TensorRT-LLMs/cpp/tensorrt_llm/kernels/speculativeDecoding/medusaDecodingKernels.cu
2024-08-13 22:34:33 +08:00

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/*
* Copyright (c) 2024, NVIDIA CORPORATION. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "tensorrt_llm/common/assert.h"
#include "tensorrt_llm/common/cudaTypeUtils.cuh"
#include "tensorrt_llm/common/cudaUtils.h"
#include "tensorrt_llm/common/memoryUtils.h"
#include "tensorrt_llm/common/reduceKernelUtils.cuh"
#include "tensorrt_llm/kernels/speculativeDecoding/medusaDecodingKernels.h"
#ifndef CUDART_VERSION
#error CUDART_VERSION Undefined!
#elif (CUDART_VERSION >= 11050)
#include <cub/cub.cuh>
#else
#include "3rdparty/cub/cub.cuh"
#endif
using namespace tensorrt_llm::common;
using namespace tensorrt_llm::runtime;
namespace tensorrt_llm::kernels::speculative_decoding
{
namespace
{
__device__ __forceinline__ int4 reduceMaxInt4(int4 const& a, int4 const& b)
{
return a.x >= b.x ? a : b;
}
template <typename T, SizeType32 BLOCK_SIZE>
__global__ void acceptDraftTokensByIdsWithPaths(TokenIdType* outputIds, TokenIdType const* draftIds,
TokenIdType const* targetIds, SizeType32* sequenceLengths, SizeType32* acceptedLengths,
FinishedState* finishedFinal, SizeType32 const* batchSlots, SizeType32 const* paths, TokenIdType const* endIds,
T const** medusaLogits, T const** logitsPtrs, SizeType32* curTokensPerStep, SizeType32 const* targetTokensPerStep,
SizeType32* bestPathIds, SizeType32 batchSize, SizeType32 vocabSize, SizeType32 maxBatchSize, SizeType32 maxSeqLen,
SizeType32 maxNumHeads, SizeType32 maxDecodingTokens)
{
auto const batchIdx = static_cast<SizeType32>(blockIdx.x);
auto const batchSlot = batchSlots[batchIdx];
auto const inputLength = sequenceLengths[batchSlot];
auto const endId = endIds[batchSlot];
auto const numTokensPerStep = curTokensPerStep[batchSlot];
auto const maxNumDraftTokens = maxNumHeads + 1;
int4 partialMax{-1, -1, 0, 0};
// Go over different paths and construct implicit sequences
for (auto pathIdx = static_cast<SizeType32>(threadIdx.x); pathIdx < maxDecodingTokens;
pathIdx += static_cast<SizeType32>(blockDim.x))
{
auto acceptedLength = maxNumDraftTokens;
auto const pathOffset = flat_index3(batchSlot, pathIdx, 0, maxDecodingTokens, maxNumDraftTokens);
bool hasEnd = false;
auto const tokenId = paths[pathOffset];
// Continue if path does not exist
if (tokenId == -1)
{
continue;
}
auto const targetTokenIdx = batchSlot * maxDecodingTokens + tokenId;
auto targetToken = targetIds[targetTokenIdx];
auto nextIdx = tokenId;
// Go along the path
for (SizeType32 ti = 1; ti < maxNumDraftTokens; ++ti)
{
auto const tokenId = paths[pathOffset + ti];
// Break if path terminates
if (tokenId == -1)
{
hasEnd = targetToken == endId; // check if last token is EOS when path terminates.
