/**
 * \file dnn/src/common/reduce_helper.h
 * 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.
 */
#pragma once
#include "megdnn/dtype.h"

#if MEGDNN_CC_HOST
#include "megdnn/basic_types.h"
#endif

namespace megdnn {
namespace reduce {

template <typename src_ctype, typename dst_ctype, typename wtype_>
struct SumOp {
    typedef wtype_ wtype;

    const wtype INIT;

    src_ctype* src;
    dst_ctype* dst;
    const size_t B;

    MEGDNN_HOST MEGDNN_DEVICE wtype read(uint32_t idx) { return src[idx]; }
    MEGDNN_HOST MEGDNN_DEVICE void write(uint32_t idx, wtype val) {
        dst[idx] = val;
    }
    static MEGDNN_HOST MEGDNN_DEVICE wtype apply(wtype lhs, wtype rhs) {
        return lhs + rhs;
    }
    MEGDNN_HOST MEGDNN_DEVICE SumOp(src_ctype* src, dst_ctype* dst, size_t B)
            : INIT(wtype(0)), src(src), dst(dst), B(B) {}
};

template <typename src_ctype, typename dst_ctype, typename wtype_>
struct MeanOp {
    typedef wtype_ wtype;

    const wtype INIT;

    src_ctype* src;
    dst_ctype* dst;
    const size_t B;

    MEGDNN_HOST MEGDNN_DEVICE wtype read(uint32_t idx) { return src[idx]; }
    MEGDNN_HOST MEGDNN_DEVICE void write(uint32_t idx, wtype val) {
        dst[idx] = val / static_cast<dst_ctype>(B);
    }
    static MEGDNN_HOST MEGDNN_DEVICE wtype apply(wtype lhs, wtype rhs) {
        return lhs + rhs;
    }
    MEGDNN_HOST MEGDNN_DEVICE MeanOp(src_ctype* src, dst_ctype* dst, size_t B)
            : INIT(wtype(0)), src(src), dst(dst), B(B) {}
};

template <typename src_ctype, typename dst_ctype, typename wtype_>
struct SumSqrOp {
    typedef wtype_ wtype;

    const wtype INIT;

    src_ctype* src;
    dst_ctype* dst;
    const size_t B;

    MEGDNN_HOST MEGDNN_DEVICE wtype read(uint32_t idx) {
        return static_cast<wtype>(src[idx]) * static_cast<wtype>(src[idx]);
    }
    MEGDNN_HOST MEGDNN_DEVICE void write(uint32_t idx, wtype val) {
        dst[idx] = val;
    }
    static MEGDNN_HOST MEGDNN_DEVICE wtype apply(wtype lhs, wtype rhs) {
        return lhs + rhs;
    }
    MEGDNN_HOST MEGDNN_DEVICE SumSqrOp(src_ctype* src, dst_ctype* dst, size_t B)
            : INIT(wtype(0)), src(src), dst(dst), B(B) {}
};

template <typename src_ctype, typename dst_ctype, typename wtype_>
struct ProdOp {
    typedef wtype_ wtype;
    const wtype INIT;

    src_ctype* src;
    dst_ctype* dst;
    const size_t B;

    MEGDNN_HOST MEGDNN_DEVICE wtype read(uint32_t idx) { return src[idx]; }
    MEGDNN_HOST MEGDNN_DEVICE void write(uint32_t idx, wtype val) {
        dst[idx] = val;
    }
    static MEGDNN_HOST MEGDNN_DEVICE wtype apply(wtype lhs, wtype rhs) {
        return lhs * rhs;
    }
    MEGDNN_HOST MEGDNN_DEVICE ProdOp(src_ctype* src, dst_ctype* dst, size_t B)
            : INIT(wtype(1)), src(src), dst(dst), B(B) {}
};

template <typename src_ctype, typename dst_ctype, typename wtype_>
struct MinOp {
    typedef wtype_ wtype;
    const wtype INIT;

    src_ctype* src;
    dst_ctype* dst;
    const size_t B;

    MEGDNN_HOST MEGDNN_DEVICE wtype read(uint32_t idx) { return src[idx]; }
    MEGDNN_HOST MEGDNN_DEVICE void write(uint32_t idx, wtype val) {
        dst[idx] = val;
    }
    static MEGDNN_HOST MEGDNN_DEVICE wtype apply(wtype lhs, wtype rhs) {
#if defined(__CUDA_ARCH__)
        return lhs < rhs ? lhs : rhs;
#else
        return std::min(lhs, rhs);
#endif
    }
    MEGDNN_HOST MEGDNN_DEVICE MinOp(src_ctype* src, dst_ctype* dst, size_t B)
            : INIT(wtype(DTypeTrait<wtype>::max())), src(src), dst(dst), B(B) {}
};

template <typename src_ctype, typename dst_ctype, typename wtype_>
struct MaxOp {
    typedef wtype_ wtype;
    const wtype INIT;

    src_ctype* src;
    dst_ctype* dst;
    const size_t B;

    MEGDNN_HOST MEGDNN_DEVICE wtype read(uint32_t idx) { return src[idx]; }
    MEGDNN_HOST MEGDNN_DEVICE void write(uint32_t idx, wtype val) {
        dst[idx] = val;
    }
    static MEGDNN_HOST MEGDNN_DEVICE wtype apply(wtype lhs, wtype rhs) {
#if defined(__CUDA_ARCH__)
        return lhs > rhs ? lhs : rhs;
#else
        return std::max(lhs, rhs);
#endif
    }
    MEGDNN_HOST MEGDNN_DEVICE MaxOp(src_ctype* src, dst_ctype* dst, size_t B)
            : INIT(wtype(DTypeTrait<wtype>::min())), src(src), dst(dst), B(B) {}
};

#if MEGDNN_CC_HOST
void get_ABC(const TensorShape& shape, size_t& A, size_t& B, size_t& C,
             size_t axis);
#endif

}  // namespace reduce
}  // namespace megdnn
// vim: syntax=cpp.doxygen