其实只要

#include <unistd.h>
long num = sysconf(_SC_NPROCESSORS_ONLN);

便可以获得当前CPU的数量。。。

判断依据：
1.具有相同core id的cpu是同一个core的超线程。
2.具有相同physical id的cpu是同一颗cpu封装的线程或者cores。

英文版：
1.Physical id and core id are not necessarily consecutive but they are unique. Any cpu with the same core id are hyperthreads in the same core.
2.Any cpu with the same physical id are threads or cores in the same p