acceptedLength = hasEnd ? ti - 1 : ti;
break;
}
auto const targetTokenIdx = batchSlot * maxDecodingTokens + tokenId;
auto const draftTokenIdx = batchSlot * (maxDecodingTokens - 1) + tokenId - 1;
// In context phase, no draft tokens are given. Set draft token to -1 to get guaranteed rejection
auto const draftToken = tokenId >= numTokensPerStep ? -1 : draftIds[draftTokenIdx];
// Check if draft tokens are the same as target tokens
bool const accepted = draftToken == targetToken;
hasEnd = targetToken == endId;
if (!accepted || hasEnd)
{
acceptedLength = hasEnd ? ti - 1 : ti;
break;
}
targetToken = targetIds[targetTokenIdx];
nextIdx = tokenId;
}
// Get longest path of the thread
if (partialMax.x < acceptedLength)
{
partialMax.x = acceptedLength;
partialMax.y = pathIdx;
partialMax.z = hasEnd;
partialMax.w = nextIdx;
}
}
// Get the longest path of the block (request)
typedef cub::BlockReduce<int4, BLOCK_SIZE> BlockReduce;
__shared__ typename BlockReduce::TempStorage tempStorage;
int4 total = BlockReduce(tempStorage).Reduce(partialMax, reduceMaxInt4);
__shared__ int4 totalShared;
if (threadIdx.x == 0)
{
totalShared = total;
}
__syncthreads();
auto const acceptedLength = totalShared.x;
auto const bestPathIdx = totalShared.y;
auto const bestNextIdx = numTokensPerStep == 1 ? 0 : totalShared.w;
auto const pathOffset = flat_index3(batchSlot, bestPathIdx, 0, maxDecodingTokens, maxNumDraftTokens);
for (auto ti = static_cast<SizeType32>(threadIdx.x); ti < acceptedLength; ti += static_cast<SizeType32>(blockDim.x))
{
auto const tokenId = paths[pathOffset + ti];
auto const targetSrcTokenIdx = batchSlot * maxDecodingTokens + tokenId;
auto const outputTokenIdx = batchSlot * maxSeqLen + inputLength + ti;
auto const targetToken = targetIds[targetSrcTokenIdx];
// Copy accepted tokens to the sequence with draft tokens (outputIds === outputIds)
outputIds[outputTokenIdx] = targetToken;
}
// Leading thread reconstructs winning path and sets new data
if (threadIdx.x == 0)
{
auto const hasEnd = totalShared.z;
// Set end condition
if (hasEnd)
{
finishedFinal[batchSlot].setFinishedEOS();
}
// Make correction to the sequence length
sequenceLengths[batchSlot] += acceptedLength;
acceptedLengths[batchSlot] = acceptedLength;
// In Medusa decoding step, number of draft tokens is 0 and must be updated for the next steps
if (numTokensPerStep == 1)
{
curTokensPerStep[batchSlot] = targetTokensPerStep[batchSlot];
}
bestPathIds[batchSlot] = bestPathIdx;
}
// Prepare logits pointers to respective logits from Medusa Heads for the all-top-K sampling kernel
for (auto hi = static_cast<SizeType32>(threadIdx.x); hi < maxNumHeads; hi += static_cast<SizeType32>(blockDim.x))
{
logitsPtrs[batchIdx * maxNumHeads + hi]
= medusaLogits[batchSlot * maxNumHeads + hi] + flat_index2(bestNextIdx, 0, vocabSize);
}
}
} // namespace
template <typename T>
void acceptDraftTokensByIdsWithPaths(TokenIdType* outputIds, TokenIdType const* draftIds, TokenIdType const* targetIds,
SizeType32* sequenceLengths, SizeType32* acceptedLengths, FinishedState* finishedFinal,
SizeType32 const* batchSlots, SizeType32 const* paths, TokenIdType const* endIds, T const** medusaLogits,
T const** logitsPtrs, SizeType32* curTokensPerStep, SizeType32 const* targetTokensPerStep, SizeType32* bestPathIds,
