org.apache.mahout.math.OrthonormalityVerifier.java Source code

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Here is the source code for org.apache.mahout.math.OrthonormalityVerifier.java

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/**
 * 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.math;

import com.google.common.collect.Lists;

import java.util.List;

public final class OrthonormalityVerifier {

    private OrthonormalityVerifier() {
    }

    public static VectorIterable pairwiseInnerProducts(Iterable<MatrixSlice> basis) {
        DenseMatrix out = null;
        for (MatrixSlice slice1 : basis) {
            List<Double> dots = Lists.newArrayList();
            for (MatrixSlice slice2 : basis) {
                dots.add(slice1.vector().dot(slice2.vector()));
            }
            if (out == null) {
                out = new DenseMatrix(dots.size(), dots.size());
            }
            for (int i = 0; i < dots.size(); i++) {
                out.set(slice1.index(), i, dots.get(i));
            }
        }
        return out;
    }

}