SRC/spptrs.f(3)

🦋 SRC/spptrs.f(3) — Library Functions Manual

okay so this is the manual page for SRC/spptrs.f(3), living its best life in the Library Functions Manual. Buckle up, bestie, we're doing Fortran linear algebra and we're gonna be so normal about it. This page ate and left no crumbs. 💅✨

🎀 NAME 🎀

SRC/spptrs.f

That's the name. Short, iconic, no cap. 🫶

✨ SYNOPSIS ✨

🧚 Functions/Subroutines

• subroutine spptrs (uplo, n, nrhs, ap, b, ldb, info) — the one and only entry point, labeled SPPTRS. Slay. 💖

💅 Function/Subroutine Documentation 💅

🌟 subroutine spptrs

subroutine spptrs (character uplo, integer n, integer nrhs, real, dimension( * ) ap, real, dimension( ldb, * ) b, integer ldb, integer info)

SPPTRS — yes bestie, same name, she's consistent. 👑

🎯 Purpose:

SPPTRS solves a system of linear equations A*X = B with a symmetric positive definite matrix A in packed storage using the Cholesky factorization A = U**T*U or A = L*L**T computed by SPPTRF. That's the whole purpose, and ngl, it's giving math main character energy. 🔥

🌸 Parameters

• UPLO — is CHARACTER*1. Value 'U': upper triangle of A is stored; value 'L': lower triangle of A is stored.
• N — is INTEGER. The order of the matrix A. N >= 0.
• NRHS — is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
• AP — is REAL array, dimension (N*(N+1)/2). The triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, packed columnwise in a linear array. The j-th column of U or L is stored in the array AP as follows:

if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j;
if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n.

Not me being obsessed with packed-columnwise storage realness, iykyk. 🍓

• B — is REAL array, dimension (LDB,NRHS). On entry, the right hand side matrix B. On exit, the solution matrix X. Literally a glow-up from RHS to solution. 💖
• LDB — is INTEGER. The leading dimension of the array B. LDB >= max(1,N). Lowkey important, don't skip the vibe check. 🌈
• INFO — is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. Highkey the built-in vibe check: zero is slay, negative means something was not it. 💀

👑 Author

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

Definition at line 107 of file spptrs.f.

💖 AUTHOR

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cute sign-off: this page is from LAPACK Version 3.12.0, source SRC/spptrs.f(3). The footer doesn't give a date, so I'm not inventing one — we respect the source, periodt. Byeee, bestie 🫶✨