blob: 24e98ddd5edf2cd0f49daac2347c189c239c2f82 [file] [log] [blame]
 // Copyright ©2018 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" ) // Dlauu2 computes the product // U * Uᵀ if uplo is blas.Upper // Lᵀ * L if uplo is blas.Lower // where U or L is stored in the upper or lower triangular part of A. // Only the upper or lower triangle of the result is stored, overwriting // the corresponding factor in A. func (impl Implementation) Dlauu2(uplo blas.Uplo, n int, a []float64, lda int) { switch { case uplo != blas.Upper && uplo != blas.Lower: panic(badUplo) case n < 0: panic(nLT0) case lda < max(1, n): panic(badLdA) } // Quick return if possible. if n == 0 { return } if len(a) < (n-1)*lda+n { panic(shortA) } bi := blas64.Implementation() if uplo == blas.Upper { // Compute the product U*Uᵀ. for i := 0; i < n; i++ { aii := a[i*lda+i] if i < n-1 { a[i*lda+i] = bi.Ddot(n-i, a[i*lda+i:], 1, a[i*lda+i:], 1) bi.Dgemv(blas.NoTrans, i, n-i-1, 1, a[i+1:], lda, a[i*lda+i+1:], 1, aii, a[i:], lda) } else { bi.Dscal(i+1, aii, a[i:], lda) } } } else { // Compute the product Lᵀ*L. for i := 0; i < n; i++ { aii := a[i*lda+i] if i < n-1 { a[i*lda+i] = bi.Ddot(n-i, a[i*lda+i:], lda, a[i*lda+i:], lda) bi.Dgemv(blas.Trans, n-i-1, i, 1, a[(i+1)*lda:], lda, a[(i+1)*lda+i:], lda, aii, a[i*lda:], 1) } else { bi.Dscal(i+1, aii, a[i*lda:], 1) } } } }