v;
         }
         else if(activation == 1)
         {
            // Also deliberately NOT multiplied by the sigmoid derivative out_v*(1-out_v) -
            // same reasoning as activation==0 above. This is the classification output layer
            // (3 neurons, one-hot 0/1 targets); (target-out) unscaled is exactly the
            // sigmoid+binary-cross-entropy gradient (the loss derivative and the sigmoid
            // derivative algebraically cancel), whereas re-multiplying by out_v*(1-out_v) is
            // the MSE-with-sigmoid formula, which damps toward zero as out_v approaches 0 or 1
            // - exactly where a 0/1-target neuron needs to converge. With this damping (plus
            // the 0.00000001 underflow guard at the saturated extremes), the classification
            // output layer's effective learning rate was throttled to a small fraction of the
            // regression path's, observed in practice as all 3 output neurons converging to
            // (and never escaping) an identical value - softmax of three equal logits is
            // always exactly 1/3 each, with ties resolved to index 0 ("Buy" wins by default).
            temp = std::max(0.0, std::min(1.0, t[i])) - out_v;
         }
         else
         {
            // NONE (raw logits - the 3-class softmax classification output layer) and PRELU (2,
            // never actually used as an OUTPUT activation in this codebase) both fall here.
            // Identity/NONE has derivative 1 everywhere, so the plain (target-out) error passes
            // through unscaled - matching CNeuron::calcOutputGradients()'s unconditional formula
            // on the MQL5-side un-accelerated fallback. Leaving this an unhandled else left temp
            // at 0.0, i.e. every softmax-classification output neuron got a permanently zero
            // gradient on this DLL - and since CPU_CalcHiddenGradient propagates backward FROM
            // the output layer's gradient, that silently froze the whole network (not just the
            // output layer) at its random initial weights whenever the CPU tier was active.
            temp = t[i] - out_v;
         }
         ig[i] = temp;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_CalcHiddenGradient(CpuHandle handle, int wHandle, int gHandle, int oHandle, int igHandle,
      int outputs, int activation, int count)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   size_t wSize, oSize, gSize;
   double *w, *g, *o, *ig;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, oHandle) || !ValidHandle(ctx, igHandle))
         return 0;
      REQUIRE(ctx, count >= 0 && outputs >= 0);
      REQUIRE(ctx, Size(ctx, igHandle) >= (size_t)count);
      // count is deliberately Neurons()+1 (an extra row for the bias gradient
      // slot - see Gradient's BufferInit(numNeurons+1,...)), but Output and
      // Weights only have Neurons() rows (no matching bias row), so the last
      // row's index legitimately runs past the end of both buffers. That's a
      // harmless OOB on a GPU UAV read (the result is never used downstream -
      // biases don't get a backprop weight); on CPU every read here is
      // bounds-checked and treated as 0 instead of rejecting the whole call.
      wSize = Size(ctx, wHandle);
      oSize = Size(ctx, oHandle);
      gSize = Size(ctx, gHandle);
      w = ctx->buffers[wHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      o = ctx->buffers[oHandle].data.data();
      ig = ctx->buffers[igHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(count, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         int shift = (outputs + 1) * i;
         double out_v = ((size_t)i < oSize) ? o[i] : 0.0;
         double sum = 0.0;
         for(int k = 0; k < outputs; k++)
         {
            size_t wi = (size_t)shift + k;
            if(wi < wSize && (size_t)k < gSize)
               sum += g[k] * w[wi];
         }
         if(activation == 0)
         {
            sum = std::max(-1.0, std::min(1.0, sum + out_v)) - out_v;
            sum *= std::max(MIN_ACTIVATION_DERIVATIVE, 1.0 - out_v * out_v);
         }
         else if(activation == 1)
         {
            sum = std::max(0.0, std::min(1.0, sum + out_v)) - out_v;
            sum *= std::max(MIN_ACTIVATION_DERIVATIVE, out_v * (1.0 - out_v));
         }
         else if(activation == 2 && out_v < 0.0)
         {
            // PReLU, param=0.01 - unbounded/non-saturating, no clamp/implied-target
            // reformulation needed (matches CPU_CalcHiddenGradientConv's activation==2 branch a
            // few functions below, and AI\Network.cl's CaclHiddenGradient case 2). This branch was
            // missing entirely, so every hidden PReLU layer (the default hidden-layer activation -
            // see ExpertSignalAIBase.mqh's HiddenLayerActivation()) had its backprop gradient left
            // completely unscaled on this backend whenever out_v was negative - a 100x overstated
            // gradient (1.0 instead of the correct 0.01) into that neuron's input weights, active
            // whenever the CPU DLL tier is in use (i.e. no OpenCL GPU available).
