BLAS/SRC/sspmv.f(3)

📦
version 3.12.0 · 7 versions
, in centos-stream 10, fedora 43, fedora 44

✨ BLAS/SRC/sspmv.f ✨

okay bestie, so this page lives in the LAPACK manual, in the BLAS/SRC directory, and it's the whole saga of sspmv — a Level 2 BLAS routine that is lowkey doing the most for matrix-vector math 💅

🌸 SYNOPSIS 🌸

Functions/Subroutines

  • subroutine sspmv (uplo, n, alpha, ap, x, incx, beta, y, incy) — SSPMV, the icon itself 👑

💖 Function/Subroutine Documentation 💖

subroutine sspmv (character uplo, integer n, real alpha, real, dimension(*) ap, real, dimension(*) x, integer incx, real beta, real, dimension(*) y, integer incy)

SSPMV 🫶

🦋 Purpose:

no cap, SSPMV 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, supplied in packed form. it's giving efficient storage, it's giving slay ✨

🎀 Parameters

  • UPLO — UPLO is CHARACTER*1. On entry, UPLO specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array AP as follows:
    • UPLO = 'U' or 'u' — The upper triangular part of A is supplied in AP.
    • UPLO = 'L' or 'l' — The lower triangular part of A is supplied in AP.
  • N — N is INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero.
  • ALPHA — ALPHA is REAL. On entry, ALPHA specifies the scalar alpha.
  • 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 part of the symmetric 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 part of the symmetric 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. like, the packing order literally flips depending on which triangle you picked, iykyk 💀
  • 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.
  • INCX — INCX is INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero. 🚨
  • BETA — BETA is REAL. On entry, BETA specifies the scalar beta. When BETA is supplied as zero then Y need not be set on input. cute little shortcut, we love her 🫶
  • 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. main character energy: she goes in as one thing and leaves as another 😭
  • INCY — INCY is INTEGER. On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. 🚨

👑 Author

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

🔥 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.
fr fr, 1986!! these legends were out here writing BLAS before most of us existed and the code is still iconic. we stan 🌈

Definition at line 146 of file sspmv.f.

💜 Author

Generated automatically by Doxygen for LAPACK from the source code.

and that's the whole page bestie!! 🎀 this was Version 3.12.0, generated Tue Nov 28 2023 12:08:41, and it all came straight from BLAS/SRC/sspmv.f(3). go forth and multiply some matrices, but like, symmetrically and in packed form 💖✨🦋

📦 where this page comes from