nlpodyssey/spago

// Copyright 2022 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"
)

// Exp is an operator to perform element-wise base-e exponential function.
type Exp[O mat.Tensor] struct {
    x O
}

// NewExp returns a new Exp Function.
func NewExp[O mat.Tensor](x O) *Exp[O] {
    return &Exp[O]{
        x: x,
    }
}

// Operands returns the list of operands.
func (e *Exp[O]) Operands() []mat.Tensor {
    return []mat.Tensor{e.x}
}

// Forward computes the output of the function.
func (e *Exp[O]) Forward() (mat.Tensor, error) {
    return e.x.Value().(mat.Matrix).Exp(), nil
}

// Backward computes the backward pass.
func (e *Exp[O]) Backward(gy mat.Tensor) error {
    if !mat.SameDims(e.x.Value(), gy) {
        return fmt.Errorf("fn: matrices have incompatible dimensions")
    }
    if e.x.RequiresGrad() {
        gx := e.x.Value().(mat.Matrix).Exp()
        gx.ProdInPlace(gy.(mat.Matrix))
        e.x.AccGrad(gx)
    }
    return nil
}