forked from rosh/MQL5Book
130 lines
5.1 KiB
MQL5
130 lines
5.1 KiB
MQL5
//+------------------------------------------------------------------+
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//| GlobalsWithCondition.mq5 |
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//| Copyright 2021, MetaQuotes Ltd. |
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//| https://www.mql5.com |
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//+------------------------------------------------------------------+
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#property service
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#include "..\..\Include\PRTF.mqh"
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// maximal number of concurrently running copies of the program
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input int limit = 1; // Limit
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input int startPause = 100; // Delay (ms)
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//+------------------------------------------------------------------+
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//| Delay emulation |
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//+------------------------------------------------------------------+
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void Delay()
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{
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if(startPause > 0)
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{
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Sleep(startPause);
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}
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}
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//+------------------------------------------------------------------+
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//| Service program start function |
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//+------------------------------------------------------------------+
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void OnStart()
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{
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PrintFormat("\nParameters: Limit: %d, Delay: %d", limit, startPause);
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// create new temporary variable if it's not exist
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// keep current value otherwise
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PRTF(GlobalVariableTemp(__FILE__));
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// precondition guards
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int count = (int)GlobalVariableGet(__FILE__);
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if(count < 0)
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{
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Print("Negative count detected. Not allowed.");
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return;
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}
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if(count >= limit)
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{
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PrintFormat("Can't start more than %d copy(s)", limit);
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return;
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}
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const int maxRetries = 5;
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int retry = 0;
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while(count < limit && retry < maxRetries)
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{
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// emulate slow execution in busy conditions,
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// where multiple programs run in parallel
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Delay();
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if(PRTF(GlobalVariableSetOnCondition(__FILE__, count + 1, count))) break;
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// conditional assignment failed, try again with updated base value
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count = (int)GlobalVariableGet(__FILE__);
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PrintFormat("Counter is already altered by other instance: %d", count);
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retry++;
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}
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if(count == limit || retry == maxRetries)
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{
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PrintFormat("Start failed: count: %d, retries: %d", count, retry);
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return;
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}
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// work cycle (mockup)
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int loop = 0;
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while(!IsStopped())
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{
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PrintFormat("Copy %d is working [%d]...", count, loop++);
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// ...
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Sleep(3000);
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}
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retry = 0;
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int last = (int)GlobalVariableGet(__FILE__);
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while(last > 0 && retry < maxRetries)
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{
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PrintFormat("Copy %d (out of %d) is stopping", count, last);
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Delay();
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if(PRTF(GlobalVariableSetOnCondition(__FILE__, last - 1, last))) break;
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last = (int)GlobalVariableGet(__FILE__);
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retry++;
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}
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if(last <= 0)
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{
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PrintFormat("Unexpected exit: %d", last);
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}
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else
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{
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PrintFormat("Stopped copy %d: count: %d, retries: %d", count, last, retry);
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}
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}
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//+------------------------------------------------------------------+
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/*
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example output
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GlobalsWithCondition 2 GlobalVariableTemp(GlobalsWithCondition.mq5)=false / GLOBALVARIABLE_EXISTS(4502)
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GlobalsWithCondition 1 GlobalVariableTemp(GlobalsWithCondition.mq5)=false / GLOBALVARIABLE_EXISTS(4502)
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GlobalsWithCondition GlobalVariableTemp(GlobalsWithCondition.mq5)=true / ok
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GlobalsWithCondition GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,count+1,count)=true / ok
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GlobalsWithCondition 1 GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,count+1,count)=false / GLOBALVARIABLE_NOT_FOUND(4501)
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GlobalsWithCondition 2 GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,count+1,count)=false / GLOBALVARIABLE_NOT_FOUND(4501)
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GlobalsWithCondition 1 Counter is already altered by other instance: 1
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GlobalsWithCondition Copy 0 is working [0]...
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GlobalsWithCondition 2 Counter is already altered by other instance: 1
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GlobalsWithCondition 1 GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,count+1,count)=true / ok
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GlobalsWithCondition 1 Copy 1 is working [0]...
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GlobalsWithCondition 2 GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,count+1,count)=false / GLOBALVARIABLE_NOT_FOUND(4501)
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GlobalsWithCondition 2 Counter is already altered by other instance: 2
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GlobalsWithCondition 2 Start failed: count: 2, retries: 2
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GlobalsWithCondition Copy 0 is working [1]...
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GlobalsWithCondition 1 Copy 1 is working [1]...
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GlobalsWithCondition Copy 0 is working [2]...
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GlobalsWithCondition 1 Copy 1 is working [2]...
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GlobalsWithCondition Copy 0 is working [3]...
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GlobalsWithCondition 1 Copy 1 is working [3]...
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GlobalsWithCondition Copy 0 (out of 2) is stopping
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GlobalsWithCondition GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,last-1,last)=true / ok
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GlobalsWithCondition Stopped copy 0: count: 2, retries: 0
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GlobalsWithCondition 1 Copy 1 (out of 1) is stopping
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GlobalsWithCondition 1 GlobalVariableSetOnCondition(GlobalsWithCondition.mq5,last-1,last)=true / ok
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GlobalsWithCondition 1 Stopped copy 1: count: 1, retries: 0
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*/
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//+------------------------------------------------------------------+
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