/*
* 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.mahout.h2obindings.ops;
import org.apache.mahout.h2obindings.H2OHelper;
import org.apache.mahout.h2obindings.drm.H2ODrm;
import water.MRTask;
import water.fvec.Frame;
import water.fvec.Vec;
import water.fvec.Chunk;
/**
* Calculate A'A
*/
public class AtA {
/**
* Perform A'A operation on a DRM to create a new DRM.
*
* @param drmA DRM representing matrix A.
* @return new DRM containing A'A.
*/
public static H2ODrm exec(H2ODrm drmA) {
final Frame A = drmA.frame;
// First create an empty Frame of the required dimensions
Frame AtA = H2OHelper.emptyFrame(A.numCols(), A.numCols(), -1, -1);
// Execute MRTask on the new Frame, and fill each cell (initially 0) by
// computing appropriate values from A.
//
// chks.length == A.numCols()
new MRTask() {
public void map(Chunk chks[]) {
int chunkSize = chks[0].len();
long start = chks[0].start();
Vec A_vecs[] = A.vecs();
long A_rows = A.numRows();
for (int c = 0; c < chks.length; c++) {
for (int r = 0; r < chunkSize; r++) {
double v = 0;
for (long i = 0; i < A_rows; i++) {
v += (A_vecs[(int)(start + r)].at(i) * A_vecs[c].at(i));
}
chks[c].set0(r, v);
}
}
}
}.doAll(AtA);
// AtA is NOT similarly partitioned as A, drop labels
return new H2ODrm(AtA);
}
}