            sum *= 0.01;
         }
         ig[i] = sum;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

// Bias weight (j == inputs) is intentionally never touched here, matching
// the OpenCL/DirectML UpdateWeightsMomentum dispatch range (0..inputs-1).
WARRIORCPU_API int __stdcall CPU_UpdateWeightsMomentum(CpuHandle handle, int wHandle, int gHandle, int iHandle, int dwHandle,
      int inputs, double learningRate, double momentum, int neurons)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *w, *g, *in, *dw;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, iHandle) || !ValidHandle(ctx, dwHandle))
         return 0;
      REQUIRE(ctx, neurons >= 0 && inputs >= 0);
      REQUIRE(ctx, Size(ctx, gHandle) >= (size_t)neurons && Size(ctx, iHandle) >= (size_t)inputs);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)neurons * (inputs + 1) && Size(ctx, dwHandle) >= (size_t)neurons * (inputs + 1));
      w = ctx->buffers[wHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      in = ctx->buffers[iHandle].data.data();
      dw = ctx->buffers[dwHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(neurons, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
         for(int j = 0; j < inputs; j++)
         {
            int wi = i * (inputs + 1) + j;
            double delta = learningRate * g[i] * in[j] + momentum * dw[wi];
            dw[wi] = delta;
            w[wi] = ClampWeight(w[wi] + delta);
         }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_UpdateWeightsAdam(CpuHandle handle, int wHandle, int gHandle, int iHandle, int mHandle, int vHandle,
      int inputs, double lt, double b1, double b2, int neurons)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *w, *g, *in, *m, *v;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, iHandle) || !ValidHandle(ctx, mHandle) || !ValidHandle(ctx, vHandle))
         return 0;
      REQUIRE(ctx, neurons >= 0 && inputs >= 0);
      REQUIRE(ctx, Size(ctx, gHandle) >= (size_t)neurons && Size(ctx, iHandle) >= (size_t)inputs);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)neurons * (inputs + 1) && Size(ctx, mHandle) >= (size_t)neurons * (inputs + 1) && Size(ctx, vHandle) >= (size_t)neurons * (inputs + 1));
      w = ctx->buffers[wHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      in = ctx->buffers[iHandle].data.data();
      m = ctx->buffers[mHandle].data.data();
      v = ctx->buffers[vHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(neurons, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
         for(int j = 0; j <= inputs; j++)
         {
            int wi = i * (inputs + 1) + j;
            double inp = (j < inputs) ? in[j] : 1.0;
            double grad = g[i] * inp;
            double mt = b1 * m[wi] + (1.0 - b1) * grad;
            double vt = sqrt(b2 * v[wi] + (1.0 - b2) * grad * grad);
            double delta = ClampDelta(lt * mt / (vt > 0.0 ? vt : lt * 10.0) - lt * WEIGHT_DECAY * w[wi]);
            // No sign-agreement gate (removed 2026-07): gating each step on agreement with the
            // CURRENT sample's gradient sign rectified the one-hot softmax-CCE stream - rare large
            // true-class positives, frequent small wrong-class negatives - into a permanent downward
            // ratchet on every output neuron, sinking all three logits into sigmoid saturation
            // together (the all-Neutral collapse; IS error frozen at sqrt(1/3)=0.58). The stale-step
            // overshoot it guarded against is covered by ClampDelta, AdamW WEIGHT_DECAY and shuffle-
            // interleaved oversampling. Removed from all four backends in sync (AI\NeuronCPU.mqh /
            // WarriorDML.cpp / Network.cl mirror this).
