org.github.evenjn.numeric.NumericRandom Maven / Gradle / Ivy
/**
*
* Copyright 2016 Marco Trevisan
*
* Licensed 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.github.evenjn.numeric;
import java.util.Iterator;
import java.util.Random;
import java.util.function.Function;
import org.github.evenjn.yarn.Cursor;
import org.github.evenjn.yarn.SkipException;
import org.github.evenjn.yarn.SkipFold;
public class NumericRandom {
public static SkipFold filterPartition(
int partition_id,
int number_of_partitions,
boolean match_means_skip,
long seed ) {
Random random = new Random( seed );
return new SkipFold( ) {
@Override
public K next( K input )
throws SkipException {
if ( match_means_skip == ( random
.nextInt( number_of_partitions ) == partition_id ) ) {
throw SkipException.neo;
}
return input;
}
};
}
public static SkipFold filterBlockFraction(
int permille,
long seed ) {
Random random = new Random( seed );
return new SkipFold( ) {
@Override
public K next( K input )
throws SkipException {
if ( random.nextInt( 1000 ) < permille ) {
throw SkipException.neo;
}
return input;
}
};
}
public static SkipFold filterPassFraction(
int permille,
long seed ) {
Random random = new Random( seed );
return new SkipFold( ) {
@Override
public K next( K input )
throws SkipException {
if ( random.nextInt( 1000 ) < permille ) {
throw SkipException.neo;
}
return input;
}
};
}
public static RandomProbabilityMassGenerator generator( long seed ) {
return new RandomProbabilityMassGenerator( seed );
}
public static Function randomProbabilityMass(
long seed, int n ) {
final Random r = new Random( seed );
double[] values = new double[n];
double total = 0d;
for ( int i = 0; i < n; i++ ) {
double d = 0.01 + r.nextDouble( );
total += d;
values[i] = d;
}
for ( int i = 0; i < n; i++ ) {
values[i] = values[i] / total;
}
return x -> values[x];
}
public static class RandomProbabilityMassGenerator implements
Cursor {
private Random r;
private double total;
public RandomProbabilityMassGenerator(long seed) {
r = new Random( seed );
}
public Double next( ) {
double d = 0.01 + r.nextDouble( );
total += d;
return d;
}
public Double totalSoFar( ) {
return total;
}
public void resetTotal( ) {
total = 0;
}
}
public static Iterable randomRobin( long seed, int top ) {
Iterable result = new Iterable( ) {
public Iterator iterator( ) {
final Random r = new Random( seed );
return new Iterator( ) {
@Override
public Integer next( ) {
return r.nextInt( top );
}
@Override
public boolean hasNext( ) {
return true;
}
};
}
};
return result;
}
}