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coll: make bcast ring unsigned-safe #13287

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Merged
merged 1 commit into from
Jun 10, 2025
Merged

coll: make bcast ring unsigned-safe #13287

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1 change: 1 addition & 0 deletions config/opal_setup_cc.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -277,6 +277,7 @@ AC_DEFUN([OPAL_SETUP_CC],[
_OPAL_CHECK_SPECIFIC_CFLAGS(-Wstrict-prototypes, Wstrict_prototypes)
_OPAL_CHECK_SPECIFIC_CFLAGS(-Wcomment, Wcomment)
_OPAL_CHECK_SPECIFIC_CFLAGS(-Wshadow, Wshadow)
_OPAL_CHECK_SPECIFIC_CFLAGS(-Wtype-limits,Wtype_limits)
_OPAL_CHECK_SPECIFIC_CFLAGS(-Werror-implicit-function-declaration, Werror_implicit_function_declaration)
_OPAL_CHECK_SPECIFIC_CFLAGS(-Wno-long-double, Wno_long_double, int main() { long double x; })
_OPAL_CHECK_SPECIFIC_CFLAGS(-fno-strict-aliasing, fno_strict_aliasing, int main() { long double x; })
Expand Down
78 changes: 46 additions & 32 deletions ompi/mca/coll/base/coll_base_bcast.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
* Copyright (c) 2016 Research Organization for Information Science
* and Technology (RIST). All rights reserved.
* Copyright (c) 2017 IBM Corporation. All rights reserved.
* Copyright (c) 2025 Triad National Security, LLC. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
Expand All @@ -34,6 +35,15 @@
#include "coll_base_topo.h"
#include "coll_base_util.h"

/*
* if a > b return a- b otherwise 0
*/
static inline size_t
rectify_diff(size_t a, size_t b)
{
return a > b ? a - b : 0;
}

int
ompi_coll_base_bcast_intra_generic( void* buffer,
size_t original_count,
Expand Down Expand Up @@ -811,8 +821,8 @@ int ompi_coll_base_bcast_intra_scatter_allgather(
if (vrank & mask) {
int parent = (rank - mask + comm_size) % comm_size;
/* Compute an upper bound on recv block size */
recv_count = count - vrank * scatter_count;
if (recv_count <= 0) {
recv_count = rectify_diff(count, (size_t)(vrank * scatter_count));
if (recv_count == 0) {
curr_count = 0;
} else {
/* Recv data from parent */
Expand All @@ -832,7 +842,7 @@ int ompi_coll_base_bcast_intra_scatter_allgather(
mask >>= 1;
while (mask > 0) {
if (vrank + mask < comm_size) {
send_count = curr_count - scatter_count * mask;
send_count = rectify_diff(curr_count, (size_t)(scatter_count * mask));
if (send_count > 0) {
int child = (rank + mask) % comm_size;
err = MCA_PML_CALL(send((char *)buf + (ptrdiff_t)scatter_count * (vrank + mask) * extent,
Expand All @@ -850,10 +860,8 @@ int ompi_coll_base_bcast_intra_scatter_allgather(
* Allgather by recursive doubling
* Each process has the curr_count elems in the buf[vrank * scatter_count, ...]
*/
size_t rem_count = count - vrank * scatter_count;
size_t rem_count = rectify_diff(count, (size_t)(vrank * scatter_count));
curr_count = (scatter_count < rem_count) ? scatter_count : rem_count;
if (curr_count < 0)
curr_count = 0;

mask = 0x1;
while (mask < comm_size) {
Expand All @@ -866,9 +874,7 @@ int ompi_coll_base_bcast_intra_scatter_allgather(
if (vremote < comm_size) {
ptrdiff_t send_offset = vrank_tree_root * scatter_count * extent;
ptrdiff_t recv_offset = vremote_tree_root * scatter_count * extent;
recv_count = count - vremote_tree_root * scatter_count;
if (recv_count < 0)
recv_count = 0;
recv_count = rectify_diff(count, (size_t)(vremote_tree_root * scatter_count));
err = ompi_coll_base_sendrecv((char *)buf + send_offset,
curr_count, datatype, remote,
MCA_COLL_BASE_TAG_BCAST,
Expand All @@ -877,7 +883,7 @@ int ompi_coll_base_bcast_intra_scatter_allgather(
MCA_COLL_BASE_TAG_BCAST,
comm, &status, rank);
if (MPI_SUCCESS != err) { goto cleanup_and_return; }
recv_count = (int)(status._ucount / datatype_size);
recv_count = (size_t)(status._ucount / datatype_size);
curr_count += recv_count;
}