            w[wi] = ClampWeight(w[wi] + delta);
            m[wi] = mt;
            v[wi] = vt;
         }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

//+------------------------------------------------------------------+
//| Convolution kernels - mirror AI\Network.cl's Conv kernels 1:1. A  |
//| single (windowIn+1)*windowOut weight block is shared across every |
//| sliding position.                                                 |
//+------------------------------------------------------------------+
WARRIORCPU_API int __stdcall CPU_FeedForwardConv(CpuHandle handle, int wHandle, int iHandle, int oHandle,
      int inputs, int step, int windowIn, int windowOut, int activation, int positions)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *w, *in, *out;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, iHandle) || !ValidHandle(ctx, oHandle))
         return 0;
      REQUIRE(ctx, positions >= 0 && inputs >= 0 && windowIn >= 0 && windowOut >= 0);
      REQUIRE(ctx, Size(ctx, iHandle) >= (size_t)inputs);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)(windowIn + 1) * windowOut);
      REQUIRE(ctx, Size(ctx, oHandle) >= (size_t)positions * windowOut);
      w = ctx->buffers[wHandle].data.data();
      in = ctx->buffers[iHandle].data.data();
      out = ctx->buffers[oHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(positions, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         int shiftOut = windowOut * i;
         int shiftIn = step * i;
         for(int o = 0; o < windowOut; o++)
         {
            int shift = (windowIn + 1) * o;
            int stop = (windowIn <= (inputs - shiftIn)) ? windowIn : (inputs - shiftIn);
            double sum = 0.0;
            for(int k = 0; k < stop; k++)
               sum += in[shiftIn + k] * w[shift + k];
            sum += w[shift + windowIn];
            out[o + shiftOut] = Activation(sum, activation);
         }
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_CalcHiddenGradientConv(CpuHandle handle, int wHandle, int gHandle, int oHandle, int igHandle,
      int outputs, int step, int windowIn, int windowOut, int activation, int inputCount)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *w, *g, *o, *ig;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, oHandle) || !ValidHandle(ctx, igHandle))
         return 0;
      REQUIRE(ctx, inputCount >= 0 && outputs >= 0 && windowIn >= 0 && windowOut > 0 && step > 0);
      REQUIRE(ctx, Size(ctx, oHandle) >= (size_t)inputCount && Size(ctx, igHandle) >= (size_t)inputCount);
      REQUIRE(ctx, Size(ctx, gHandle) >= (size_t)outputs);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)(windowIn + 1) * windowOut);
      w = ctx->buffers[wHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      o = ctx->buffers[oHandle].data.data();
      ig = ctx->buffers[igHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(inputCount, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         double out_v = o[i];
         int start = i - windowIn + step;
         start = std::max((start - start % step) / step, 0);
         int stop = (i - i % step) / step + 1;
         if(stop > (outputs / windowOut))
            stop = outputs / windowOut;
         double sum = 0.0;
         for(int h = 0; h < windowOut; h++)
            for(int k = start; k < stop; k++)
            {
               int shiftW = (stop - k - 1) * step + i % step + h * (windowIn + 1);
               int shiftG = k * windowOut + h;
               if(shiftG >= outputs || shiftW >= (windowIn + 1) * windowOut)
                  break;
               sum += g[shiftG] * w[shiftW];
            }
         if(activation == 0)
         {
            sum = std::max(-1.0, std::min(1.0, sum + out_v)) - out_v;
            sum *= std::max(MIN_ACTIVATION_DERIVATIVE, 1.0 - out_v * out_v);
         }
         else if(activation == 1)
            sum = (std::max(0.0, std::min(1.0, sum + out_v)) - out_v) * std::max(MIN_ACTIVATION_DERIVATIVE, out_v * (1.0 - out_v));
         else if(activation == 2 && out_v < 0)
