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/*************************************************************************
* Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
*
* See LICENSE.txt for license information
************************************************************************/
#include "core.h"
#include "common_coll.h"
#include "enqueue.h"
#include "primitives.h"
#define NUM_SUBSTEPS 2
#define NUM_BUFCHUNKS 2
// Increase Step and poffset/noffset for buffer sync
#define NEXT_STEP \
step++; \
poffset = noffset; \
noffset += sliceSize; \
if (noffset == buffSize) noffset = 0;
#define ALIGN_SIZE(size, align) \
size = ((size + (align) - 1) / (align)) * (align);
template<int THREADS, int UNROLL, class FUNC, typename T>
__launch_bounds__(THREADS+WARP_SIZE, 1)
__global__ void AllGatherKernel(const KernelArgs<T> args) {
const int tid = threadIdx.x;
__shared__ T* sharedNextOutput;
__shared__ DevRing<T> ring;
bool pushrecv = args.pushrecv;
LoadRing<THREADS>(args.ring, &ring);
__syncthreads();
if (tid == 0) {
WaitFlag prevCommOp(ring.prevOpCounter, 0);
WaitFlag nextCommOp(ring.nextOpCounter, 0);
prevCommOp.wait(args.opIndex);
nextCommOp.wait(args.opIndex);
if (pushrecv) {
*ring.sendPtrToPrev = (T*)args.ThisOutput;
Wait([=] {
return *ring.recvPtrFromNext != nullptr;
});
sharedNextOutput = *ring.recvPtrFromNext;
*ring.recvPtrFromNext = nullptr;
}
}
__syncthreads();
WaitFlag waitDoneFromNext(ring.recvFlagFromNext, -NUM_BUFCHUNKS*NUM_SUBSTEPS);
WaitFlag waitReadyFromPrev(ring.recvFlagFromPrev, -1*NUM_SUBSTEPS);
PostFlag postDoneToPrev(ring.sendFlagToPrev, -1*NUM_SUBSTEPS);
PostFlag postReadyToNext(ring.sendFlagToNext, 0);
typedef Primitives<THREADS, UNROLL, NUM_SUBSTEPS, T> Prims;
const int size = args.N;
const int nranks = args.nRanks;
const int buffSize = args.buffSize / sizeof(T);
const int sliceSize = buffSize / NUM_BUFCHUNKS;
int step = 0;
int poffset, noffset = 0;
// Compute pointers
const T * __restrict__ thisInput = args.ThisInput;
T * __restrict__ thisOutput = args.ThisOutput;
T * __restrict__ prevInput = ring.recvBuffer;
T * __restrict__ nextOutput = ring.sendBuffer;
for (int chunkOffset = 0; chunkOffset < size; chunkOffset += sliceSize) {
/////////////// begin AllGather steps ///////////////
int offset;
int maxOffset = size-chunkOffset;
int rankDest;
// step 0: push data to next GPU
rankDest = ring.userRank[0];
offset = chunkOffset + rankDest * size;
if (thisInput == thisOutput) {
Prims::Copy(
thisInput + offset,
pushrecv ? sharedNextOutput + offset : nextOutput + noffset,
sliceSize, maxOffset,
step,
waitDoneFromNext, waitReadyFromPrev,
postReadyToNext, postDoneToPrev);
} else {
Prims::DoubleCopy(
thisInput + chunkOffset,
thisOutput + offset,
pushrecv ? sharedNextOutput + offset : nextOutput + noffset,
sliceSize, maxOffset,
step,
waitDoneFromNext, waitReadyFromPrev,
postReadyToNext, postDoneToPrev);
}
NEXT_STEP; // Increases step, poffset, noffset
// k-2 steps: copy to next GPU
if (pushrecv) {
for (int j=1; j<nranks-1; ++j) {
rankDest = ring.userRank[nranks-j];
offset = chunkOffset + rankDest * size;
Prims::Copy(
thisOutput + offset,
sharedNextOutput + offset,
sliceSize, maxOffset,
step,
waitDoneFromNext, waitReadyFromPrev,
postReadyToNext, postDoneToPrev);
NEXT_STEP;
}
} else {
for (int j=1; j<nranks-1; ++j) {
rankDest = ring.userRank[nranks-j];
offset = chunkOffset + rankDest * size;
Prims::DoubleCopy(
prevInput + poffset,
thisOutput + offset,
nextOutput + noffset,
sliceSize, maxOffset,
step,
waitDoneFromNext, waitReadyFromPrev,
postReadyToNext, postDoneToPrev);
NEXT_STEP;
}
// Make final copy from buffer to dest.
rankDest = ring.userRank[1];
offset = chunkOffset + rankDest * size;
// Here we need to copy from buffer to this output.
Prims::Copy(
prevInput + poffset,
thisOutput + offset,
sliceSize, maxOffset,
step,
waitDoneFromNext, waitReadyFromPrev,
postReadyToNext, postDoneToPrev);
NEXT_STEP;
}
}
// wait for the last data to be pushed to us
if (tid == 0) {
// Wait for last update from next then reset the flag
waitDoneFromNext.wait(NUM_SUBSTEPS*(step+NUM_BUFCHUNKS-1));
*ring.recvFlagFromNext = 0;
// Wait for last update from prev then reset the flag
waitReadyFromPrev.wait(NUM_SUBSTEPS*(step+1));
*ring.recvFlagFromPrev = 0;
incrementOpCounter(&args);
}
}
#define THREADS 512
#define UNROLL 8
template<class FUNC, typename T>
ncclResult_t RingAllGather(const void* sendbuff, void* recvbuff,
const int count, ncclComm* comm, cudaStream_t stream) {
if (comm->nRanks == 1) {
if (sendbuff != recvbuff)
CUDACHECK(cudaMemcpyAsync(recvbuff, sendbuff, count*sizeof(T), cudaMemcpyDeviceToDevice, stream), ncclUnhandledCudaError);
} else {
KernelArgs<T> args;
ArgsSetup(&args, sendbuff, recvbuff, 0, count, comm);
LAUNCH_KERNEL(AllGatherKernel, THREADS, UNROLL, FUNC, T, args, stream);
}
return ncclSuccess;
}
template<typename T, template<typename> class RedOp>
class AllGather {
public:
static ncclResult_t entry(const void* sendbuff, void* recvbuff,
int count, int /*root*/, ncclComm* comm, cudaStream_t stream) {
return RingAllGather<RedOp<T>, T>(sendbuff, recvbuff, count, comm, stream);
}
};
NCCL_API(ncclResult_t, ncclAllGather, const void* sendbuff, int count, ncclDataType_t datatype,
void* recvbuff, ncclComm_t comm, cudaStream_t stream);
ncclResult_t ncclAllGather(const void* sendbuff, int count, ncclDataType_t datatype,
void* recvbuff, ncclComm_t comm, cudaStream_t stream) {
NCCLCHECK(ArgsCheck(sendbuff, recvbuff, count, datatype, ncclSum, 0, comm, "AllGather"));
return enqueue<AllGather, FuncNull>(sendbuff, recvbuff, count, datatype, 0, comm, stream);
}
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