BLAS/SRC/stpsv.f(3)

✨ BLAS/SRC/stpsv.f — the tea on stpsv ✨

okay bestie, welcome to the LAPACK corner of the group chat, this one lives in BLAS/SRC/stpsv.f and it's lowkey a whole legend 👑

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🌸 NAME 🌸

BLAS/SRC/stpsv.f — no cap, that's the whole name, she's mysterious like that 💅

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🦋 SYNOPSIS 🦋

Functions/Subroutines

• subroutine stpsv (uplo, trans, diag, n, ap, x, incx) — aka STPSV, our main character 🎀

Function/Subroutine Documentation

subroutine stpsv (character uplo, character trans, character diag, integer n, real, dimension(*) ap, real, dimension(*) x, integer incx)

STPSV ✨ (yes she's shouting her own name, iconic behaviour, we stan)

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💖 PURPOSE 💖

okay so real talk, STPSV solves one of these systems of equations:

A*x = b,   or   A**T*x = b,

where b and x are n element vectors and A is an n by n unit or non-unit, upper or lower triangular matrix, supplied in packed form 🫶

⚠️ bestie listen. There is no test for singularity or near-singularity in this routine. None. Zero. She simply does not check. Such tests must be performed before calling this routine. This is the "I'm not your mom, check your own matrix" energy and honestly? respect 🙈

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🌈 PARAMETERS 🌈

• UPLO — UPLO is CHARACTER*1. On entry, UPLO tells us whether the matrix is upper or lower triangular, like this:
  • UPLO = 'U' or 'u' → A is an upper triangular matrix.
  • UPLO = 'L' or 'l' → A is a lower triangular matrix.
• TRANS — TRANS is CHARACTER*1. On entry, TRANS says which equations we're solving, fr fr:
  • TRANS = 'N' or 'n' → A*x = b.
  • TRANS = 'T' or 't' → A**T*x = b.
  • TRANS = 'C' or 'c' → A**T*x = b.
• DIAG — DIAG is CHARACTER*1. On entry, DIAG says whether or not A is unit triangular:
  • DIAG = 'U' or 'u' → A is assumed to be unit triangular.
  • DIAG = 'N' or 'n' → A is not assumed to be unit triangular.
• N — N is INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero. (so like, zero is fine, negative is not, don't even try it 💀)
• AP — AP is REAL array, dimension at least ( ( n*( n + 1 ) )/2 ).
  • Before entry with UPLO = 'U' or 'u', the array AP must contain the upper triangular matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 ) respectively, and so on.
  • Before entry with UPLO = 'L' or 'l', the array AP must contain the lower triangular matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respectively, and so on.
  • Note that when DIAG = 'U' or 'u', the diagonal elements of A are not referenced, but are assumed to be unity ✨
• X — X is REAL array, dimension at least ( 1 + ( n - 1 )*abs( INCX ) ).
  • Before entry, the incremented array X must contain the n element right-hand side vector b. On exit, X is overwritten with the solution vector x. she really said "new X who dis" 💅
• INCX — INCX is INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero. periodt. 🚫

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👑 AUTHOR 👑

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

the whole squad showed up for this one, no cap 🫶

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🧚 FURTHER DETAILS 🧚

• Level 2 Blas routine. ⭐
• -- Written on 22-October-1986.
  • Jack Dongarra, Argonne National Lab.
  • Jeremy Du Croz, Nag Central Office.
  • Sven Hammarling, Nag Central Office.
  • Richard Hanson, Sandia National Labs.

ngl the fact that this baddie has been serving since 1986 is giving timeless, ageless, mother energy. 22-October-1986!! she's been slaying for decades 💜

• Definition at line 143 of file stpsv.f. 📍

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💫 AUTHOR (the meta one) 💫

Generated automatically by Doxygen for LAPACK from the source code. she was born from code, raised by docs, and she ate 🌸

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okay that's the whole page bestie, every flag, every packed column, every author, all of it 🎀

Version 3.12.0 — Tue Nov 28 2023 12:08:41 — BLAS/SRC/stpsv.f(3) 💖

bye ily, go check your matrices for singularity before you call her, she will NOT do it for you 😭✨🦋