org.nd4j.linalg.api.iter.LinearIndexLookup Maven / Gradle / Ivy
package org.nd4j.linalg.api.iter;
import org.nd4j.linalg.api.shape.Shape;
import org.nd4j.linalg.util.ArrayUtil;
import java.io.Serializable;
/**
* Represents a cache linear index lookup
* @author Adam Gibson
*/
public class LinearIndexLookup implements Serializable {
private char ordering;
private int[][] indexes;
private int[] shape;
private boolean[] exists;
private int numIndexes;
/**
*
* @param shape the shape of the linear index
* @param ordering the ordering of the linear index
*/
public LinearIndexLookup(int[] shape, char ordering) {
this.shape = shape;
this.ordering = ordering;
numIndexes = ArrayUtil.prod(shape);
indexes = new int[numIndexes][shape.length];
exists = new boolean[numIndexes];
}
/**
* Give back a sub
* wrt the given linear index
* @param index the index
* @return the sub for the given index
*/
public int[] lookup(int index) {
if (exists[index]) {
return indexes[index];
} else {
exists[index] = true;
indexes[index] = ordering == 'c' ? Shape.ind2subC(shape, index, numIndexes)
: Shape.ind2sub(shape, index, numIndexes);
return indexes[index];
}
}
}