BLAS/SRC/ssymv.f(3)

💅 BLAS/SRC/ssymv.f — the ssymv glow-up

okay so bestie, welcome to the manual page for BLAS/SRC/ssymv.f, and honestly? she's a legend. this is the single-precision symmetric matrix-vector girlie, and she absolutely ate. let's get into it ✨

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✨ SYNOPSIS ✨

🌸 Functions/Subroutines

• subroutine ssymv (uplo, n, alpha, a, lda, x, incx, beta, y, incy) — the one and only SSYMV, no cap 🫶

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🎀 Function/Subroutine Documentation 🎀

subroutine ssymv (character uplo, integer n, real alpha, real,
    dimension(lda,*) a, integer lda, real, dimension(*) x, integer incx,
    real beta, real, dimension(*) y, integer incy)

SSYMV — main character energy, literally 💅

🦋 Purpose:

!>
!> SSYMV  performs the matrix-vector  operation
!>
!>    y := alpha*A*x + beta*y,
!>
!> where alpha and beta are scalars, x and y are n element vectors and
!> A is an n by n symmetric matrix.
!>

so basically she does the classic y := alpha*A*x + beta*y thing — alpha and beta are just scalars, x and y are n-element vectors, and A is an n by n symmetric matrix. iconic behavior tbh 🔥

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💖 Parameters 💖

• UPLO

UPLO is CHARACTER*1 — on entry, UPLO tells her which triangular part of the array A she should be looking at, like this:

• UPLO = 'U' or 'u' → only the upper triangular part of A is referenced, periodt.
• UPLO = 'L' or 'l' → only the lower triangular part of A is referenced, and that's that 🌸

• N

N is INTEGER — on entry, N specifies the order of the matrix A. and lowkey the one rule: N must be at least zero. do not come in here with a negative N bestie 😭

• ALPHA

ALPHA is REAL — on entry, ALPHA specifies the scalar alpha. that's it, that's the whole vibe ✨

• A

A is REAL array, dimension ( LDA, N ) — okay so listen:

• Before entry with UPLO = 'U' or 'u', the leading n by n upper triangular part of the array A must contain the upper triangular part of the symmetric matrix, and the strictly lower triangular part of A is not referenced. she's not even looking at it 💀
• Before entry with UPLO = 'L' or 'l', the leading n by n lower triangular part of the array A must contain the lower triangular part of the symmetric matrix, and the strictly upper triangular part of A is not referenced. same energy, flipped 🦋

• LDA

LDA is INTEGER — on entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA must be at least max( 1, n ). no exceptions, bestie 🫶

• X

X is REAL array, dimension at least ( 1 + ( n - 1 )*abs( INCX ) ) — before entry, the incremented array X must contain the n element vector x. give her the goods 💖

• INCX

INCX is INTEGER — on entry, INCX specifies the increment for the elements of X. INCX must not be zero. like, at all. ever. 🙈

• BETA

BETA is REAL — on entry, BETA specifies the scalar beta. and here's a cute little shortcut: when BETA is supplied as zero then Y need not be set on input. you're welcome 😌

• Y

Y is REAL array, dimension at least ( 1 + ( n - 1 )*abs( INCY ) ) — before entry, the incremented array Y must contain the n element vector y. On exit, Y is overwritten by the updated vector y. so yeah, she's destructive in the fun way — your old y is gone, replaced by the new one 🌈

• INCY

INCY is INTEGER — on entry, INCY specifies the increment for the elements of Y. INCY must not be zero. same rule as INCX, fr fr 🍓

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👑 Author 👑

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

the whole squad, honestly. legends only 🧚

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⭐ Further Details: ⭐

!>
!>  Level 2 Blas routine.
!>  The vector and matrix arguments are not referenced when N = 0, or M = 0
!>
!>  -- 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.
!>

• she's a Level 2 Blas routine, iykyk 💜
• the vector and matrix arguments are not referenced when N = 0, or M = 0 — so no touching, no reading, nothing. she's not nosy 💀
• written on 22-October-1986 by Jack Dongarra (Argonne National Lab.), Jeremy Du Croz (Nag Central Office.), Sven Hammarling (Nag Central Office.), and Richard Hanson (Sandia National Labs.) — actual vintage icons, we stan 🌸

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Definition at line 151 of file ssymv.f.

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🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code. (yes bestie, a robot wrote this bit, not me 💅)

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and that's the whole page! 🎀 LAPACK, Version 3.12.0 — documented for BLAS/SRC/ssymv.f(3), mwah, go forth and multiply your symmetric matrices 🦋💖✨