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[bytom/vapor.git] / vendor / gonum.org / v1 / gonum / lapack / gonum / dlanst.go

diff --git a/vendor/gonum.org/v1/gonum/lapack/gonum/dlanst.go b/vendor/gonum.org/v1/gonum/lapack/gonum/dlanst.go
new file mode 100644 (file)
index 0000000..74eafeb
--- /dev/null
+++ b/vendor/gonum.org/v1/gonum/lapack/gonum/dlanst.go
@@ -0,0 +1,68 @@
+// Copyright ©2016 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 gonum
+
+import (
+       "math"
+
+       "gonum.org/v1/gonum/lapack"
+)
+
+// Dlanst computes the specified norm of a symmetric tridiagonal matrix A.
+// The diagonal elements of A are stored in d and the off-diagonal elements
+// are stored in e.
+func (impl Implementation) Dlanst(norm lapack.MatrixNorm, n int, d, e []float64) float64 {
+       if len(d) < n {
+               panic(badD)
+       }
+       if len(e) < n-1 {
+               panic(badE)
+       }
+       if n <= 0 {
+               return 0
+       }
+       switch norm {
+       default:
+               panic(badNorm)
+       case lapack.MaxAbs:
+               anorm := math.Abs(d[n-1])
+               for i := 0; i < n-1; i++ {
+                       sum := math.Abs(d[i])
+                       if anorm < sum || math.IsNaN(sum) {
+                               anorm = sum
+                       }
+                       sum = math.Abs(e[i])
+                       if anorm < sum || math.IsNaN(sum) {
+                               anorm = sum
+                       }
+               }
+               return anorm
+       case lapack.MaxColumnSum, lapack.MaxRowSum:
+               if n == 1 {
+                       return math.Abs(d[0])
+               }
+               anorm := math.Abs(d[0]) + math.Abs(e[0])
+               sum := math.Abs(e[n-2]) + math.Abs(d[n-1])
+               if anorm < sum || math.IsNaN(sum) {
+                       anorm = sum
+               }
+               for i := 1; i < n-1; i++ {
+                       sum := math.Abs(d[i]) + math.Abs(e[i]) + math.Abs(e[i-1])
+                       if anorm < sum || math.IsNaN(sum) {
+                               anorm = sum
+                       }
+               }
+               return anorm
+       case lapack.NormFrob:
+               var scale float64
+               sum := 1.0
+               if n > 1 {
+                       scale, sum = impl.Dlassq(n-1, e, 1, scale, sum)
+                       sum = 2 * sum
+               }
+               scale, sum = impl.Dlassq(n, d, 1, scale, sum)
+               return scale * math.Sqrt(sum)
+       }
+}