Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/9229#discussion_r56207952
--- Diff: mllib/src/main/scala/org/apache/spark/ml/ann/Layer.scala ---
@@ -294,89 +248,13 @@ private[ann] object ActivationFunction {
}
/**
- * Implements SoftMax activation function
- */
-private[ann] class SoftmaxFunction extends ActivationFunction {
- override def eval(x: BDM[Double], y: BDM[Double]): Unit = {
- var j = 0
- // find max value to make sure later that exponent is computable
- while (j < x.cols) {
- var i = 0
- var max = Double.MinValue
- while (i < x.rows) {
- if (x(i, j) > max) {
- max = x(i, j)
- }
- i += 1
- }
- var sum = 0.0
- i = 0
- while (i < x.rows) {
- val res = Math.exp(x(i, j) - max)
- y(i, j) = res
- sum += res
- i += 1
- }
- i = 0
- while (i < x.rows) {
- y(i, j) /= sum
- i += 1
- }
- j += 1
- }
- }
-
- override def crossEntropy(
- output: BDM[Double],
- target: BDM[Double],
- result: BDM[Double]): Double = {
- def m(o: Double, t: Double): Double = o - t
- ActivationFunction(output, target, result, m)
- -Bsum( target :* Blog(output)) / output.cols
- }
-
- override def derivative(x: BDM[Double], y: BDM[Double]): Unit = {
- def sd(z: Double): Double = (1 - z) * z
- ActivationFunction(x, y, sd)
- }
-
- override def squared(output: BDM[Double], target: BDM[Double], result:
BDM[Double]): Double = {
- throw new UnsupportedOperationException("Sorry, squared error is not
defined for SoftMax.")
- }
-}
-
-/**
* Implements Sigmoid activation function
*/
private[ann] class SigmoidFunction extends ActivationFunction {
- override def eval(x: BDM[Double], y: BDM[Double]): Unit = {
- def s(z: Double): Double = Bsigmoid(z)
- ActivationFunction(x, y, s)
- }
- override def crossEntropy(
- output: BDM[Double],
- target: BDM[Double],
- result: BDM[Double]): Double = {
- def m(o: Double, t: Double): Double = o - t
- ActivationFunction(output, target, result, m)
- -Bsum(target :* Blog(output)) / output.cols
- }
+ override def eval: (Double) => Double = x => 1.0 / (1 + Math.exp(-x))
--- End diff --
Use `math` instead. `Math` is deprecated.
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