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119 lines
2.6 KiB
Go
119 lines
2.6 KiB
Go
// Copyright ©2017 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 testlapack
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import (
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"math"
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"math/rand"
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)
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// Dlatm1 computes the entries of dst as specified by mode, cond and rsign.
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//
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// mode describes how dst will be computed:
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// |mode| == 1: dst[0] = 1 and dst[1:n] = 1/cond
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// |mode| == 2: dst[:n-1] = 1/cond and dst[n-1] = 1
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// |mode| == 3: dst[i] = cond^{-i/(n-1)}, i=0,...,n-1
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// |mode| == 4: dst[i] = 1 - i*(1-1/cond)/(n-1)
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// |mode| == 5: dst[i] = random number in the range (1/cond, 1) such that
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// their logarithms are uniformly distributed
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// |mode| == 6: dst[i] = random number from the distribution given by dist
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// If mode is negative, the order of the elements of dst will be reversed.
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// For other values of mode Dlatm1 will panic.
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//
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// If rsign is true and mode is not ±6, each entry of dst will be multiplied by 1
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// or -1 with probability 0.5
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//
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// dist specifies the type of distribution to be used when mode == ±6:
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// dist == 1: Uniform[0,1)
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// dist == 2: Uniform[-1,1)
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// dist == 3: Normal(0,1)
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// For other values of dist Dlatm1 will panic.
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//
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// rnd is used as a source of random numbers.
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func Dlatm1(dst []float64, mode int, cond float64, rsign bool, dist int, rnd *rand.Rand) {
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amode := mode
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if amode < 0 {
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amode = -amode
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}
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if amode < 1 || 6 < amode {
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panic("testlapack: invalid mode")
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}
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if cond < 1 {
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panic("testlapack: cond < 1")
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}
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if amode == 6 && (dist < 1 || 3 < dist) {
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panic("testlapack: invalid dist")
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}
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n := len(dst)
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if n == 0 {
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return
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}
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switch amode {
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case 1:
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dst[0] = 1
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for i := 1; i < n; i++ {
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dst[i] = 1 / cond
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}
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case 2:
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for i := 0; i < n-1; i++ {
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dst[i] = 1
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}
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dst[n-1] = 1 / cond
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case 3:
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dst[0] = 1
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if n > 1 {
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alpha := math.Pow(cond, -1/float64(n-1))
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for i := 1; i < n; i++ {
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dst[i] = math.Pow(alpha, float64(i))
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}
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}
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case 4:
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dst[0] = 1
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if n > 1 {
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condInv := 1 / cond
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alpha := (1 - condInv) / float64(n-1)
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for i := 1; i < n; i++ {
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dst[i] = float64(n-i-1)*alpha + condInv
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}
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}
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case 5:
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alpha := math.Log(1 / cond)
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for i := range dst {
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dst[i] = math.Exp(alpha * rnd.Float64())
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}
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case 6:
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switch dist {
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case 1:
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for i := range dst {
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dst[i] = rnd.Float64()
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}
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case 2:
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for i := range dst {
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dst[i] = 2*rnd.Float64() - 1
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}
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case 3:
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for i := range dst {
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dst[i] = rnd.NormFloat64()
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}
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}
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}
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if rsign && amode != 6 {
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for i, v := range dst {
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if rnd.Float64() < 0.5 {
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dst[i] = -v
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}
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}
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}
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if mode < 0 {
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for i := 0; i < n/2; i++ {
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dst[i], dst[n-i-1] = dst[n-i-1], dst[i]
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}
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}
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}
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