            sum *= 0.01;
         ig[i] = sum;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_UpdateWeightsConvMomentum(CpuHandle handle, int wHandle, int gHandle, int iHandle, int dwHandle,
      int inputs, double learningRate, double momentum, int windowIn, int windowOut, int step)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   int total;
   size_t gSize, inSize;
   double *w, *g, *in, *dw;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, iHandle) || !ValidHandle(ctx, dwHandle))
         return 0;
      REQUIRE(ctx, windowIn >= 0 && windowOut >= 0 && step > 0 && inputs >= 0);
      total = (windowIn + 1) * windowOut;
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)total && Size(ctx, dwHandle) >= (size_t)total);
      gSize = Size(ctx, gHandle);
      inSize = Size(ctx, iHandle);
      w = ctx->buffers[wHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      in = ctx->buffers[iHandle].data.data();
      dw = ctx->buffers[dwHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(total, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         int shift = i % (windowIn + 1);
         int shiftOut = (i - shift) / (windowIn + 1);
         int t = (inputs - windowIn) % step;
         t = (inputs - windowIn - t) / step + (t > 0 ? 1 : 0);
         double grad = 0.0;
         for(int k = 0; k < t; k++)
         {
            if(shift != windowIn && (shift + k * step) >= inputs)
               break;
            int gi = k * windowOut + shiftOut;
            int ii = shift + k * step;
            if((size_t)gi >= gSize || (shift != windowIn && (size_t)ii >= inSize))
               break;
            grad += g[gi] * (shift == windowIn ? 1.0 : in[ii]);
         }
         double delta = learningRate * grad + momentum * dw[i];
         dw[i] = delta;
         w[i] = ClampWeight(w[i] + delta);
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_UpdateWeightsConvAdam(CpuHandle handle, int wHandle, int gHandle, int iHandle, int mHandle, int vHandle,
      int inputs, double lt, double b1, double b2, int windowIn, int windowOut, int step)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   int total;
   size_t gSize, inSize;
   double *w, *g, *in, *m, *v;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, iHandle) || !ValidHandle(ctx, mHandle) || !ValidHandle(ctx, vHandle))
         return 0;
      REQUIRE(ctx, windowIn >= 0 && windowOut >= 0 && step > 0 && inputs >= 0);
      total = (windowIn + 1) * windowOut;
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)total && Size(ctx, mHandle) >= (size_t)total && Size(ctx, vHandle) >= (size_t)total);
      gSize = Size(ctx, gHandle);
      inSize = Size(ctx, iHandle);
      w = ctx->buffers[wHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      in = ctx->buffers[iHandle].data.data();
      m = ctx->buffers[mHandle].data.data();
      v = ctx->buffers[vHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(windowIn + 1, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         int t = (inputs - (windowIn - step)) % step;
         t = (inputs - (windowIn - step) - t) / step + (t > 0 ? 1 : 0);
         for(int out = 0; out < windowOut; out++)
         {
            int shiftW = i + out * (windowIn + 1);
            double grad = 0.0;
            for(int k = 0; k < t; k++)
            {
               if(i != windowIn && (i + k * step) >= inputs)
                  break;
               int gi = k * windowOut + out;
               int ii = i + k * step;
               if((size_t)gi >= gSize || (i != windowIn && (size_t)ii >= inSize))
                  break;
               grad += g[gi] * (i == windowIn ? 1.0 : in[ii]);
            }
            double mt = b1 * m[shiftW] + (1.0 - b1) * grad;
            double vt = sqrt(b2 * v[shiftW] + (1.0 - b2) * grad * grad);
            double delta = ClampDelta(lt * mt / (vt > 0.0 ? vt : lt * 10.0) - lt * WEIGHT_DECAY * w[shiftW]);
            // Sign-agreement gate removed - see CPU_UpdateWeightsAdam's comment for why.
