package/gonum
1
0
Fork 0
mirror of https://github.com/gonum/gonum.git synced 2025-10-06 23:52:47 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

lapack/gonum: clean up implementation comments in Dpbtf2

Browse Source
This commit is contained in:
Vladimir Chalupecky
2019-05-27 16:18:18 +02:00
committed by Vladimír Chalupecký
parent 3db45405ae
commit 47d77d149e
1 changed files with 10 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
lapack/gonum/dpbtf2.go
View File

@@ -47,9 +47,9 @@ import (
// version. // version.
// //
// Dpbtf2 is an internal routine, exported for testing purposes. // Dpbtf2 is an internal routine, exported for testing purposes.
func (Implementation) Dpbtf2(ul blas.Uplo, n, kd int, ab []float64, ldab int) (ok bool) { func (Implementation) Dpbtf2(uplo blas.Uplo, n, kd int, ab []float64, ldab int) (ok bool) {
switch { switch {
case ul != blas.Upper && ul != blas.Lower: case uplo != blas.Upper && uplo != blas.Lower:
panic(badUplo) panic(badUplo)
case n < 0: case n < 0:
panic(nLT0) panic(nLT0)
@@ -59,6 +59,7 @@ func (Implementation) Dpbtf2(ul blas.Uplo, n, kd int, ab []float64, ldab int) (o
panic(badLdA) panic(badLdA)
} }
// Quick return if possible.
if n == 0 { if n == 0 {
return return
} }
@@ -70,16 +71,17 @@ func (Implementation) Dpbtf2(ul blas.Uplo, n, kd int, ab []float64, ldab int) (o
bi := blas64.Implementation() bi := blas64.Implementation()
kld := max(1, ldab-1) kld := max(1, ldab-1)
if ul == blas.Upper { if uplo == blas.Upper {
// Compute the Cholesky factorization A = U^T * U.
for j := 0; j < n; j++ { for j := 0; j < n; j++ {
// Compute U(J,J) and test for non positive-definiteness. // Compute U(j,j) and test for non-positive-definiteness.
ajj := ab[j*ldab] ajj := ab[j*ldab]
if ajj <= 0 { if ajj <= 0 {
return false return false
} }
ajj = math.Sqrt(ajj) ajj = math.Sqrt(ajj)
ab[j*ldab] = ajj ab[j*ldab] = ajj
// Compute elements j+1:j+kn of row J and update the trailing submatrix // Compute elements j+1:j+kn of row j and update the trailing submatrix
// within the band. // within the band.
kn := min(kd, n-j-1) kn := min(kd, n-j-1)
if kn > 0 { if kn > 0 {
@@ -89,16 +91,16 @@ func (Implementation) Dpbtf2(ul blas.Uplo, n, kd int, ab []float64, ldab int) (o
} }
return true return true
} }
// Compute the Cholesky factorization A = L * L^T.
for j := 0; j < n; j++ { for j := 0; j < n; j++ {
// Compute L(J,J) and test for non positive-definiteness. // Compute L(j,j) and test for non-positive-definiteness.
ajj := ab[j*ldab+kd] ajj := ab[j*ldab+kd]
if ajj <= 0 { if ajj <= 0 {
return false return false
} }
ajj = math.Sqrt(ajj) ajj = math.Sqrt(ajj)
ab[j*ldab+kd] = ajj ab[j*ldab+kd] = ajj
// Compute elements j+1:j+kn of column j and update the trailing submatrix
// Compute elements J+1:J+KN of column J and update the trailing submatrix
// within the band. // within the band.
kn := min(kd, n-j-1) kn := min(kd, n-j-1)
if kn > 0 { if kn > 0 {