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CopyUtils.cuh
/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD+Patents license found in the
* LICENSE file in the root directory of this source tree.
*/
// Copyright 2004-present Facebook. All Rights Reserved.
#pragma once
#include "DeviceTensor.cuh"
#include "HostTensor.cuh"
namespace faiss { namespace gpu {
/// Ensure the memory at `p` is either on the given device, or copy it
/// to the device in a new allocation.
/// If `resources` is provided, then we will perform a temporary
/// memory allocation if needed. Otherwise, we will call cudaMalloc if
/// needed.
template <typename T, int Dim>
DeviceTensor<T, Dim, true> toDevice(GpuResources* resources,
int dstDevice,
T* src,
cudaStream_t stream,
std::initializer_list<int> sizes) {
int dev = getDeviceForAddress(src);
if (dev == dstDevice) {
// On device we expect
return DeviceTensor<T, Dim, true>(src, sizes);
} else {
// On different device or on host
DeviceScope scope(dstDevice);
Tensor<T, Dim, true> oldT(src, sizes);
if (resources) {
DeviceTensor<T, Dim, true> newT(resources->getMemoryManager(dstDevice),
sizes,
stream);
newT.copyFrom(oldT, stream);
return newT;
} else {
DeviceTensor<T, Dim, true> newT(sizes);
newT.copyFrom(oldT, stream);
return newT;
}
}
}
/// Copies a device array's allocation to an address, if necessary
template <typename T>
inline void fromDevice(T* src, T* dst, size_t num, cudaStream_t stream) {
// It is possible that the array already represents memory at `p`,
// in which case no copy is needed
if (src == dst) {
return;
}
int dev = getDeviceForAddress(dst);
if (dev == -1) {
CUDA_VERIFY(cudaMemcpyAsync(dst,
src,
num * sizeof(T),
cudaMemcpyDeviceToHost,
stream));
} else {
CUDA_VERIFY(cudaMemcpyAsync(dst,
src,
num * sizeof(T),
cudaMemcpyDeviceToDevice,
stream));
}
}
/// Copies a device array's allocation to an address, if necessary
template <typename T, int Dim>
void fromDevice(Tensor<T, Dim, true>& src, T* dst, cudaStream_t stream) {
FAISS_ASSERT(src.isContiguous());
fromDevice(src.data(), dst, src.numElements(), stream);
}
} } // namespace