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POCan a value in std::map for a key be locked?
 

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  1. POCan a value in std::map for a key be locked?
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    <p>I have a simple std::map having key-value. I want this map to be thread safe. I do not want to lock the entire map. Since my threads would be working(update,delete) only on the values for a particular key in the map, I do not wish to lock the entire map. I want the other threads to be able to work on the map, of course not on the locked value. </p> <p>Would it be advisable or logically correct to lock only the value for a specific key? OR I should think of another data structure?</p> <p>Update: I just tried a sample example where i have parallel threads updating and inserting in the same map . </p> <pre><code>#include "stdafx.h" #include "stdafx.h" #include &lt;iostream&gt; #include &lt;map&gt; #include &lt;process.h&gt; #include &lt;windows.h&gt; using namespace std; CRITICAL_SECTION CriticalSection; struct newEntry { int key; char value; }; std::map&lt;int,char&gt; mapIntChar; unsigned __stdcall UpdateThreadFunc( void* pArguments ) { char *ptr = (char *) pArguments; EnterCriticalSection(&amp;CriticalSection); *ptr = 'Z'; LeaveCriticalSection(&amp;CriticalSection); _endthreadex( 0 ); return 0; } unsigned __stdcall InsertThreadFunc( void* pArguments ) { struct newEntry *ptr = (struct newEntry *) pArguments; mapIntChar[ptr-&gt;key] = ptr-&gt;value; _endthreadex( 0 ); return 0; } int _tmain(int argc, _TCHAR* argv[]) { std::map&lt;int,char&gt;::iterator it1; unsigned threadID; if (!InitializeCriticalSectionAndSpinCount(&amp;CriticalSection, 0x00000400) ) return 0; mapIntChar[0] = 'A'; mapIntChar[1] = 'B'; mapIntChar[2] = 'C'; mapIntChar[3] = 'D'; HANDLE hThread; int nCount = 0; struct newEntry *newIns; while ( nCount &lt; 1004) { it1 = mapIntChar.begin(); char *ptr = &amp;(it1-&gt;second); hThread = (HANDLE)_beginthreadex( NULL, 0, &amp;UpdateThreadFunc, ptr, 0, &amp;threadID ); newIns = new newEntry; newIns-&gt;key = rand() % 1000; newIns-&gt;value = 'K'; hThread = (HANDLE)_beginthreadex( NULL, 0, &amp;InsertThreadFunc, newIns, 0, &amp;threadID ); nCount++; delete newIns; } } </code></pre>
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    1. USsameer karjatkar
    1. USsameer karjatkar
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      1. VTUpMod
    1. COBy the way, putting spaces *before* sentence signs is bad practice. Just so you know for future machine writings.
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      1. USChristian Rau
    2. CO@ChristianRau I'll take care
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      1. USsameer karjatkar
 

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