| // 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 ( |
| "gonum.org/v1/gonum/blas" |
| "gonum.org/v1/gonum/blas/blas64" |
| ) |
| |
| // Dtrtri computes the inverse of a triangular matrix, storing the result in place |
| // into a. This is the BLAS level 3 version of the algorithm which builds upon |
| // Dtrti2 to operate on matrix blocks instead of only individual columns. |
| // |
| // Dtrtri will not perform the inversion if the matrix is singular, and returns |
| // a boolean indicating whether the inversion was successful. |
| func (impl Implementation) Dtrtri(uplo blas.Uplo, diag blas.Diag, n int, a []float64, lda int) (ok bool) { |
| checkMatrix(n, n, a, lda) |
| if uplo != blas.Upper && uplo != blas.Lower { |
| panic(badUplo) |
| } |
| if diag != blas.NonUnit && diag != blas.Unit { |
| panic(badDiag) |
| } |
| if n == 0 { |
| return false |
| } |
| nonUnit := diag == blas.NonUnit |
| if nonUnit { |
| for i := 0; i < n; i++ { |
| if a[i*lda+i] == 0 { |
| return false |
| } |
| } |
| } |
| |
| bi := blas64.Implementation() |
| |
| nb := impl.Ilaenv(1, "DTRTRI", "UD", n, -1, -1, -1) |
| if nb <= 1 || nb > n { |
| impl.Dtrti2(uplo, diag, n, a, lda) |
| return true |
| } |
| if uplo == blas.Upper { |
| for j := 0; j < n; j += nb { |
| jb := min(nb, n-j) |
| bi.Dtrmm(blas.Left, blas.Upper, blas.NoTrans, diag, j, jb, 1, a, lda, a[j:], lda) |
| bi.Dtrsm(blas.Right, blas.Upper, blas.NoTrans, diag, j, jb, -1, a[j*lda+j:], lda, a[j:], lda) |
| impl.Dtrti2(blas.Upper, diag, jb, a[j*lda+j:], lda) |
| } |
| return true |
| } |
| nn := ((n - 1) / nb) * nb |
| for j := nn; j >= 0; j -= nb { |
| jb := min(nb, n-j) |
| if j+jb <= n-1 { |
| bi.Dtrmm(blas.Left, blas.Lower, blas.NoTrans, diag, n-j-jb, jb, 1, a[(j+jb)*lda+j+jb:], lda, a[(j+jb)*lda+j:], lda) |
| bi.Dtrsm(blas.Right, blas.Lower, blas.NoTrans, diag, n-j-jb, jb, -1, a[j*lda+j:], lda, a[(j+jb)*lda+j:], lda) |
| } |
| impl.Dtrti2(blas.Lower, diag, jb, a[j*lda+j:], lda) |
| } |
| return true |
| } |