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/*
* 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.spark.util.random
import org.scalatest.Matchers
import org.apache.commons.math3.stat.inference.ChiSquareTest
import org.apache.spark.SparkFunSuite
import org.apache.spark.util.Utils.times
import scala.language.reflectiveCalls
class XORShiftRandomSuite extends SparkFunSuite with Matchers {
def fixture: Object {val seed: Long; val hundMil: Int; val xorRand: XORShiftRandom} = new {
val seed = 1L
val xorRand = new XORShiftRandom(seed)
val hundMil = 1e8.toInt
}
/*
* This test is based on a chi-squared test for randomness.
*/
test ("XORShift generates valid random numbers") {
val f = fixture
val numBins = 10 // create 10 bins
val numRows = 5 // create 5 rows
val bins = Array.ofDim[Long](numRows, numBins)
// populate bins based on modulus of the random number for each row
for (r <- 0 to numRows-1) {
times(f.hundMil) {bins(r)(math.abs(f.xorRand.nextInt) % numBins) += 1}
}
/*
* Perform the chi square test on the 5 rows of randomly generated numbers evenly divided into
* 10 bins. chiSquareTest returns true iff the null hypothesis (that the classifications
* represented by the counts in the columns of the input 2-way table are independent of the
* rows) can be rejected with 100 * (1 - alpha) percent confidence, where alpha is prespeficied
* as 0.05
*/
val chiTest = new ChiSquareTest
assert(chiTest.chiSquareTest(bins, 0.05) === false)
}
test ("XORShift with zero seed") {
val random = new XORShiftRandom(0L)
assert(random.nextInt() != 0)
}
}
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