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Replace a bit counting loop with an efficient population count #1297

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Merged
merged 1 commit into from
Jan 13, 2016
Merged

Replace a bit counting loop with an efficient population count #1297

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12 changes: 3 additions & 9 deletions opal/mca/hwloc/base/hwloc_base_util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -579,16 +579,10 @@ unsigned int opal_hwloc_base_get_npus(hwloc_topology_t topo,
* one bit for each available pu. We could just
* subtract the first and last indices, but there
* may be "holes" in the bitmap corresponding to
* offline or unallowed cpus - so we have to
* search for them
* offline or unallowed cpus - so we count them with
* the bitmap "weight" (a.k.a. population count) function
*/
for (i=hwloc_bitmap_first(cpuset), cnt=0;
i <= hwloc_bitmap_last(cpuset);
i++) {
if (hwloc_bitmap_isset(cpuset, i)) {
cnt++;
}
}
cnt = hwloc_bitmap_weight(cpuset);
}
/* cache the info */
data = (opal_hwloc_obj_data_t*)obj->userdata; // in case it was added
Expand Down