diff --git a/testlapack/matgen.go b/testlapack/matgen.go new file mode 100644 index 00000000..42868474 --- /dev/null +++ b/testlapack/matgen.go @@ -0,0 +1,118 @@ +// Copyright ©2017 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 testlapack + +import ( + "math" + "math/rand" +) + +// Dlatm1 computes the entries of dst as specified by mode, cond and rsign. +// +// mode describes how dst will be computed: +// |mode| == 1: dst[0] = 1 and dst[1:n] = 1/cond +// |mode| == 2: dst[:n-1] = 1/cond and dst[n-1] = 1 +// |mode| == 3: dst[i] = cond^{-i/(n-1)}, i=0,...,n-1 +// |mode| == 4: dst[i] = 1 - i*(1-1/cond)/(n-1) +// |mode| == 5: dst[i] = random number in the range (1/cond, 1) such that +// their logarithms are uniformly distributed +// |mode| == 6: dst[i] = random number from the distribution given by dist +// If mode is negative, the order of the elements of dst will be reversed. +// For other values of mode Dlatm1 will panic. +// +// If rsign is true and mode is not ±6, each entry of dst will be multiplied by 1 +// or -1 with probability 0.5 +// +// dist specifies the type of distribution to be used when mode == ±6: +// dist == 1: Uniform[0,1) +// dist == 2: Uniform[-1,1) +// dist == 3: Normal(0,1) +// For other values of dist Dlatm1 will panic. +// +// rnd is used as a source of random numbers. +func Dlatm1(dst []float64, mode int, cond float64, rsign bool, dist int, rnd *rand.Rand) { + amode := mode + if amode < 0 { + amode = -amode + } + if amode < 1 || 6 < amode { + panic("testlapack: invalid mode") + } + if cond < 1 { + panic("testlapack: cond < 1") + } + if amode == 6 && (dist < 1 || 3 < dist) { + panic("testlapack: invalid dist") + } + + n := len(dst) + if n == 0 { + return + } + + switch amode { + case 1: + dst[0] = 1 + for i := 1; i < n; i++ { + dst[i] = 1 / cond + } + case 2: + for i := 0; i < n-1; i++ { + dst[i] = 1 + } + dst[n-1] = 1 / cond + case 3: + dst[0] = 1 + if n > 1 { + alpha := math.Pow(cond, -1/float64(n-1)) + for i := 1; i < n; i++ { + dst[i] = math.Pow(alpha, float64(i)) + } + } + case 4: + dst[0] = 1 + if n > 1 { + condInv := 1 / cond + alpha := (1 - condInv) / float64(n-1) + for i := 1; i < n; i++ { + dst[i] = float64(n-i-1)*alpha + condInv + } + } + case 5: + alpha := math.Log(1 / cond) + for i := range dst { + dst[i] = math.Exp(alpha * rnd.Float64()) + } + case 6: + switch dist { + case 1: + for i := range dst { + dst[i] = rnd.Float64() + } + case 2: + for i := range dst { + dst[i] = 2*rnd.Float64() - 1 + } + case 3: + for i := range dst { + dst[i] = rnd.NormFloat64() + } + } + } + + if rsign && amode != 6 { + for i, v := range dst { + if rnd.Float64() < 0.5 { + dst[i] = -v + } + } + } + + if mode < 0 { + for i := 0; i < n/2; i++ { + dst[i], dst[n-i-1] = dst[n-i-1], dst[i] + } + } +}