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

diff --git a/vendor/gonum.org/v1/gonum/lapack/gonum/dlange.go b/vendor/gonum.org/v1/gonum/lapack/gonum/dlange.go
new file mode 100644 (file)
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+++ b/vendor/gonum.org/v1/gonum/lapack/gonum/dlange.go
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+// Copyright ©2015 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"
+)
+
+// Dlange computes the matrix norm of the general m×n matrix a. The input norm
+// specifies the norm computed.
+//  lapack.MaxAbs: the maximum absolute value of an element.
+//  lapack.MaxColumnSum: the maximum column sum of the absolute values of the entries.
+//  lapack.MaxRowSum: the maximum row sum of the absolute values of the entries.
+//  lapack.NormFrob: the square root of the sum of the squares of the entries.
+// If norm == lapack.MaxColumnSum, work must be of length n, and this function will panic otherwise.
+// There are no restrictions on work for the other matrix norms.
+func (impl Implementation) Dlange(norm lapack.MatrixNorm, m, n int, a []float64, lda int, work []float64) float64 {
+       // TODO(btracey): These should probably be refactored to use BLAS calls.
+       checkMatrix(m, n, a, lda)
+       switch norm {
+       case lapack.MaxRowSum, lapack.MaxColumnSum, lapack.NormFrob, lapack.MaxAbs:
+       default:
+               panic(badNorm)
+       }
+       if norm == lapack.MaxColumnSum && len(work) < n {
+               panic(badWork)
+       }
+       if m == 0 && n == 0 {
+               return 0
+       }
+       if norm == lapack.MaxAbs {
+               var value float64
+               for i := 0; i < m; i++ {
+                       for j := 0; j < n; j++ {
+                               value = math.Max(value, math.Abs(a[i*lda+j]))
+                       }
+               }
+               return value
+       }
+       if norm == lapack.MaxColumnSum {
+               if len(work) < n {
+                       panic(badWork)
+               }
+               for i := 0; i < n; i++ {
+                       work[i] = 0
+               }
+               for i := 0; i < m; i++ {
+                       for j := 0; j < n; j++ {
+                               work[j] += math.Abs(a[i*lda+j])
+                       }
+               }
+               var value float64
+               for i := 0; i < n; i++ {
+                       value = math.Max(value, work[i])
+               }
+               return value
+       }
+       if norm == lapack.MaxRowSum {
+               var value float64
+               for i := 0; i < m; i++ {
+                       var sum float64
+                       for j := 0; j < n; j++ {
+                               sum += math.Abs(a[i*lda+j])
+                       }
+                       value = math.Max(value, sum)
+               }
+               return value
+       }
+       if norm == lapack.NormFrob {
+               var value float64
+               scale := 0.0
+               sum := 1.0
+               for i := 0; i < m; i++ {
+                       scale, sum = impl.Dlassq(n, a[i*lda:], 1, scale, sum)
+               }
+               value = scale * math.Sqrt(sum)
+               return value
+       }
+       panic("lapack: bad matrix norm")
+}