Expand Down Expand Up @@ -913,7 +919,7 @@ int ompi_coll_base_bcast_intra_scatter_allgather(
MCA_COLL_BASE_TAG_BCAST,
comm, &status));
if (MPI_SUCCESS != err) { goto cleanup_and_return; }
recv_count = (int)(status._ucount / datatype_size);
recv_count = (size_t)(status._ucount / datatype_size);
curr_count += recv_count;
}
}
Expand Down Expand Up @@ -988,8 +994,8 @@ int ompi_coll_base_bcast_intra_scatter_allgather_ring(
if (vrank & mask) {
int parent = (rank - mask + comm_size) % comm_size;
/* Compute an upper bound on recv block size */
recv_count = count - vrank * scatter_count;
if (recv_count <= 0) {
recv_count = rectify_diff(count, (size_t)(vrank * scatter_count));
if (0 == recv_count) {
curr_count = 0;
} else {
/* Recv data from parent */
Expand All @@ -1009,7 +1015,7 @@ int ompi_coll_base_bcast_intra_scatter_allgather_ring(
mask >>= 1;
while (mask > 0) {
if (vrank + mask < comm_size) {
send_count = curr_count - scatter_count * mask;
send_count = rectify_diff(curr_count, (size_t)(scatter_count * mask));
if (send_count > 0) {
int child = (rank + mask) % comm_size;
err = MCA_PML_CALL(send((char *)buf + (ptrdiff_t)scatter_count * (vrank + mask) * extent,
Expand All @@ -1023,33 +1029,41 @@ int ompi_coll_base_bcast_intra_scatter_allgather_ring(
mask >>= 1;
}

/* Allgather by a ring algorithm */
/* Allgather by a ring algorithm, using only unsigned types */
int left = (rank - 1 + comm_size) % comm_size;
int right = (rank + 1) % comm_size;

/* The block we will send/recv in each step */
int send_block = vrank;
int recv_block = (vrank - 1 + comm_size) % comm_size;

for (int i = 1; i < comm_size; i++) {
recv_count = (scatter_count < count - recv_block * scatter_count) ?
scatter_count : count - recv_block * scatter_count;
if (recv_count < 0)
recv_count = 0;
ptrdiff_t recv_offset = recv_block * scatter_count * extent;

send_count = (scatter_count < count - send_block * scatter_count) ?
scatter_count : count - send_block * scatter_count;
if (send_count < 0)
send_count = 0;
ptrdiff_t send_offset = send_block * scatter_count * extent;

err = ompi_coll_base_sendrecv((char *)buf + send_offset, send_count,
for (int i = 1; i < comm_size; ++i) {
/* how many elements remain in recv_block? */
size_t recv_offset_elems = recv_block * scatter_count;
size_t recv_remaining = rectify_diff(count, recv_offset_elems);
recv_count = (recv_remaining < scatter_count) ?
recv_remaining : scatter_count;
size_t recv_offset = recv_offset_elems * extent;

/* same logic for send */
size_t send_offset_elems = send_block * scatter_count;
size_t send_remaining = rectify_diff(count, send_offset_elems);
send_count = (send_remaining < scatter_count) ?
send_remaining : scatter_count;
size_t send_offset = send_offset_elems * extent;

err = ompi_coll_base_sendrecv((char*)buf + send_offset, send_count,
datatype, right, MCA_COLL_BASE_TAG_BCAST,
(char *)buf + recv_offset, recv_count,
(char*)buf + recv_offset, recv_count,
datatype, left, MCA_COLL_BASE_TAG_BCAST,
comm, MPI_STATUS_IGNORE, rank);
if (MPI_SUCCESS != err) { goto cleanup_and_return; }
if (MPI_SUCCESS != err) {
goto cleanup_and_return;
}

/* rotate blocks */
send_block = recv_block;
recv_block = (recv_block - 1 + comm_size) % comm_size;
recv_block = (recv_block + comm_size - 1) % comm_size;
}

cleanup_and_return:
Expand Down