#include <cstdio>

static inline int getPossibleCPUs()
{
   FILE* cpuPossible = fopen("/sys/devices/system/cpu/possible", "r");
   if(!cpuPossible)
       return 1;

   char buf[2000]; //big enough for 1000 CPUs in worst possible configuration
   char* pbuf = fgets(buf, sizeof(buf), cpuPossible);
   fclose(cpuPossible);
   if(!pbuf)
      return 1;

   //parse string of form "0-1,3,5-7,10,13-15"
   int cpusAvailable = 0;

   while(*pbuf)
   {
      const char* pos = pbuf;
      bool range = false;
      while(*pbuf && *pbuf != ',')
      {
          if(*pbuf == '-') range = true;
          ++pbuf;
      }
      if(*pbuf) *pbuf++ = 0;
      if(!range)
        ++cpusAvailable;
      else
      {
          int rstart = 0, rend = 0;
          sscanf(pos, "%d-%d", &rstart, &rend);
          cpusAvailable += rend - rstart + 1;
      }

   }
   return cpusAvailable ? cpusAvailable : 1;
}

#define __TBB_HardwareConcurrency() getPossibleCPUs()