            w[shiftW] = ClampWeight(w[shiftW] + delta);
            m[shiftW] = mt;
            v[shiftW] = vt;
         }
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

//+------------------------------------------------------------------+
//| LSTM kernels - mirror AI\Network.cl's LSTM_* kernels 1:1.         |
//+------------------------------------------------------------------+
WARRIORCPU_API int __stdcall CPU_LSTMGates(CpuHandle handle, int wHandle, int hiddenPrevHandle, int inputsHandle,
      int concatenatedHandle, int hiddenSize, int inputSize)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   int perGate;
   double *w, *hp, *in, *cat;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, hiddenPrevHandle) || !ValidHandle(ctx, inputsHandle) || !ValidHandle(ctx, concatenatedHandle))
         return 0;
      REQUIRE(ctx, hiddenSize >= 0 && inputSize >= 0);
      perGate = hiddenSize * (hiddenSize + inputSize + 1);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)4 * perGate);
      REQUIRE(ctx, Size(ctx, hiddenPrevHandle) >= (size_t)hiddenSize && Size(ctx, inputsHandle) >= (size_t)inputSize);
      REQUIRE(ctx, Size(ctx, concatenatedHandle) >= (size_t)4 * hiddenSize);
      w = ctx->buffers[wHandle].data.data();
      hp = ctx->buffers[hiddenPrevHandle].data.data();
      in = ctx->buffers[inputsHandle].data.data();
      cat = ctx->buffers[concatenatedHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(hiddenSize, [=](int begin, int end)
   {
      for(int hid = begin; hid < end; hid++)
         for(int gate = 0; gate < 4; gate++)
         {
            int shift = gate * perGate + hid * (hiddenSize + inputSize + 1);
            double sum = 0.0;
            for(int k = 0; k < hiddenSize; k++)
               sum += hp[k] * w[shift + k];
            for(int k = 0; k < inputSize; k++)
               sum += in[k] * w[shift + hiddenSize + k];
            sum += w[shift + hiddenSize + inputSize];
            double val = (gate < 3) ? (1.0 / (1.0 + exp(-sum))) : tanh(sum);
            cat[gate * hiddenSize + hid] = val;
         }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_LSTMState(CpuHandle handle, int concatenatedHandle, int memoryHandle, int hiddenPrevHandle,
      int hiddenCacheHandle, int outputHandle, int hiddenSize)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *cat, *mem, *hp, *hc, *out;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, concatenatedHandle) || !ValidHandle(ctx, memoryHandle) || !ValidHandle(ctx, hiddenPrevHandle) ||
         !ValidHandle(ctx, hiddenCacheHandle) || !ValidHandle(ctx, outputHandle))
         return 0;
      REQUIRE(ctx, hiddenSize >= 0);
      REQUIRE(ctx, Size(ctx, concatenatedHandle) >= (size_t)4 * hiddenSize);
      REQUIRE(ctx, Size(ctx, memoryHandle) >= (size_t)2 * hiddenSize);
      REQUIRE(ctx, Size(ctx, hiddenPrevHandle) >= (size_t)hiddenSize && Size(ctx, hiddenCacheHandle) >= (size_t)hiddenSize && Size(ctx, outputHandle) >= (size_t)hiddenSize);
      cat = ctx->buffers[concatenatedHandle].data.data();
      mem = ctx->buffers[memoryHandle].data.data();
      hp = ctx->buffers[hiddenPrevHandle].data.data();
      hc = ctx->buffers[hiddenCacheHandle].data.data();
      out = ctx->buffers[outputHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(hiddenSize, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         double f = cat[i];
         double ii = cat[hiddenSize + i];
         double o = cat[2 * hiddenSize + i];
         double gg = cat[3 * hiddenSize + i];
         double c_prev = mem[i];
         mem[hiddenSize + i] = c_prev;
         double c_t = f * c_prev + ii * gg;
         mem[i] = c_t;
