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48 lines
1012 B
Go
48 lines
1012 B
Go
// Copyright ©2015 The gonum Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package native
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import (
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"math"
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"gonum.org/v1/gonum/blas/blas64"
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)
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// Drscl multiplies the vector x by 1/a being careful to avoid overflow or
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// underflow where possible.
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//
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// Drscl is an internal routine. It is exported for testing purposes.
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func (impl Implementation) Drscl(n int, a float64, x []float64, incX int) {
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checkVector(n, x, incX)
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bi := blas64.Implementation()
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cden := a
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cnum := 1.0
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smlnum := dlamchS
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bignum := 1 / smlnum
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for {
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cden1 := cden * smlnum
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cnum1 := cnum / bignum
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var mul float64
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var done bool
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switch {
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case cnum != 0 && math.Abs(cden1) > math.Abs(cnum):
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mul = smlnum
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done = false
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cden = cden1
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case math.Abs(cnum1) > math.Abs(cden):
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mul = bignum
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done = false
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cnum = cnum1
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default:
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mul = cnum / cden
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done = true
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}
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bi.Dscal(n, mul, x, incX)
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if done {
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break
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}
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}
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}
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