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Pack bootstrapAllGathers in ncclCommSplit #1157

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Pack bootstrapAllGathers in ncclCommSplit #1157

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25 changes: 13 additions & 12 deletions src/init.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1301,29 +1301,31 @@ struct ncclCommFinalizeAsyncJob {
NCCL_PARAM(CommSplitShareResources, "COMM_SPLIT_SHARE_RESOURCES", NCCL_CONFIG_UNDEF_INT);

static ncclResult_t commGetSplitInfo(struct ncclComm* comm, struct ncclComm* parent, int color, int key, int* nRanksRet, int* myRankRet, int* parentRanksRet) {
int* colors = NULL;
int* keys = NULL;
int nRanks = 0, myRank = 0;
ncclResult_t ret = ncclSuccess;

NCCLCHECKGOTO(ncclCalloc(&colors, parent->nRanks), ret, fail);
NCCLCHECKGOTO(ncclCalloc(&keys, parent->nRanks), ret, fail);
struct colorKeyPair{
int color;
int key;
};
struct colorKeyPair* ckPairs = NULL;

NCCLCHECKGOTO(ncclCalloc(&ckPairs, parent->nRanks), ret, fail);

// Compute nRanks, my rank and the ranks (of the original comm) before and after me
colors[parent->rank] = color;
keys[parent->rank] = key;
NCCLCHECKGOTO(bootstrapAllGather(parent->bootstrap, colors, sizeof(int)), ret, fail);
NCCLCHECKGOTO(bootstrapAllGather(parent->bootstrap, keys, sizeof(int)), ret, fail);
ckPairs[parent->rank].color = color;
ckPairs[parent->rank].key = key;
NCCLCHECKGOTO(bootstrapAllGather(parent->bootstrap, ckPairs, sizeof(struct colorKeyPair)), ret, fail);

// Negative color does not create a new comm. Return now.
if (color == NCCL_SPLIT_NOCOLOR) goto exit;

memset(parentRanksRet, 0xff, sizeof(int) * parent->nRanks);
for (int i = 0; i < parent->nRanks; i++) {
if (colors[i] != color) continue;
if (ckPairs[i].color != color) continue;
// Find where to insert this rank
int insert = 0;
while (insert < nRanks && keys[parentRanksRet[insert]] <= keys[i]) insert++;
while (insert < nRanks && ckPairs[parentRanksRet[insert]].key <= ckPairs[i].key) insert++;
// Shift ranks by one after insert
for (int r = nRanks; r > insert; r--) parentRanksRet[r] = parentRanksRet[r - 1];
// Insert our rank
Expand All @@ -1339,8 +1341,7 @@ static ncclResult_t commGetSplitInfo(struct ncclComm* comm, struct ncclComm* par
*myRankRet = myRank;

exit:
free(colors);
free(keys);
free(ckPairs);
return ret;
fail:
goto exit;
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