if (nproc == 0) {
#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
nproc = sysconf(_SC_NPROCESSORS_ONLN);
#elif defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_CONF)
nproc = sysconf(_SC_NPROCESSORS_CONF);
if (nproc == 0) {
#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
nproc = sysconf(_SC_NPROCESSORS_ONLN);
#elif defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_CONF)
nproc = sysconf(_SC_NPROCESSORS_CONF);