org.nd4j.linalg.api.iter.LinearIndexLookup Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2015-2018 Skymind, Inc.
*
* This program and the accompanying materials are made available under the
* terms of the Apache License, Version 2.0 which is available at
* https://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.
*
* SPDX-License-Identifier: Apache-2.0
******************************************************************************/
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 long[][] indexes;
private long[] shape;
private boolean[] exists;
private long numIndexes;
/**
*
* @param shape the shape of the linear index
* @param ordering the ordering of the linear index
*/
public LinearIndexLookup(int[] shape, char ordering) {
this(ArrayUtil.toLongArray(shape), ordering);
}
public LinearIndexLookup(long[] shape, char ordering) {
this.shape = shape;
this.ordering = ordering;
numIndexes = ArrayUtil.prodLong(shape);
// FIMXE: long!
indexes = new long[(int) numIndexes][shape.length];
exists = new boolean[(int) numIndexes];
}
/**
* Give back a sub
* wrt the given linear index
* @param index the index
* @return the sub for the given index
*/
public long[] 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];
}
}
}