BLAS/SRC/chpmv.f(3)

🫶 BLAS/SRC/chpmv.f — Library Functions Manual 🫶

okay so bestie, welcome to the Library Functions Manual page for BLAS/SRC/chpmv.f. This is the chpmv subroutine’s moment, and yes, it’s giving Level-2 BLAS main character energy. Let’s get into it 💅✨

🌸 NAME 🌸

BLAS/SRC/chpmv.f — literally the file, and it’s serving the chpmv subroutine. Iconic.

✨ SYNOPSIS ✨

Functions/Subroutines

• subroutine chpmv (uplo, n, alpha, ap, x, incx, beta, y, incy) — CHPMV

💖 Function/Subroutine Documentation 💖

Here’s the full signature, copied exactly because we do not play with source code around here:

subroutine chpmv (character uplo, integer n, complex alpha, complex,
       dimension(*) ap, complex, dimension(*) x, integer incx, complex beta,
       complex, dimension(*) y, integer incy)
       CHPMV

So yeah — CHPMV. That’s the routine, that’s the vibe 🫶

Purpose

CHPMV 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 hermitian matrix, supplied in packed form. Periodt 💫

Parameters

• 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 — is INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero. No negative-order nonsense, bestie 🚫
• ALPHA — is COMPLEX. On entry, ALPHA specifies the scalar alpha.
• AP — is COMPLEX 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 hermitian 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 hermitian 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 the imaginary parts of the diagonal elements need not be set and are assumed to be zero. Very demure, very packed-matrix 💐
• X — is COMPLEX array, dimension at least ( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented array X must contain the n element vector x.
• INCX — is INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero.

bestie, fr fr: INCX must not be zero. That’s the rule.

• BETA — is COMPLEX. On entry, BETA specifies the scalar beta. When BETA is supplied as zero then Y need not be set on input.
• Y — is COMPLEX 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.
• INCY — is INTEGER. On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.

and yes, INCY must not be zero either. We stay consistent 💅

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.

Definition at line 148 of file chpmv.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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okay bestie, that’s the whole page. Sign-off flex: LAPACK Version 3.12.0, source BLAS/SRC/chpmv.f(3) — mwah 💋✨