org.ejml.dense.row.NormOps_CDRM Maven / Gradle / Ivy
/*
* Copyright (c) 2009-2017, Peter Abeles. All Rights Reserved.
*
* This file is part of Efficient Java Matrix Library (EJML).
*
* Licensed 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.ejml.dense.row;
import org.ejml.data.CMatrixRMaj;
/**
* @author Peter Abeles
*/
public class NormOps_CDRM {
/**
*
* Computes the Frobenius matrix norm:
*
* normF = Sqrt{ ∑i=1:m ∑j=1:n { aij2} }
*
*
* This is equivalent to the element wise p=2 norm.
*
*
* @param a The matrix whose norm is computed. Not modified.
* @return The norm's value.
*/
public static float normF( CMatrixRMaj a ) {
float total = 0;
float scale = CommonOps_CDRM.elementMaxAbs(a);
if( scale == 0.0f )
return 0.0f;
final int size = a.getDataLength();
for( int i = 0; i < size; i += 2 ) {
float real = a.data[i]/scale;
float imag = a.data[i+1]/scale;
total += real*real + imag*imag;
}
return scale* (float)Math.sqrt(total);
}
}