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Single precision histograms on GPU (#3965)

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* Allow single precision histogram summation in gpu_hist

* Add python test, reduce run-time of gpu_hist tests

* Update documentation
This commit is contained in:
Rory Mitchell
2018-12-10 10:55:30 +13:00
committed by GitHub
parent 9af6b689d6
commit 93f9ce9ef9
10 changed files with 351 additions and 212 deletions
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26
src/common/device_helpers.cuh
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@@ -944,6 +944,32 @@ class AllReducer {
#endif
}
/**
* \brief Allreduce. Use in exactly the same way as NCCL but without needing
* streams or comms.
*
* \param communication_group_idx Zero-based index of the communication group.
* \param sendbuff The sendbuff.
* \param recvbuff The recvbuff.
* \param count Number of elements.
*/
void AllReduceSum(int communication_group_idx, const float *sendbuff,
float *recvbuff, int count) {
#ifdef XGBOOST_USE_NCCL
CHECK(initialised_);
dh::safe_cuda(cudaSetDevice(device_ordinals.at(communication_group_idx)));
dh::safe_nccl(ncclAllReduce(sendbuff, recvbuff, count, ncclFloat, ncclSum,
comms.at(communication_group_idx),
streams.at(communication_group_idx)));
if(communication_group_idx == 0)
{
allreduce_bytes_ += count * sizeof(float);
allreduce_calls_ += 1;
}
#endif
}
/**
* \brief Allreduce. Use in exactly the same way as NCCL but without needing streams or comms.
*

24
src/common/hist_util.cu
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@@ -116,19 +116,19 @@ struct GPUSketcher {
n_rows_(row_end - row_begin), param_(std::move(param)) {
}
void Init(const SparsePage& row_batch, const MetaInfo& info) {
void Init(const SparsePage& row_batch, const MetaInfo& info, int gpu_batch_nrows) {
num_cols_ = info.num_col_;
has_weights_ = info.weights_.Size() > 0;
// find the batch size
if (param_.gpu_batch_nrows == 0) {
if (gpu_batch_nrows == 0) {
// By default, use no more than 1/16th of GPU memory
gpu_batch_nrows_ = dh::TotalMemory(device_) /
(16 * num_cols_ * sizeof(Entry));
} else if (param_.gpu_batch_nrows == -1) {
} else if (gpu_batch_nrows == -1) {
gpu_batch_nrows_ = n_rows_;
} else {
gpu_batch_nrows_ = param_.gpu_batch_nrows;
gpu_batch_nrows_ = gpu_batch_nrows;
}
if (gpu_batch_nrows_ > n_rows_) {
gpu_batch_nrows_ = n_rows_;
@@ -346,7 +346,8 @@ struct GPUSketcher {
}
};
void Sketch(const SparsePage& batch, const MetaInfo& info, HistCutMatrix* hmat) {
void Sketch(const SparsePage& batch, const MetaInfo& info,
HistCutMatrix* hmat, int gpu_batch_nrows) {
// create device shards
shards_.resize(dist_.Devices().Size());
dh::ExecuteIndexShards(&shards_, [&](int i, std::unique_ptr<DeviceShard>& shard) {
@@ -358,10 +359,11 @@ struct GPUSketcher {
});
// compute sketches for each shard
dh::ExecuteIndexShards(&shards_, [&](int idx, std::unique_ptr<DeviceShard>& shard) {
shard->Init(batch, info);
shard->Sketch(batch, info);
});
dh::ExecuteIndexShards(&shards_,
[&](int idx, std::unique_ptr<DeviceShard>& shard) {
shard->Init(batch, info, gpu_batch_nrows);
shard->Sketch(batch, info);
});
// merge the sketches from all shards
// TODO(canonizer): do it in a tree-like reduction
@@ -390,9 +392,9 @@ struct GPUSketcher {
void DeviceSketch
(const SparsePage& batch, const MetaInfo& info,
const tree::TrainParam& param, HistCutMatrix* hmat) {
const tree::TrainParam& param, HistCutMatrix* hmat, int gpu_batch_nrows) {
GPUSketcher sketcher(param, info.num_row_);
sketcher.Sketch(batch, info, hmat);
sketcher.Sketch(batch, info, hmat, gpu_batch_nrows);
}
} // namespace common

2
src/common/hist_util.h
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@@ -72,7 +72,7 @@ struct HistCutMatrix {
/*! \brief Builds the cut matrix on the GPU */
void DeviceSketch
(const SparsePage& batch, const MetaInfo& info,
const tree::TrainParam& param, HistCutMatrix* hmat);
const tree::TrainParam& param, HistCutMatrix* hmat, int gpu_batch_nrows);
/*!
* \brief A single row in global histogram index.