SRC/zsytrs_rook.f(3)

🌸 SRC/zsytrs_rook.f(3) 🌸

okay so this is a page from the Library Functions Manual and bestie, it is so specific — it's literally one subroutine and its whole entire vibe. let's get into it 💅

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✨ NAME ✨

SRC/zsytrs_rook.f — that's the file, that's the name, no cap 🎀

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✨ SYNOPSIS ✨

🦋 Functions/Subroutines

• subroutine zsytrs_rook (uplo, n, nrhs, a, lda, ipiv, b, ldb, info) — the one and only, ZSYTRS_ROOK 👑

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✨ Function/Subroutine Documentation ✨

💖 the subroutine itself

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

ZSYTRS_ROOK — say it with me, main character energy ⭐

🧚 Purpose:

ZSYTRS_ROOK solves a system of linear equations A*X = B with a complex symmetric matrix A using the factorization A = U*D*UT or A = L*D*LT computed by ZSYTRF_ROOK.

so like, you already did the hard part with ZSYTRF_ROOK, and now this lil icon finishes the job 😌✨

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🌸 Parameters

UPLO

UPLO is CHARACTER*1 Specifies whether the details of the factorization are stored as an upper or lower triangular matrix. = 'U': Upper triangular, form is A = U*D*UT; = 'L': Lower triangular, form is A = L*D*LT.

bestie you gotta tell it which triangle you're living in — upper girlie or lower girlie, pick one 💅

N

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

the size of the whole situation. and yes, N >= 0, respect the boundary 🫶

NRHS

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

how many right hand sides you're serving — literally the column count of B. also NRHS >= 0 fr fr 🌈

A

A is COMPLEX*16 array, dimension (LDA,N) The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by ZSYTRF_ROOK.

this is the stuff ZSYTRF_ROOK handed you — the block diagonal matrix D plus the multipliers that got you U or L. don't mess with it, it's already iconic 👑

LDA

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

the leading dimension of A. LDA >= max(1,N), no exceptions 🎀

IPIV

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

all the interchange deets and the block structure of D, straight from ZSYTRF_ROOK. iykyk 🦋

B

B is COMPLEX*16 array, dimension (LDB,NRHS) On entry, the right hand side matrix B. On exit, the solution matrix X.

the glow-up of the century honestly: goes in as the right hand side matrix B, comes out as the solution matrix X. we love a transformation ✨😭

LDB

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

leading dimension of B. LDB >= max(1,N) — same energy as LDA, keep it consistent 💜

INFO

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

the vibe check at the end 💀 0 means slay, you're done. if it's < 0 and INFO = -i, then the i-th argument had an illegal value — so like, go check your arguments bestie 🙈

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🎀 Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

shoutout to the whole squad, periodt 🫶

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🌟 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

legends, all of them 👑✨

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📍 Definition at line 134 of file zsytrs_rook.f.

that's where it lives, that's the address, go visit 🏠

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💫 Author (the meta one) 💫

Generated automatically by Doxygen for LAPACK from the source code. yeah, a robot wrote the page about the subroutine. it's giving inception 🌀

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lowkey the whole thing is just: factor once with ZSYTRF_ROOK, then let this little icon solve A*X = B for you. slay. 💖

LAPACK, Version 3.12.0 — okay bye bestie, mwah, go solve something symmetric 💋🌸🦋