Files
2026-07-13 13:33:03 +08:00

107 lines
3.6 KiB
C++

//
// ReduceGrad.cpp
// MNN
//
// Created by MNN on 2019/05/24.
// Copyright © 2018, Alibaba Group Holding Limited
//
#include "OpGrad.hpp"
using namespace std;
namespace MNN {
using namespace MNN::Express;
class ReduceGrad : public OpGrad {
public:
virtual std::vector<Express::VARP> onGrad(Express::EXPRP expr,
const std::vector<Express::VARP>& backwardOutput) override {
std::vector<Express::VARP> result;
auto inputs = expr->inputs();
result.resize(inputs.size());
std::unique_ptr<OpT> forwardOp(expr->get()->UnPack());
std::vector<int> reductionDims = forwardOp->main.AsReductionParam()->dim;
auto keepDim = forwardOp->main.AsReductionParam()->keepDims;
if (inputs.size() > 1) {
reductionDims.clear();
auto ptr = inputs[1]->readMap<int32_t>();
auto shape = inputs[1]->getInfo();
for (int i = 0; i < shape->size; ++i) {
reductionDims.emplace_back(ptr[i]);
}
}
if (reductionDims.empty()) {
auto shape = inputs[0]->getInfo();
for (int i = 0; i < shape->dim.size(); ++i) {
reductionDims.emplace_back(i);
}
}
VARP mask = _ZerosLike(inputs[0]) + _Scalar<float>(1.0f);
auto outputDiff = backwardOutput[0];
// implement other reduction op's grad below
if (forwardOp->main.AsReductionParam()->operation == ReductionType_SUM) {
// do not need to modify grads, just copy them, so, pass
}
if (forwardOp->main.AsReductionParam()->operation == ReductionType_MEAN) {
auto gradCount = _Size(outputDiff);
auto inputCount = _Size(inputs[0]);
outputDiff = _Multiply(outputDiff, _Cast<float>(gradCount) / _Cast<float>(inputCount));
}
if (forwardOp->main.AsReductionParam()->operation == ReductionType_MAXIMUM) {
auto output = Variable::create(expr);
if (!keepDim) {
output = _Unsqueeze(output, reductionDims);
}
mask = _Sign(inputs[0] - output) + _Scalar<float>(1.0f);
mask = mask / _ReduceSum(mask);
}
if (forwardOp->main.AsReductionParam()->operation == ReductionType_MINIMUM) {
auto output = Variable::create(expr);
if (!keepDim) {
output = _Unsqueeze(output, reductionDims);
}
mask = _Sign(output - inputs[0]) + _Scalar<float>(1.0f);
mask = mask / _ReduceSum(mask);
}
if (forwardOp->main.AsReductionParam()->operation == ReductionType_PROD) {
auto output = Variable::create(expr);
if (!keepDim) {
output = _Unsqueeze(output, reductionDims);
}
mask = output / inputs[0];
}
// this should be common operations, to expand grads to inputs shape
if (!keepDim) {
outputDiff = _Unsqueeze(outputDiff, reductionDims);
}
result[0] = mask * outputDiff;
return result;
}
};
class FillGrad : public OpGrad {
public:
virtual std::vector<Express::VARP> onGrad(Express::EXPRP expr,
const std::vector<Express::VARP>& backwardOutput) override {
return {backwardOutput[0].sum({})};
}
};
static void _create() {
static ReduceGrad _c;
OpGrad::insert(OpType_Reduction, &_c);
static FillGrad _d;
OpGrad::insert(OpType_Fill, &_d);
}
REGISTER_GRAD(ReduceGrad_cpp, _create);
};