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      1 #include <cstdio>
      2 
      3 static inline int getPossibleCPUs()
      4 {
      5    FILE* cpuPossible = fopen("/sys/devices/system/cpu/possible", "r");
      6    if(!cpuPossible)
      7        return 1;
      8 
      9    char buf[2000]; //big enough for 1000 CPUs in worst possible configuration
     10    char* pbuf = fgets(buf, sizeof(buf), cpuPossible);
     11    fclose(cpuPossible);
     12    if(!pbuf)
     13       return 1;
     14 
     15    //parse string of form "0-1,3,5-7,10,13-15"
     16    int cpusAvailable = 0;
     17 
     18    while(*pbuf)
     19    {
     20       const char* pos = pbuf;
     21       bool range = false;
     22       while(*pbuf && *pbuf != ',')
     23       {
     24           if(*pbuf == '-') range = true;
     25           ++pbuf;
     26       }
     27       if(*pbuf) *pbuf++ = 0;
     28       if(!range)
     29         ++cpusAvailable;
     30       else
     31       {
     32           int rstart = 0, rend = 0;
     33           sscanf(pos, "%d-%d", &rstart, &rend);
     34           cpusAvailable += rend - rstart + 1;
     35       }
     36 
     37    }
     38    return cpusAvailable ? cpusAvailable : 1;
     39 }
     40 
     41 #define __TBB_HardwareConcurrency() getPossibleCPUs()
     42