         hc[i] = hp[i];
         out[i] = o * tanh(c_t);
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_LSTMGateGradient(CpuHandle handle, int gradientHandle, int memoryHandle, int concatenatedHandle,
      int concatenatedGradientHandle, int hiddenSize)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *grad, *mem, *cat, *cg;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, gradientHandle) || !ValidHandle(ctx, memoryHandle) || !ValidHandle(ctx, concatenatedHandle) || !ValidHandle(ctx, concatenatedGradientHandle))
         return 0;
      REQUIRE(ctx, hiddenSize >= 0);
      REQUIRE(ctx, Size(ctx, gradientHandle) >= (size_t)hiddenSize);
      REQUIRE(ctx, Size(ctx, memoryHandle) >= (size_t)2 * hiddenSize);
      REQUIRE(ctx, Size(ctx, concatenatedHandle) >= (size_t)4 * hiddenSize && Size(ctx, concatenatedGradientHandle) >= (size_t)4 * hiddenSize);
      grad = ctx->buffers[gradientHandle].data.data();
      mem = ctx->buffers[memoryHandle].data.data();
      cat = ctx->buffers[concatenatedHandle].data.data();
      cg = ctx->buffers[concatenatedGradientHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(hiddenSize, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         double c_t = mem[i];
         double c_prev = mem[hiddenSize + i];
         double f = cat[i];
         double ii = cat[hiddenSize + i];
         double o = cat[2 * hiddenSize + i];
         double g = cat[3 * hiddenSize + i];
         double t = tanh(c_t);
         double dh = grad[i];
         // Derivative floor on every gate below - see MIN_ACTIVATION_DERIVATIVE's declaration
         // comment. LSTM gates are sigmoid/tanh by design and routinely sit near their saturated
         // extremes (a fully "open" or "closed" gate), which is exactly where an unfloored
         // derivative goes to zero and blocks gradient from flowing through the recurrent path at
         // all.
         double dc = dh * o * std::max(MIN_ACTIVATION_DERIVATIVE, 1.0 - t * t);
         cg[2 * hiddenSize + i] = dh * t * std::max(MIN_ACTIVATION_DERIVATIVE, o * (1.0 - o));
         cg[i] = dc * c_prev * std::max(MIN_ACTIVATION_DERIVATIVE, f * (1.0 - f));
         cg[hiddenSize + i] = dc * g * std::max(MIN_ACTIVATION_DERIVATIVE, ii * (1.0 - ii));
         cg[3 * hiddenSize + i] = dc * ii * std::max(MIN_ACTIVATION_DERIVATIVE, 1.0 - g * g);
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_LSTMWeightsGradient(CpuHandle handle, int concatenatedGradientHandle, int hiddenCacheHandle,
      int inputsHandle, int weightsGradientHandle, int hiddenSize, int inputSize)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   int perGate, total;
   double *cg, *hc, *in, *wg;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, concatenatedGradientHandle) || !ValidHandle(ctx, hiddenCacheHandle) || !ValidHandle(ctx, inputsHandle) || !ValidHandle(ctx, weightsGradientHandle))
         return 0;
      REQUIRE(ctx, hiddenSize >= 0 && inputSize >= 0);
      perGate = hiddenSize * (hiddenSize + inputSize + 1);
      total = 4 * perGate;
      REQUIRE(ctx, Size(ctx, concatenatedGradientHandle) >= (size_t)4 * hiddenSize);
      REQUIRE(ctx, Size(ctx, hiddenCacheHandle) >= (size_t)hiddenSize && Size(ctx, inputsHandle) >= (size_t)inputSize);
      REQUIRE(ctx, Size(ctx, weightsGradientHandle) >= (size_t)total);
      cg = ctx->buffers[concatenatedGradientHandle].data.data();
      hc = ctx->buffers[hiddenCacheHandle].data.data();
      in = ctx->buffers[inputsHandle].data.data();
      wg = ctx->buffers[weightsGradientHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(total, [=](int begin, int end)
   {
      for(int wi = begin; wi < end; wi++)
