| // 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" |
| ) |
| |
| // Dpotrf computes the Cholesky decomposition of the symmetric positive definite |
| // matrix a. If ul == blas.Upper, then a is stored as an upper-triangular matrix, |
| // and a = U^T U is stored in place into a. If ul == blas.Lower, then a = L L^T |
| // is computed and stored in-place into a. If a is not positive definite, false |
| // is returned. This is the blocked version of the algorithm. |
| func (impl Implementation) Dpotrf(ul blas.Uplo, n int, a []float64, lda int) (ok bool) { |
| if ul != blas.Upper && ul != blas.Lower { |
| panic(badUplo) |
| } |
| checkMatrix(n, n, a, lda) |
| |
| if n == 0 { |
| return true |
| } |
| |
| nb := impl.Ilaenv(1, "DPOTRF", string(ul), n, -1, -1, -1) |
| if nb <= 1 || n <= nb { |
| return impl.Dpotf2(ul, n, a, lda) |
| } |
| bi := blas64.Implementation() |
| if ul == blas.Upper { |
| for j := 0; j < n; j += nb { |
| jb := min(nb, n-j) |
| bi.Dsyrk(blas.Upper, blas.Trans, jb, j, |
| -1, a[j:], lda, |
| 1, a[j*lda+j:], lda) |
| ok = impl.Dpotf2(blas.Upper, jb, a[j*lda+j:], lda) |
| if !ok { |
| return ok |
| } |
| if j+jb < n { |
| bi.Dgemm(blas.Trans, blas.NoTrans, jb, n-j-jb, j, |
| -1, a[j:], lda, a[j+jb:], lda, |
| 1, a[j*lda+j+jb:], lda) |
| bi.Dtrsm(blas.Left, blas.Upper, blas.Trans, blas.NonUnit, jb, n-j-jb, |
| 1, a[j*lda+j:], lda, |
| a[j*lda+j+jb:], lda) |
| } |
| } |
| return true |
| } |
| for j := 0; j < n; j += nb { |
| jb := min(nb, n-j) |
| bi.Dsyrk(blas.Lower, blas.NoTrans, jb, j, |
| -1, a[j*lda:], lda, |
| 1, a[j*lda+j:], lda) |
| ok := impl.Dpotf2(blas.Lower, jb, a[j*lda+j:], lda) |
| if !ok { |
| return ok |
| } |
| if j+jb < n { |
| bi.Dgemm(blas.NoTrans, blas.Trans, n-j-jb, jb, j, |
| -1, a[(j+jb)*lda:], lda, a[j*lda:], lda, |
| 1, a[(j+jb)*lda+j:], lda) |
| bi.Dtrsm(blas.Right, blas.Lower, blas.Trans, blas.NonUnit, n-j-jb, jb, |
| 1, a[j*lda+j:], lda, |
| a[(j+jb)*lda+j:], lda) |
| } |
| } |
| return true |
| } |