forked from LaconicNetwork/kompose
30 lines
904 B
Go
30 lines
904 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 "math"
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// Dlassq updates a sum of squares in scaled form. The input parameters scale and
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// sumsq represent the current scale and total sum of squares. These values are
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// updated with the information in the first n elements of the vector specified
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// by x and incX.
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func (impl Implementation) Dlassq(n int, x []float64, incx int, scale float64, sumsq float64) (scl, smsq float64) {
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if n <= 0 {
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return scale, sumsq
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}
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for ix := 0; ix <= (n-1)*incx; ix += incx {
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absxi := math.Abs(x[ix])
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if absxi > 0 || math.IsNaN(absxi) {
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if scale < absxi {
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sumsq = 1 + sumsq*(scale/absxi)*(scale/absxi)
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scale = absxi
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} else {
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sumsq += (absxi / scale) * (absxi / scale)
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}
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}
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}
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return scale, sumsq
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}
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