/**
 * \file dnn/src/cuda/convolution/backward_filter/matmul.cpp
 * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
 *
 * Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 */

#include "./algo.h"
#include "src/cuda/utils.h"
#include "src/cuda/convolution/helper.h"
#include "src/cuda/convolution/im2col.cuh"

using namespace megdnn;
using namespace cuda;

bool ConvolutionBackwardFilterImpl::AlgoMatmul::is_available(
        const SizeArgs &args) const {
    auto &&fm = args.grad_filter_meta;
    return fm.format == Param::Format::NCHW &&
           args.diff_layout->dtype.category() == DTypeCategory::FLOAT &&
           fm.group == 1 && fm.spatial_ndim == 2;
}

size_t ConvolutionBackwardFilterImpl::AlgoMatmul::get_workspace_in_bytes(
        const SizeArgs &args) const {
    return matmul_get_workspace_bundle(
            args.as_fwd_args()).total_size_in_bytes();
}

void ConvolutionBackwardFilterImpl::AlgoMatmul::exec(
        const ExecArgs &args) const {
#define cb(DType) \
    if (args.diff_layout->dtype == DType()) { \
        using ctype = typename DTypeTrait<DType>::ctype; \
        exec_internal<ctype>(args); \
        return; \
    }
    MEGDNN_FOREACH_COMPUTING_DTYPE_FLOAT(cb)
#undef cb

    megdnn_assert_internal(0);
}

template<typename T>
void ConvolutionBackwardFilterImpl::AlgoMatmul::exec_internal(
        const ExecArgs &args) {
    auto &&fm = args.grad_filter_meta;
    size_t N = args.src_layout->shape[0],
           IC = fm.icpg,
           IH = args.src_layout->shape[2],
           IW = args.src_layout->shape[3],
           OC = fm.ocpg,
           OH = args.diff_layout->shape[2],
           OW = args.diff_layout->shape[3],
           FH = fm.spatial[0],
           FW = fm.spatial[1],
           PH = fm.padding[0],
           PW = fm.padding[1],
           SH = fm.stride[0],
           SW = fm.stride[1],
           DH = fm.dilation[0],
           DW = fm.dilation[1];
    auto stream = cuda_stream(args.handle);
    auto wbundle = matmul_get_workspace_bundle(args.as_fwd_args());
    wbundle.set(args.workspace.raw_ptr);
    T *diff_t = static_cast<T *>(wbundle.get(0));
    T *col = static_cast<T *>(wbundle.get(1));
    {
        // transpose diff
        TensorLayout froml({N, OC*OH*OW}, typename DTypeTrait<T>::dtype()),
                     tol(froml);
        froml.stride[0] = args.diff_layout->stride[0];
        tol.stride[0] = 1;
        tol.stride[1] = N;
        TensorND from(args.diff_tensor->ptr<T>(), froml),
                 to(diff_t, tol);
        args.handle->relayout_opr()->exec(from, to);
    }
    {
        // im2col
        convolution::im2col<T>(args.src_tensor->ptr<T>(), col,
                N, args.src_tensor->layout.stride[0],
                IC, IH, IW,
                FH, FW,
                OH, OW,
                PH, PW,
                SH, SW,
                DH, DW,
                stream);
    }
    {
        // take gemm grad
        TensorLayout Al({OC, IC*FH*FW}, typename DTypeTrait<T>::dtype()),
                     Bl({IC*FH*FW, OH*OW*N}, typename DTypeTrait<T>::dtype()),
                     Cl({OC, OH*OW*N}, typename DTypeTrait<T>::dtype());
        TensorND A(args.grad_tensor->ptr<T>(), Al),
                 B(col, Bl),
                 C(diff_t, Cl);
        if (fm.should_flip) {
            A.raw_ptr = wbundle.get(2);
        }
        auto&& matmul_opr = args.handle->create_operator<MatrixMulForward>();
        if (args.opr->param().compute_mode ==
            param::Convolution::ComputeMode::FLOAT32) {
            matmul_opr->param().compute_mode =
                    param::MatrixMul::ComputeMode::FLOAT32;
        }
        matmul_opr->param().transposeB = true;
        megdnn_assert(matmul_opr->get_workspace_in_bytes(C.layout, B.layout,
                                                         A.layout) == 0_z,
                      "Assume matmul opr in algo MATMUL doesn't need extra "
                      "workspace");
        matmul_opr->exec(C, B, A, Workspace());

        if (fm.should_flip) {
            convolution::flip_filter(
                    args.as_fwd_args(),
                    {static_cast<dt_byte*>(args.grad_tensor->raw_ptr),
                    wbundle.get_size(2)},
                    A.raw_ptr
                    );
        }
    }
}

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