SizeType32 batchSize, SizeType32 vocabSize, SizeType32 maxBatchSize, SizeType32 maxSeqLen, SizeType32 maxNumHeads,
SizeType32 maxDecodingTokens, cudaStream_t stream)
{
constexpr SizeType32 BLOCK_SIZE = 256;
dim3 block(BLOCK_SIZE);
dim3 grid(batchSize);
acceptDraftTokensByIdsWithPaths<T, BLOCK_SIZE><<<grid, block, 0, stream>>>(outputIds, draftIds, targetIds,
sequenceLengths, acceptedLengths, finishedFinal, batchSlots, paths, endIds, medusaLogits, logitsPtrs,
curTokensPerStep, targetTokensPerStep, bestPathIds, batchSize, vocabSize, maxBatchSize, maxSeqLen, maxNumHeads,
maxDecodingTokens);
}
template void acceptDraftTokensByIdsWithPaths(TokenIdType* outputIds, TokenIdType const* draftIds,
TokenIdType const* targetIds, SizeType32* sequenceLengths, SizeType32* acceptedLengths,
FinishedState* finishedFinal, SizeType32 const* batchSlots, SizeType32 const* paths, TokenIdType const* endIds,
float const** medusaLogits, float const** logitsPtrs, SizeType32* curTokensPerStep,
SizeType32 const* targetTokensPerStep, SizeType32* bestPathIds, SizeType32 batchSize, SizeType32 vocabSize,
SizeType32 maxBatchSize, SizeType32 maxSeqLen, SizeType32 maxNumHeads, SizeType32 maxDecodingTokens,
cudaStream_t stream);
template void acceptDraftTokensByIdsWithPaths(TokenIdType* outputIds, TokenIdType const* draftIds,
TokenIdType const* targetIds, SizeType32* sequenceLengths, SizeType32* acceptedLengths,
FinishedState* finishedFinal, SizeType32 const* batchSlots, SizeType32 const* paths, TokenIdType const* endIds,
half const** medusaLogits, half const** logitsPtrs, SizeType32* curTokensPerStep,
SizeType32 const* targetTokensPerStep, SizeType32* bestPathIds, SizeType32 batchSize, SizeType32 vocabSize,
SizeType32 maxBatchSize, SizeType32 maxSeqLen, SizeType32 maxNumHeads, SizeType32 maxDecodingTokens,
cudaStream_t stream);
namespace
{
__global__ void scatterMedusaDraftTokens(TokenIdType* treeDraftIds, TokenIdType const* sourceDraftIds,
SizeType32 const* treeIds, SizeType32 const* tokensPerStepData, SizeType32 const* batchSlots,
SizeType32 maxDecodingTokens)
{
auto const batchIdx = static_cast<SizeType32>(blockIdx.x);
auto const batchSlot = batchSlots[batchIdx];
auto const tokensPerStep = tokensPerStepData[batchSlot];
auto const maxDecodingDraftTokens = maxDecodingTokens - 1;
for (auto index = static_cast<SizeType32>(threadIdx.x); index < tokensPerStep - 1;
index += static_cast<SizeType32>(blockDim.x))
{
auto const indexInTree = treeIds[batchSlot * maxDecodingDraftTokens + index];
auto const treeDraftIdx = batchSlot * maxDecodingDraftTokens + index;
auto const sourceDraftIdx = batchSlot * maxDecodingTokens + indexInTree;
treeDraftIds[treeDraftIdx] = sourceDraftIds[sourceDraftIdx];
}
}
} // namespace
void scatterMedusaDraftTokens(TokenIdType* treeDraftIds, TokenIdType const* sourceDraftIds, SizeType32 const* treeIds,
SizeType32 const* tokensPerStep, SizeType32 const* batchSlots, SizeType32 maxDecodingTokens, SizeType32 batchSize,
cudaStream_t stream)
{
constexpr SizeType32 BLOCK_SIZE = 256;
scatterMedusaDraftTokens<<<batchSize, BLOCK_SIZE, 0, stream>>>(
treeDraftIds, sourceDraftIds, treeIds, tokensPerStep, batchSlots, maxDecodingTokens);
}
} // namespace tensorrt_llm::kernels::speculative_decoding