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// Copyright (c) 2022 PaddlePaddle Authors. 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.
// clang-format will try to sort headers according to google c++ style,
// and that cause compiling problems.
// clang-format off
#include "paddle/phi/kernels/gelu_kernel.h"
#include "paddle/phi/backends/gpu/gpu_context.h"
#include "paddle/phi/common/amp_type_traits.h"
#include "paddle/phi/core/dense_tensor.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/broadcast_function.h"
#include "paddle/phi/kernels/gpu/gelu_funcs.h"
// clang-format on
COMMON_DECLARE_bool(use_fast_math);
COMMON_DECLARE_bool(use_accuracy_compatible_kernel);
namespace phi {
template <typename T>
struct GeluWithApproximateFunctor {
using MT = typename MPTypeTrait<T>::Type;
inline HOSTDEVICE T operator()(T arg_x) {
// this function is tanh approximation of gelu
MT x = static_cast<MT>(arg_x);
MT one = static_cast<MT>(1);
MT half = static_cast<MT>(0.5);
MT kAlpha = M_SQRT2 * M_2_SQRTPI * MT(0.5);
auto tanh_out =
tanh(kAlpha * (x + static_cast<MT>(GELU_CONSTANT) * (x * x * x)));
MT out = half * x * (one + tanh_out);
return static_cast<T>(out);
}
};
template <typename T>
struct GeluWithoutApproximateFunctor {
using MT = typename MPTypeTrait<T>::Type;
inline HOSTDEVICE T operator()(T arg_x) {
// actual gelu with approximation = false
MT x = static_cast<MT>(arg_x);
// return static_cast<T>(x * normcdf(x));
constexpr MT kAlpha = M_SQRT1_2;
return static_cast<T>(x * MT(0.5) * (MT(1) + std::erf(x * kAlpha)));
}
};
template <typename T, typename Context>
void GeluKernel(const Context& dev_ctx,
const DenseTensor& x,
bool approximate,
DenseTensor* out) {
dev_ctx.template Alloc<T>(out);
if (out && out->numel() == 0) {
return;
}
std::vector<const DenseTensor*> ins = {&x};
std::vector<DenseTensor*> outs = {out};
if (approximate) {
#if defined(__NVCC__) || defined(__HIPCC__)
if (std::is_same<T, dtype::float16>::value &&
!FLAGS_use_accuracy_compatible_kernel) {
size_t n = x.numel();
const auto* in_ptr = reinterpret_cast<const __half*>(x.data<T>());
auto* out_ptr = reinterpret_cast<__half*>(out->data<T>());
if (TryLaunchFP16FastGeluFwdVectorizeCUDAKernel(
dev_ctx, in_ptr, out_ptr, n)) {
return;
}
}
#endif
using Functor = GeluWithApproximateFunctor<T>;
funcs::ElementwiseKernel<T, Functor, 1>(dev_ctx, ins, &outs, Functor());
} else {
using Functor = GeluWithoutApproximateFunctor<T>;
funcs::ElementwiseKernel<T, Functor, 1>(dev_ctx, ins, &outs, Functor());
}
}
} // namespace phi
PD_REGISTER_KERNEL(gelu,
GPU,
ALL_LAYOUT,
phi::GeluKernel,
float,
double,
phi::float16,
phi::bfloat16) {}