| // 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" |
| ) |
| |
| // Dgetrs solves a system of equations using an LU factorization. |
| // The system of equations solved is |
| // A * X = B if trans == blas.Trans |
| // A^T * X = B if trans == blas.NoTrans |
| // A is a general n×n matrix with stride lda. B is a general matrix of size n×nrhs. |
| // |
| // On entry b contains the elements of the matrix B. On exit, b contains the |
| // elements of X, the solution to the system of equations. |
| // |
| // a and ipiv contain the LU factorization of A and the permutation indices as |
| // computed by Dgetrf. ipiv is zero-indexed. |
| func (impl Implementation) Dgetrs(trans blas.Transpose, n, nrhs int, a []float64, lda int, ipiv []int, b []float64, ldb int) { |
| checkMatrix(n, n, a, lda) |
| checkMatrix(n, nrhs, b, ldb) |
| if len(ipiv) < n { |
| panic(badIpiv) |
| } |
| if n == 0 || nrhs == 0 { |
| return |
| } |
| if trans != blas.Trans && trans != blas.NoTrans { |
| panic(badTrans) |
| } |
| bi := blas64.Implementation() |
| if trans == blas.NoTrans { |
| // Solve A * X = B. |
| impl.Dlaswp(nrhs, b, ldb, 0, n-1, ipiv, 1) |
| // Solve L * X = B, updating b. |
| bi.Dtrsm(blas.Left, blas.Lower, blas.NoTrans, blas.Unit, |
| n, nrhs, 1, a, lda, b, ldb) |
| // Solve U * X = B, updating b. |
| bi.Dtrsm(blas.Left, blas.Upper, blas.NoTrans, blas.NonUnit, |
| n, nrhs, 1, a, lda, b, ldb) |
| return |
| } |
| // Solve A^T * X = B. |
| // Solve U^T * X = B, updating b. |
| bi.Dtrsm(blas.Left, blas.Upper, blas.Trans, blas.NonUnit, |
| n, nrhs, 1, a, lda, b, ldb) |
| // Solve L^T * X = B, updating b. |
| bi.Dtrsm(blas.Left, blas.Lower, blas.Trans, blas.Unit, |
| n, nrhs, 1, a, lda, b, ldb) |
| impl.Dlaswp(nrhs, b, ldb, 0, n-1, ipiv, -1) |
| } |