norm.go


// Copyright (c) Harri Rautila, 2013

// This file is part of github.com/hrautila/matops package. It is free software,
// distributed under the terms of GNU Lesser General Public License Version 3, or
// any later version. See the COPYING tile included in this archive.

package matops

import (
    "github.com/hrautila/matrix"
)

type Norms int
const (
    NORM_ONE = Norms(1)
    NORM_TWO = Norms(2)
    NORM_INF = Norms(-1)
)

func mNorm1(A *matrix.FloatMatrix) float64 {
    var amax float64 = 0.0
    var col matrix.FloatMatrix
    for k := 0; k < A.Cols(); k++ {
        col.SubMatrixOf(A, 0, k, A.Rows(), 1)
        cmax := ASum(&col)
        if cmax > amax {
            amax = cmax
        }
    }
    return amax
}

func mNormInf(A *matrix.FloatMatrix) float64 {
    var amax float64 = 0.0
    var row matrix.FloatMatrix
    for k := 0; k < A.Rows(); k++ {
        row.SubMatrixOf(A, k, 0, A.Cols(), 1)
        rmax := ASum(&row)
        if rmax > amax {
            amax = rmax
        }
    }
    return amax
}


/*
 * Compute matrix and vector norms.
 *
 * Arguments
 *  X    A real valued matrix or vector
 *
 *  norm Norm to compute
 *         NORM_ONE, NORM_TWO, NORM_INF
 *
 * Note: matrix NORM_TWO not yet implemented.
 */
func NormP(X *matrix.FloatMatrix, norm Norms) float64 {
    if isVector(X) {
        switch norm {
        case NORM_ONE:
            return ASum(X)
        case NORM_TWO:
            return Norm2(X)
        case NORM_INF:
            return AMax(X)
        }
        return 0.0
    }
    switch norm {
    case NORM_ONE:
        return mNorm1(X)
    case NORM_TWO:
        return 0.0
    case NORM_INF:
        return mNormInf(X)
    }
    return 0.0
}

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