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From: eoriented <git@git.apache.org>
To: dev@horn.incubator.apache.org
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Subject: [GitHub] incubator-horn pull request: HORN-9: Add activations package
 and R...
Content-Type: text/plain
Message-Id: <20151117070417.F071EE0A3D@git1-us-west.apache.org>
Date: Tue, 17 Nov 2015 07:04:17 +0000 (UTC)

Github user eoriented commented on a diff in the pull request:

    https://github.com/apache/incubator-horn/pull/4#discussion_r45027621
  
    --- Diff: src/main/java/org/apache/horn/activations/Tanh.java ---
    @@ -0,0 +1,38 @@
    +/**
    + * 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.
    + */
    +package org.apache.horn.activations;
    +
    +import org.apache.hama.commons.math.DoubleFunction;
    +
    +/**
    + * Tanh function.
    + * 
    + */
    +public class Tanh extends DoubleFunction {
    +
    +  @Override
    +  public double apply(double value) {
    +    return Math.tanh(value);
    +  }
    +
    +  @Override
    +  public double applyDerivative(double value) {
    +    return 1 - Math.pow((Math.exp(2 * value) - 1) / (Math.exp(2 * value) + 1), 2);
    --- End diff --
    
    I think derivative of Tanh is more simple than this code.
    ```java
    return 1 - Math.pow(Math.tanh(value), 2);
    ```
    Would you mind modifying the code like above code?


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