      {
         int gate = wi / perGate;
         int rem = wi % perGate;
         int hid = rem / (hiddenSize + inputSize + 1);
         int k = rem % (hiddenSize + inputSize + 1);
         double inp = (k < hiddenSize) ? hc[k] : ((k < hiddenSize + inputSize) ? in[k - hiddenSize] : 1.0);
         wg[wi] = cg[gate * hiddenSize + hid] * inp;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_LSTMInputsGradient(CpuHandle handle, int concatenatedGradientHandle, int wHandle,
      int inputsGradientHandle, int hiddenSize, int inputSize)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   int perGate;
   double *cg, *w, *ig;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, concatenatedGradientHandle) || !ValidHandle(ctx, wHandle) || !ValidHandle(ctx, inputsGradientHandle))
         return 0;
      REQUIRE(ctx, hiddenSize >= 0 && inputSize >= 0);
      perGate = hiddenSize * (hiddenSize + inputSize + 1);
      REQUIRE(ctx, Size(ctx, concatenatedGradientHandle) >= (size_t)4 * hiddenSize);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)4 * perGate);
      REQUIRE(ctx, Size(ctx, inputsGradientHandle) >= (size_t)inputSize);
      cg = ctx->buffers[concatenatedGradientHandle].data.data();
      w = ctx->buffers[wHandle].data.data();
      ig = ctx->buffers[inputsGradientHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(inputSize, [=](int begin, int end)
   {
      for(int j = begin; j < end; j++)
      {
         double sum = 0.0;
         for(int gate = 0; gate < 4; gate++)
            for(int hid = 0; hid < hiddenSize; hid++)
               sum += cg[gate * hiddenSize + hid] * w[gate * perGate + hid * (hiddenSize + inputSize + 1) + hiddenSize + j];
         ig[j] = sum;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_LSTMUpdateWeightsAdam(CpuHandle handle, int wHandle, int weightsGradientHandle,
      int mHandle, int vHandle, double l, double b1, double b2, int total)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *w, *wg, *m, *v;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, weightsGradientHandle) || !ValidHandle(ctx, mHandle) || !ValidHandle(ctx, vHandle))
         return 0;
      REQUIRE(ctx, total >= 0);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)total && Size(ctx, weightsGradientHandle) >= (size_t)total);
      REQUIRE(ctx, Size(ctx, mHandle) >= (size_t)total && Size(ctx, vHandle) >= (size_t)total);
      w = ctx->buffers[wHandle].data.data();
      wg = ctx->buffers[weightsGradientHandle].data.data();
      m = ctx->buffers[mHandle].data.data();
      v = ctx->buffers[vHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(total, [=](int begin, int end)
   {
      for(int wi = begin; wi < end; wi++)
      {
         double g = wg[wi];
         double mt = b1 * m[wi] + (1.0 - b1) * g;
         double vt = sqrt(b2 * v[wi] + (1.0 - b2) * g * g);
         double delta = ClampDelta(l * mt / (vt > 0.0 ? vt : l * 10.0) - l * WEIGHT_DECAY * w[wi]);
         // Sign-agreement gate removed - see CPU_UpdateWeightsAdam's comment for why.
         w[wi] = ClampWeight(w[wi] + delta);
         m[wi] = mt;
         v[wi] = vt;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

// SGD+momentum counterpart to CPU_LSTMUpdateWeightsAdam - same flat
// (already-elementwise) weights_gradient/DeltaWeightsLSTM layout, just the
// classic heavy-ball update instead of Adam's per-parameter adaptive step.
// See CPU_UpdateWeightsMomentum's matching comment for why the dense-layer
// version doesn't need this treatment: this is the LSTM path's counterpart,
// so it always uses the flat total-weight indexing already established by
// CPU_LSTMUpdateWeightsAdam above.
