| #------------------------------------------------------------- |
| # |
| # Licensed to the Apache Software Foundation (ASF) under one |
| # or more contributor license agreements. See the NOTICE file |
| # distributed with this work for additional information |
| # regarding copyright ownership. The ASF licenses this file |
| # to you under the Apache License, Version 2.0 (the |
| # "License"); you may not use this file except in compliance |
| # with the License. You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, |
| # software distributed under the License is distributed on an |
| # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| # KIND, either express or implied. See the License for the |
| # specific language governing permissions and limitations |
| # under the License. |
| # |
| #------------------------------------------------------------- |
| |
| /* |
| * Exponential Linear Units (ELUs) nonlinearity layer. |
| */ |
| |
| forward = function(matrix[double] X, int alpha) |
| return (matrix[double] out) { |
| /* |
| * Computes the forward pass for a ELUs nonlinearity layer. |
| * Reference paper https://arxiv.org/abs/1511.07289v1 |
| * Performs an element-wise evaluation of |
| * `f(x) = x if x ≥ 0 else α (exp(x) − 1)`. |
| * |
| * Inputs: |
| * - X: Inputs, of shape (any, any). |
| * - alpha: Input, minimum value that the ELU can reach |
| * Typical value 1 |
| * |
| * Outputs: |
| * - out: Outputs, of same shape as `X`. |
| */ |
| out = max(0, X) + min(0, alpha * (exp(X) - 1)) |
| } |
| |
| backward = function(matrix[double] dout, matrix[double] X, int alpha) |
| return (matrix[double] dX) { |
| /* |
| * Computes the backward pass for a ELU nonlinearity layer. |
| * |
| * Inputs: |
| * - dout: Gradient wrt `out` from upstream, of same shape as `X`. |
| * - X: Previous input data matrix, of shape (any, any). |
| * - alpha: Minimum value that the ELU can reach |
| * Typical value 1 |
| * |
| * Outputs: |
| * - dX: Gradient wrt `X`, of same shape as `X`. |
| */ |
| dX = ((X > 0) + (X < 0) * (alpha * exp(X))) * dout |
| } |
| |