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GRID: avoid integer overflow (#3927)

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- On higher core-count systems, the adjusted expressions can overflow.
- For example (16 ranks, 384 threads), the lower bound was negative.
- Avoid subsequent OOB access.
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Hans Pabst 2025-02-02 10:59:21 +01:00 • committed by GitHub
parent aac52debd2
commit b7bcddc135
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1 changed files with 7 additions and 6 deletions
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13
src/grid/cpu/grid_cpu_task_list.c
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@ -379,10 +379,11 @@ static void collocate_one_grid_level(
const int actual_group_size = imin(group_size, nthreads - dest_thread);
// Parallelize summation by dividing grid points across group members.
const int rank = modulo(ithread, group_size); // position within the group
const int lb = (npts_local_total * rank) / actual_group_size;
const int ub = (npts_local_total * (rank + 1)) / actual_group_size;
const int64_t lb = ((int64_t)npts_local_total * rank) / actual_group_size;
const int64_t ub =
((int64_t)npts_local_total * (rank + 1)) / actual_group_size;
if (src_thread < nthreads) {
for (int i = lb; i < ub; i++) {
for (int i = (int)lb; i < (int)ub; i++) {
task_list->threadlocals[dest_thread][i] +=
task_list->threadlocals[src_thread][i];
}
@ -391,9 +392,9 @@ static void collocate_one_grid_level(
}
// Copy final result from first thread into shared grid.
const int lb = (npts_local_total * ithread) / nthreads;
const int ub = (npts_local_total * (ithread + 1)) / nthreads;
for (int i = lb; i < ub; i++) {
const int64_t lb = ((int64_t)npts_local_total * ithread) / nthreads;
const int64_t ub = ((int64_t)npts_local_total * (ithread + 1)) / nthreads;
for (int i = (int)lb; i < (int)ub; i++) {
grid->host_buffer[i] = task_list->threadlocals[0][i];
}