DTRTRS(3)

💅 DTRTRS(3) — LAPACK's triangular solve, bestie

okay so bestie, welcome to the DTRTRS(3) page from the Library Functions Manual for LAPACK. the header is being extra and calls the file /home/abui...RC/dtrtrs.f(3), but we're here for the tea, not the header drama. 🫶

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✨ NAME ✨

the NAME section is literally just the source path, and it's giving "I am the file":

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

🌸 SYNOPSIS 🌸

Functions/Subroutines

one subroutine, one moment, one slay:

subroutine DTRTRS (uplo, trans, diag, n, nrhs, a, lda, b, ldb, info)
    DTRTRS

💖 Function/Subroutine Documentation 💖

here's the full signature, character for character, no cap:

subroutine DTRTRS (character uplo, character trans, character diag, integer
    n, integer nrhs, double precision, dimension( lda, * ) a, integer lda,
    double precision, dimension( ldb, * ) b, integer ldb, integer info)
    DTRTRS

🎀 Purpose 🎀

so DTRTRS solves a triangular system of the form:

A * X = B  or  A**T * X = B,

where A is a triangular matrix of order N, and B is an N-by-NRHS matrix. A check is made to verify that A is nonsingular. like yes, we love a safety check, bestie 💅

💅 Parameters 💅

UPLO

UPLO is CHARACTER*1, and the vibe is:

= 'U':  A is upper triangular;
= 'L':  A is lower triangular.

TRANS

TRANS is CHARACTER*1. it specifies the form of the system of equations:

= 'N':  A * X = B  (No transpose)
= 'T':  A**T * X = B  (Transpose)
= 'C':  A**H * X = B  (Conjugate transpose = Transpose)

DIAG

DIAG is CHARACTER*1:

= 'N':  A is non-unit triangular;
= 'U':  A is unit triangular.

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 triangular matrix A. if UPLO = 'U', the leading N-by-N upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. if UPLO = 'L', the leading N-by-N lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. if DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1. iconic behavior, honestly.

LDA

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

B

B is DOUBLE PRECISION array, dimension (LDB,NRHS). on entry, the right hand side matrix B. on exit, if INFO = 0, the solution matrix X.

LDB

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

INFO

INFO is INTEGER:

= 0:  successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the i-th diagonal element of A is zero,
     indicating that the matrix is singular and the solutions
     X have not been computed.

if INFO > 0, that's the singular-matrix warning, and the solutions X have not been computed — no pretending otherwise, bestie. 💀

👑 Author 👑

the contributors behind this one are:

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

Definition at line 138 of file dtrtrs.f.

🤖 Author 🤖

Generated automatically by Doxygen for LAPACK from the source code.

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xoxo, your LAPACK bestie 💖 — footer tea: LAPACK Version 3.12.0, /home/abui...RC/dtrtrs.f(3). mwah! 🎀