/*
* 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 water.MRTask;
import water.fvec.Frame;
import water.fvec.Vec;
import water.fvec.Chunk;
import org.apache.mahout.h2obindings.drm.H2ODrm;
/**
* R-like cbind like operator, on two DRMs
*/
public class Cbind {
/**
* Combine the columns of two DRMs A and B to create a new DRM.
*
* @param drmA DRM representing matrix A.
* @param drmB DRM representing matrix B.
* @return new DRM containing columns of A and B adjacent.
*/
public static H2ODrm exec(H2ODrm drmA, H2ODrm drmB) {
Frame fra = drmA.frame;
Vec keysa = drmA.keys;
Frame frb = drmB.frame;
Vec keysb = drmB.keys;
// If A and B are similarly partitioned, ..
if (fra.anyVec().group() == frb.anyVec().group()) {
// .. then, do a light weight zip()
return zip(fra, keysa, frb, keysb);
} else {
// .. else, do a heavy weight join() which involves moving data over the wire
return join(fra, keysa, frb, keysb);
}
}
/** Light weight zip(), no data movement */
private static H2ODrm zip(final Frame fra, final Vec keysa, final Frame frb, final Vec keysb) {
// Create a new Vec[] to hold the concatenated list of A and B's column vectors
Vec vecs[] = new Vec[fra.vecs().length + frb.vecs().length];
int d = 0;
// fill A's column vectors
for (Vec vfra : fra.vecs()) {
vecs[d++] = vfra;
}
// and B's
for (Vec vfrb : frb.vecs()) {
vecs[d++] = vfrb;
}
// and create a new Frame with the combined list of column Vecs
Frame fr = new Frame(vecs);
/* Finally, inherit A's string labels into the result */
return new H2ODrm(fr, keysa);
}
/** Heavy weight join(), involves moving data */
private static H2ODrm join(final Frame fra, final Vec keysa, final Frame frb, final Vec keysb) {
// The plan is to re-organize B to be "similarly partitioned as A", and then zip()
Vec bvecs[] = new Vec[frb.vecs().length];
for (int i = 0; i < bvecs.length; i++) {
// First create column Vecs which are similarly partitioned as A
bvecs[i] = fra.anyVec().makeZero();
}
// Next run an MRTask on the new vectors, and fill each cell (initially 0)
// by pulling in appropriate values from B (frb)
new MRTask() {
public void map(Chunk chks[]) {
int chunkSize = chks[0].len();
long start = chks[0].start();
Vec vecs[] = frb.vecs();
for (int r = 0; r < chunkSize; r++) {
for (int c = 0; c < chks.length; c++) {
// assert va.atStr(start+r) == vb.atStr(start+r)
chks[c].set0(r, vecs[c].at(start + r));
}
}
}
}.doAll(bvecs);
// now that bvecs[] is compatible, just zip'em'up
return zip(fra, keysa, new Frame(bvecs), null);
}
}