BLAS/SRC/dsymv.f(3)

💖 BLAS/SRC/dsymv.f(3) — the LAPACK girlies present: dsymv 💖

okay so bestie, welcome to the BLAS corner of LAPACK. this is the manual page for BLAS/SRC/dsymv.f, and honestly? it's giving workhorse. it's giving "I do one thing and I do it flawlessly." let's get into it 🫶

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✨ NAME ✨

BLAS/SRC/dsymv.f — the file that brings you dsymv, a level 2 BLAS routine. she's symmetric, she's matrix-vector, she's iconic 💅

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🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine dsymv (uplo, n, alpha, a, lda, x, incx, beta, y, incy)

DSYMV

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🦋 Function/Subroutine Documentation 🦋

subroutine dsymv (character uplo, integer n, double precision alpha, double
    precision, dimension(lda,*) a, integer lda, double precision,
    dimension(*) x, integer incx, double precision beta, double precision,
    dimension(*) y, integer incy)

DSYMV

🎀 Purpose

no cap, here's the whole vibe. DSYMV 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. periodt. 💅

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👑 Parameters

• UPLO — UPLO is CHARACTER*1. on entry, UPLO specifies whether the upper or lower triangular part of the array A is to be referenced, like this:
  • UPLO = 'U' or 'u' — only the upper triangular part of A is to be referenced.
  • UPLO = 'L' or 'l' — only the lower triangular part of A is to be referenced.
• N — N is INTEGER. on entry, N specifies the order of the matrix A. N must be at least zero.
• ALPHA — ALPHA is DOUBLE PRECISION. on entry, ALPHA specifies the scalar alpha.
• A — A is DOUBLE PRECISION array, dimension ( LDA, N ). 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. 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. she only reads half of you, and that's on efficiency ✨
• 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 ).
• X — X is DOUBLE PRECISION array, dimension at least ( 1 + ( n - 1 )*abs( INCX ) ). before entry, the incremented array X must contain the n element vector x.
• INCX — INCX is INTEGER. on entry, INCX specifies the increment for the elements of X. INCX must not be zero. 🚨 zero is NOT the move, bestie.
• BETA — BETA is DOUBLE PRECISION. on entry, BETA specifies the scalar beta. when BETA is supplied as zero then Y need not be set on input. free pass, we love to see it 💖
• Y — Y is DOUBLE PRECISION 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. she's a main character who changes on her way out, and honestly? slay.
• INCY — INCY is INTEGER. on entry, INCY specifies the increment for the elements of Y. INCY must not be zero. 🚨 again: not zero. not ever.

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🌈 Author

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

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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.

not me getting emotional over a changelog from 1986 😭 these four literally built the infrastructure we're all standing on. legends only. 👑

Definition at line 151 of file dsymv.f.

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💜 Author

Generated automatically by Doxygen for LAPACK from the source code.

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and that's the whole page, bestie!! 🎀 this one shipped as Version 3.12.0, dated Tue Nov 28 2023 12:08:41, and it lives at BLAS/SRC/dsymv.f(3). go forth and multiply your matrices (symmetric ones only, obviously) 💅✨🦋