SRC/dsptrs.f(3)

💜 SRC/dsptrs.f — the whole vibe

okay so this is the manpage for SRC/dsptrs.f, bestie. it's a Fortran file, it lives in LAPACK, and it's lowkey a legend. come learn with me 💅

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine dsptrs (uplo, n, nrhs, ap, ipiv, b, ldb, info)

that's DSPTRS 🎀 (yes the header of the function block literally just says DSPTRS and honestly? iconic of it)

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🦋 Function/Subroutine Documentation 🦋

subroutine dsptrs (character uplo, integer n, integer nrhs, double
    precision, dimension( * ) ap, integer, dimension( * ) ipiv, double
    precision, dimension( ldb, * ) b, integer ldb, integer info)

DSPTRS 🌸

🎯 Purpose 🎯

!>
!> DSPTRS solves a system of linear equations A*X = B with a real
!> symmetric matrix A stored in packed format using the factorization
!> A = U*D*U**T or A = L*D*L**T computed by DSPTRF.
!>

so fr fr what it does: it solves A*X = B. A is a real symmetric matrix, and it's stored in packed format 📦 (no wasted space, we love a minimalist queen). it uses the factorization A = U*D*U**T or A = L*D*L**T that DSPTRF already computed for you. no cap, that's the whole job 🫶

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🌈 Parameters 🌈

• UPLO — UPLO is CHARACTER*1. tells us whether the factorization details 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. and babes, N >= 0 — that's the rule ✨
• NRHS — NRHS is INTEGER. the number of right hand sides, i.e. the number of columns of the matrix B. NRHS >= 0 💖
• AP — AP is DOUBLE PRECISION array, dimension (N*(N+1)/2). the block diagonal matrix D plus the multipliers used to obtain the factor U or L as computed by DSPTRF, stored as a packed triangular matrix. so much info in so little space, she's efficient 🔥
• IPIV — IPIV is INTEGER array, dimension (N). the details of the interchanges and the block structure of D as determined by DSPTRF. receipts, basically 💅
• B — B is DOUBLE PRECISION array, dimension (LDB,NRHS). on entry, the right hand side matrix B. on exit, the solution matrix X. she goes in one girl and comes out a whole different girl 😭✨
• LDB — LDB is INTEGER. the leading dimension of the array B. and LDB >= max(1,N) — do not test her on this one 🫶
• INFO — INFO is INTEGER:
  • = 0: successful exit 🎉 slay
  • < 0: if INFO = -i, the i-th argument had an illegal value 🙈 (so like, check your args bestie)

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👑 Author 👑

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

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📌 Definition at line 114 of file dsptrs.f.

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⭐ Author (the meta one) ⭐

Generated automatically by Doxygen for LAPACK from the source code. (not a human, just vibes and a perl script 🧚)

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and that's the page!! thanks for coming to my ted talk 🍓 stay packed, stay factored 💜

— with love, from LAPACK, Version 3.12.0, dated SRC/dsptrs.f(3) 💖🎀🦋