SSYCONVF(3)

SSYCONVF(3) 💅

okay so bestie, welcome to the Library Functions Manual entry for SSYCONVF — yes, it's giving LAPACK subroutine energy, and we're gonna get through every single detail together. 🫶

NAME 🎀

The NAME section is literally just this file path, no cap:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/ssyconvf.f

SYNOPSIS ✨

Functions/Subroutines

subroutine SSYCONVF (uplo, way, n, a, lda, e, ipiv, info)
    SSYCONVF

Function/Subroutine Documentation 🦋

Here's the full signature, copied exactly because we do not play with code:

subroutine SSYCONVF (character uplo, character way, integer n, real,
    dimension( lda, * ) a, integer lda, real, dimension( * ) e, integer,
    dimension( * ) ipiv, integer info)
    SSYCONVF

Purpose 🌸

If parameter WAY = 'C': SSYCONVF converts the factorization output format used in SSYTRF, provided on entry in parameter A, into the factorization output format used in SSYTRF_RK (or SSYTRF_BK) that is stored on exit in parameters A and E. It also converts in place details of the interchanges stored in IPIV from the format used in SSYTRF into the format used in SSYTRF_RK (or SSYTRF_BK). 💅

If parameter WAY = 'R': SSYCONVF performs the conversion in reverse direction, i.e. it converts the factorization output format used in SSYTRF_RK (or SSYTRF_BK), provided on entry in parameters A and E, into the factorization output format used in SSYTRF that is stored on exit in parameter A. It also converts in place details of the interchanges stored in IPIV from the format used in SSYTRF_RK (or SSYTRF_BK) into the format used in SSYTRF. ✨

Parameters 🎀

UPLO

UPLO is CHARACTER*1. It specifies whether the details of the factorization are stored as an upper or lower triangular matrix A.

• 'U': Upper triangular
• 'L': Lower triangular

WAY

WAY is CHARACTER*1.

• 'C': Convert
• 'R': Revert

N

N is INTEGER. The order of the matrix A. N >= 0.

A

A is REAL array, dimension (LDA,N).

1) If WAY ='C':

• On entry, contains factorization details in format used in SSYTRF:
  • a) all elements of the symmetric block diagonal matrix D on the diagonal of A and on superdiagonal (or subdiagonal) of A, and
  • b) If UPLO = 'U': multipliers used to obtain factor U in the superdiagonal part of A. If UPLO = 'L': multipliers used to obtain factor L in the superdiagonal part of A.
• On exit, contains factorization details in format used in SSYTRF_RK or SSYTRF_BK:
  • a) ONLY diagonal elements of the symmetric block diagonal matrix D on the diagonal of A, i.e. D(k,k) = A(k,k); (superdiagonal (or subdiagonal) elements of D are stored on exit in array E), and
  • b) If UPLO = 'U': factor U in the superdiagonal part of A. If UPLO = 'L': factor L in the subdiagonal part of A.

2) If WAY ='R':

• On entry, contains factorization details in format used in SSYTRF_RK or SSYTRF_BK:
  • a) ONLY diagonal elements of the symmetric block diagonal matrix D on the diagonal of A, i.e. D(k,k) = A(k,k); (superdiagonal (or subdiagonal) elements of D are stored on exit in array E), and
  • b) If UPLO = 'U': factor U in the superdiagonal part of A. If UPLO = 'L': factor L in the subdiagonal part of A.
• On exit, contains factorization details in format used in SSYTRF:
  • a) all elements of the symmetric block diagonal matrix D on the diagonal of A and on superdiagonal (or subdiagonal) of A, and
  • b) If UPLO = 'U': multipliers used to obtain factor U in the superdiagonal part of A. If UPLO = 'L': multipliers used to obtain factor L in the superdiagonal part of A.

LDA

LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N).

E

E is REAL array, dimension (N).

1) If WAY ='C':

• On entry, just a workspace.
• On exit, contains the superdiagonal (or subdiagonal) elements of the symmetric block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks, where:
  • If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
  • If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

2) If WAY ='R':

• On entry, contains the superdiagonal (or subdiagonal) elements of the symmetric block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks, where:
  • If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) not referenced;
  • If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) not referenced.
• On exit, is not changed.

IPIV

IPIV is INTEGER array, dimension (N).

1) If WAY ='C':

• On entry, details of the interchanges and the block structure of D in the format used in SSYTRF.
• On exit, details of the interchanges and the block structure of D in the format used in SSYTRF_RK (or SSYTRF_BK).

1) If WAY ='R':

• On entry, details of the interchanges and the block structure of D in the format used in SSYTRF_RK (or SSYTRF_BK).
• On exit, details of the interchanges and the block structure of D in the format used in SSYTRF.

INFO

INFO is INTEGER.

• = 0: successful exit
• < 0: if INFO = -i, the i-th argument had an illegal value

Author 🫶

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Contributors: 🧚

November 2017, Igor Kozachenko, Computer Science Division, University of California, Berkeley

Definition at line 205 of file ssyconvf.f.

Author (Doxygen note) 🤖

Generated automatically by Doxygen for LAPACK from the source code.

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