ZSYSV_ROOK(3)

💖 NAME 💖

Okay bestie, this is ZSYSV_ROOK(3) from the Library Functions Manual — and the NAME entry is literally this file path: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zsysv_rook.f. That's the whole vibe. 💅

✨ SYNOPSIS ✨

🌈 Functions/Subroutines 🌈

subroutine ZSYSV_ROOK (uplo, n, nrhs, a, lda, ipiv, b, ldb, work, lwork,
    info)

Slay, this is the one: ZSYSV_ROOK computes the solution to system of linear equations A * X = B for SY matrices.

🧚 Function/Subroutine Documentation 🧚

subroutine ZSYSV_ROOK (character uplo, integer n, integer nrhs, complex*16,
    dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv,
    complex*16, dimension( ldb, * ) b, integer ldb, complex*16, dimension( *
    ) work, integer lwork, integer info)

ZSYSV_ROOK computes the solution to system of linear equations A * X = B for SY matrices.

🌸 Purpose 🌸

Okay so here's the tea: ZSYSV_ROOK computes the solution to a complex system of linear equations A * X = B, where A is an N-by-N symmetric matrix and X and B are N-by-NRHS matrices. 🫶

The diagonal pivoting method is used to factor A as A = U * D * U**T, if UPLO = 'U', or A = L * D * L**T, if UPLO = 'L', where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and D is symmetric and block diagonal with 1-by-1 and 2-by-2 diagonal blocks. ✨

ZSYTRF_ROOK is called to compute the factorization of a complex symmetric matrix A using the bounded Bunch-Kaufman () diagonal pivoting method. 🔥

The factored form of A is then used to solve the system of equations A * X = B by calling ZSYTRS_ROOK. 💯

🎀 Parameters 🎀

UPLO

UPLO is CHARACTER*1.

• = 'U': upper triangle of A is stored;
• = 'L': lower triangle of A is stored.

N

N is INTEGER. The number of linear equations, i.e., the order of the matrix A. N >= 0. 💜

NRHS

NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. 💜

A

A is COMPLEX*16 array, dimension (LDA,N).

• On entry, the symmetric matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
• On exit, if INFO = 0, the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**T or A = L*D*L**T as computed by ZSYTRF_ROOK.

LDA

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

IPIV

IPIV is INTEGER array, dimension (N). Details of the interchanges and the block structure of D, as determined by ZSYTRF_ROOK.

If UPLO = 'U':

• If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block.
• If IPIV(k) < 0 and IPIV(k-1) < 0, then rows and columns k and -IPIV(k) were interchanged and rows and columns k-1 and -IPIV(k-1) were inerchaged, D(k-1:k,k-1:k) is a 2-by-2 diagonal block.

If UPLO = 'L':

• If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block.
• If IPIV(k) < 0 and IPIV(k+1) < 0, then rows and columns k and -IPIV(k) were interchanged and rows and columns k+1 and -IPIV(k+1) were inerchaged, D(k:k+1,k:k+1) is a 2-by-2 diagonal block.

B

B is COMPLEX*16 array, dimension (LDB,NRHS).

• On entry, the N-by-NRHS right hand side matrix B.
• On exit, if INFO = 0, the N-by-NRHS solution matrix X.

LDB

LDB is INTEGER. The leading dimension of the array B. LDB >= max(1,N). 🦋

WORK

WORK is COMPLEX*16 array, dimension (MAX(1,LWORK)).

• On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

LWORK is INTEGER. The length of WORK. LWORK >= 1, and for best performance LWORK >= max(1,N*NB), where NB is the optimal blocksize for ZSYTRF_ROOK.

TRS will be done with Level 2 BLAS.

If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA. 😭

INFO

INFO is INTEGER.

• = 0: successful exit
• < 0: if INFO = -i, the i-th argument had an illegal value
• > 0: if INFO = i, D(i,i) is exactly zero. The factorization has been completed, but the block diagonal matrix D is exactly singular, so the solution could not be computed. 💀

👑 Author 👑

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

🌟 Contributors: 🌟

• December 2016, Igor Kozachenko, Computer Science Division, University of California, Berkeley
• September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas, School of Mathematics, University of Manchester

Definition at line 202 of file zsysv_rook.f.

🤖 Author 🤖

Generated automatically by Doxygen for LAPACK from the source code.

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Catch you later, bestie — this page is from LAPACK Version 3.12.0, source path /home/abui...sysv_rook.f(3). Periodt. 💅✨