WARRIORCPU_API int __stdcall CPU_LSTMUpdateWeightsMomentum(CpuHandle handle, int wHandle, int weightsGradientHandle,
      int dwHandle, double learningRate, double momentum, int total)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *w, *wg, *dw;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, wHandle) || !ValidHandle(ctx, weightsGradientHandle) || !ValidHandle(ctx, dwHandle))
         return 0;
      REQUIRE(ctx, total >= 0);
      REQUIRE(ctx, Size(ctx, wHandle) >= (size_t)total && Size(ctx, weightsGradientHandle) >= (size_t)total);
      REQUIRE(ctx, Size(ctx, dwHandle) >= (size_t)total);
      w = ctx->buffers[wHandle].data.data();
      wg = ctx->buffers[weightsGradientHandle].data.data();
      dw = ctx->buffers[dwHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(total, [=](int begin, int end)
   {
      for(int wi = begin; wi < end; wi++)
      {
         double delta = learningRate * wg[wi] + momentum * dw[wi];
         dw[wi] = delta;
         w[wi] = ClampWeight(w[wi] + delta);
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

//+------------------------------------------------------------------+
//| Max-pooling layer - no weights, mirrors AI\Network.cl's           |
//| FeedForwardProof/CalcInputGradientProof.                          |
//+------------------------------------------------------------------+
WARRIORCPU_API int __stdcall CPU_FeedForwardProof(CpuHandle handle, int iHandle, int oHandle, int inputs, int window, int step, int outputs)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   size_t inSize;
   double *in, *out;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, iHandle) || !ValidHandle(ctx, oHandle))
         return 0;
      REQUIRE(ctx, outputs >= 0 && inputs >= 0 && step > 0);
      REQUIRE(ctx, Size(ctx, iHandle) >= (size_t)inputs && Size(ctx, oHandle) >= (size_t)outputs);
      inSize = Size(ctx, iHandle);
      in = ctx->buffers[iHandle].data.data();
      out = ctx->buffers[oHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(outputs, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         int pos = i * step;
         if((size_t)pos >= inSize)
         {
            out[i] = 0.0;
            continue;
         }
         double result = in[pos];
         for(int k = 1; k < window; k++)
         {
            int shift = k + pos;
            if(shift >= inputs || (size_t)shift >= inSize)
               break;
            result = std::max(result, in[shift]);
         }
         out[i] = result;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}

WARRIORCPU_API int __stdcall CPU_CalcInputGradientProof(CpuHandle handle, int iHandle, int gHandle, int oHandle, int igHandle,
      int outputs, int window, int step, int inputs)
{
   CpuContext *ctx = reinterpret_cast<CpuContext*>(handle);
   if(!ctx)
      return 0;
   double *in, *g, *o, *ig;
   {
      // see CpuContext's declaration comment - lock scope stops here, before the blocking ParallelFor
      std::lock_guard<std::mutex> lock(ctx->mutex);
      if(!ValidHandle(ctx, iHandle) || !ValidHandle(ctx, gHandle) || !ValidHandle(ctx, oHandle) || !ValidHandle(ctx, igHandle))
         return 0;
      REQUIRE(ctx, inputs >= 0 && outputs >= 0 && step > 0);
      REQUIRE(ctx, Size(ctx, iHandle) >= (size_t)inputs && Size(ctx, igHandle) >= (size_t)inputs);
      REQUIRE(ctx, Size(ctx, oHandle) >= (size_t)outputs && Size(ctx, gHandle) >= (size_t)outputs);
      in = ctx->buffers[iHandle].data.data();
      g = ctx->buffers[gHandle].data.data();
      o = ctx->buffers[oHandle].data.data();
      ig = ctx->buffers[igHandle].data.data();
   }
   if(!ctx->pool.ParallelFor(inputs, [=](int begin, int end)
   {
      for(int i = begin; i < end; i++)
      {
         double value = in[i];
         int start = i - window + step;
         start = (start - start % step) / step;
         int stop = (i - i % step) / step + 1;
         double prevGrad = 0.0;
         for(int out = std::max(0, start); out < std::min(outputs, stop); out++)
            if(value == o[out])
               prevGrad += g[out];
         ig[i] = prevGrad;
      }
   }))
   {
      ctx->lastError = 201;
      return 0;
   }
   return 1;
}