nlpodyssey/spago

// Copyright 2019 spaGO Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gradfn

import (
    "fmt"

    "github.com/nlpodyssey/spago/mat"
)

// Add is an operator to perform element-wise sum over two values.
// y = x1 + x2
type Add[O mat.Tensor] struct {
    x1 O
    x2 O
}

// NewAdd returns a new Add Function.
func NewAdd[O mat.Tensor](x1, x2 O) *Add[O] {
    return &Add[O]{
        x1: x1,
        x2: x2,
    }
}

// Operands returns the list of operands.
func (r *Add[O]) Operands() []mat.Tensor {
    return []mat.Tensor{r.x1, r.x2}
}

// Forward computes the output of the function.
func (r *Add[O]) Forward() (mat.Tensor, error) {
    x1v := r.x1.Value().(mat.Matrix)
    x2v := r.x2.Value().(mat.Matrix)
    return x1v.Add(x2v), nil
}

// Backward computes the backward pass.
func (r *Add[O]) Backward(gy mat.Tensor) error {
    if r.x1.RequiresGrad() {
        x1v := r.x1.Value()
        if !mat.SameDims(x1v.(mat.Matrix), gy.(mat.Matrix)) {
            return fmt.Errorf("fn: matrices have incompatible dimensions")
        }
        r.x1.AccGrad(gy)
    }
    if r.x2.RequiresGrad() {
        x2v := r.x2.Value()
        if !mat.SameDims(x2v.(mat.Matrix), gy.(mat.Matrix)) {
            return fmt.Errorf("fn: matrices have incompatible dimensions")
        }
        r.x2.AccGrad(gy)
    }
    return nil
}