mirror of
https://github.com/gonum/gonum.git
synced 2025-10-24 15:43:07 +08:00
ec100cf00f
Improved function documentation Fixed dlarfb and dlarft and added full tests Added dgelq2 Working Dgels Fix many comments and tests Many PR comment responses Responded to more PR comments Many PR comments
77 lines
2.0 KiB
Go
77 lines
2.0 KiB
Go
// Copyright ©2015 The gonum Authors. All rights reserved.
|
||
// Use of this source code is governed by a BSD-style
|
||
// license that can be found in the LICENSE file.
|
||
|
||
package native
|
||
|
||
import (
|
||
"math"
|
||
|
||
"github.com/gonum/lapack"
|
||
)
|
||
|
||
// Dlange computes the matrix norm of the general m×n matrix a. The input norm
|
||
// specifies the norm computed.
|
||
// lapack.MaxAbs: the maximum absolute value of an element.
|
||
// lapack.MaxColumnSum: the maximum column sum of the absolute values of the entries.
|
||
// lapack.MaxRowSum: the maximum row sum of the absolute values of the entries.
|
||
// lapack.Frobenius: the square root of the sum of the squares of the entries.
|
||
// If norm == lapack.MaxColumnSum, work must be of length n, and this function will panic otherwise.
|
||
// There are no restrictions on work for the other matrix norms.
|
||
func (impl Implementation) Dlange(norm lapack.MatrixNorm, m, n int, a []float64, lda int, work []float64) float64 {
|
||
// TODO(btracey): These should probably be refactored to use BLAS calls.
|
||
checkMatrix(m, n, a, lda)
|
||
if m == 0 && n == 0 {
|
||
return 0
|
||
}
|
||
if norm == lapack.MaxAbs {
|
||
var value float64
|
||
for i := 0; i < m; i++ {
|
||
for j := 0; j < n; j++ {
|
||
value = math.Max(value, math.Abs(a[i*lda+j]))
|
||
}
|
||
}
|
||
return value
|
||
}
|
||
if norm == lapack.MaxColumnSum {
|
||
if len(work) < n {
|
||
panic(badWork)
|
||
}
|
||
for i := 0; i < n; i++ {
|
||
work[i] = 0
|
||
}
|
||
for i := 0; i < m; i++ {
|
||
for j := 0; j < n; j++ {
|
||
work[j] += math.Abs(a[i*lda+j])
|
||
}
|
||
}
|
||
var value float64
|
||
for i := 0; i < n; i++ {
|
||
value = math.Max(value, work[i])
|
||
}
|
||
return value
|
||
}
|
||
if norm == lapack.MaxRowSum {
|
||
var value float64
|
||
for i := 0; i < m; i++ {
|
||
var sum float64
|
||
for j := 0; j < n; j++ {
|
||
sum += math.Abs(a[i*lda+j])
|
||
}
|
||
value = math.Max(value, sum)
|
||
}
|
||
return value
|
||
}
|
||
if norm == lapack.NormFrob {
|
||
var value float64
|
||
scale := 0.0
|
||
sum := 1.0
|
||
for i := 0; i < m; i++ {
|
||
scale, sum = impl.Dlassq(n, a[i*lda:], 1, scale, sum)
|
||
}
|
||
value = scale * math.Sqrt(sum)
|
||
return value
|
||
}
|
||
panic("lapack: bad matrix norm")
|
||
}
|