/
dlascl.go
72 lines (68 loc) · 1.44 KB
/
dlascl.go
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// 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"
)
// Dlascl multiplies a rectangular matrix by a scalar.
func (impl Implementation) Dlascl(kind lapack.MatrixType, kl, ku int, cfrom, cto float64, m, n int, a []float64, lda int) {
checkMatrix(m, n, a, lda)
if cfrom == 0 {
panic("dlascl: zero divisor")
}
if math.IsNaN(cfrom) || math.IsNaN(cto) {
panic("dlascl: NaN scale factor")
}
if n == 0 || m == 0 {
return
}
smlnum := dlamchS
bignum := 1 / smlnum
cfromc := cfrom
ctoc := cto
cfrom1 := cfromc * smlnum
for {
var done bool
var mul, ctol float64
if cfrom1 == cfromc {
// cfromc is inf
mul = ctoc / cfromc
done = true
ctol = ctoc
} else {
ctol = ctoc / bignum
if ctol == ctoc {
// ctoc is either 0 or inf.
mul = ctoc
done = true
cfromc = 1
} else if math.Abs(cfrom1) > math.Abs(ctoc) && ctoc != 0 {
mul = smlnum
done = false
cfromc = cfrom1
} else if math.Abs(ctol) > math.Abs(cfromc) {
mul = bignum
done = false
ctoc = ctol
} else {
mul = ctoc / cfromc
done = true
}
}
switch kind {
default:
panic("lapack: not implemented")
case lapack.General:
for i := 0; i < m; i++ {
for j := 0; j < n; j++ {
a[i*lda+j] = a[i*lda+j] * mul
}
}
}
if done {
break
}
}
}