SRC/dsytrs2.f(3)

okay bestie, welcome to SRC/dsytrs2.f(3) from the Library Functions Manual — this is the page where LAPACK’s symmetric-solve subroutine gets its main character moment, and it ate. ✨

✨ NAME ✨

SRC/dsytrs2.f — that’s the file/page name, periodt. 💅

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🎀 SYNOPSIS 🎀

🦋 Functions/Subroutines 🦋

subroutine dsytrs2 (uplo, n, nrhs, a, lda, ipiv, b, ldb, work, info)
           DSYTRS2

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🌸 Function/Subroutine Documentation 🌸

💖 subroutine dsytrs2 💖

subroutine dsytrs2 (character uplo, integer n, integer nrhs, double
     precision, dimension( lda, * ) a, integer lda, integer, dimension( * )
     ipiv, double precision, dimension( ldb, * ) b, integer ldb, double
     precision, dimension( * ) work, integer info)
     DSYTRS2

💜 Purpose 💜

okay so DSYTRS2 solves a system of linear equations A*X = B with a real symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF and converted by DSYCONV. slay. ✨

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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*U**T;
• = 'L': lower triangular, form is A = L*D*L**T.

🎀 N 🎀

• N is INTEGER — 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 DOUBLE PRECISION array, dimension (LDA,N) — the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by DSYTRF.

Note that A is input/output. This might be counter-intuitive, and one may think that A is input only. A is input/output. This is because, at the start of the subroutine, we permute A in a form and then we permute A back to its original form at the end. 🙈

⭐ 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 DSYTRF.

🍓 B 🍓

• B is DOUBLE PRECISION array, dimension (LDB,NRHS) — on entry, the right hand side matrix B. On exit, the solution matrix X.

💜 LDB 💜

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

🌸 WORK 🌸

• WORK is DOUBLE PRECISION array, dimension (N).

🔥 INFO 🔥

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

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👑 Author 👑

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

Definition at line 130 of file dsytrs2.f.

🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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and that’s the tea, bestie: this cutie is LAPACK, Version 3.12.0, and the page is SRC/dsytrs2.f(3). mwah 💅✨