BLAS/SRC/cgemv.f(3)

💅 NAME 💅

BLAS/SRC/cgemv.f — bestie, this is the file, and the star of the show inside it is CGEMV 🎀

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✨ SYNOPSIS ✨

Functions/Subroutines

• subroutine cgemv (trans, m, n, alpha, a, lda, x, incx, beta, y, incy) — CGEMV 💖

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🦋 Function/Subroutine Documentation 🦋

🌸 The signature, in all its glory 🌸

subroutine cgemv (character trans, integer m, integer n, complex alpha,
    complex, dimension(lda,*) a, integer lda, complex, dimension(*) x,
    integer incx, complex beta, complex, dimension(*) y, integer incy)

CGEMV 🔥

🎯 Purpose

okay so listen 🫶 — CGEMV performs one of these matrix-vector operations:

y := alpha*A*x + beta*y,   or   y := alpha*A**T*x + beta*y,   or

y := alpha*A**H*x + beta*y,

where alpha and beta are scalars, x and y are vectors and A is an m by n matrix. That's the whole vibe 💫

🌈 Parameters

⭐ TRANS

TRANS is CHARACTER*1

On entry, TRANS tells you which operation is getting performed, like:

• TRANS = 'N' or 'n' → y := alpha*A*x + beta*y.
• TRANS = 'T' or 't' → y := alpha*A**T*x + beta*y.
• TRANS = 'C' or 'c' → y := alpha*A**H*x + beta*y.

⭐ M

M is INTEGER

On entry, M specifies the number of rows of the matrix A. M must be at least zero. (yes, zero is allowed, we love a lowkey degenerate case 🍓)

⭐ N

N is INTEGER

On entry, N specifies the number of columns of the matrix A. N must be at least zero too 💜

⭐ ALPHA

ALPHA is COMPLEX

On entry, ALPHA specifies the scalar alpha. Just a lil scalar, no big deal ✨

⭐ A

A is COMPLEX array, dimension ( LDA, N )

Before entry, the leading m by n part of the array A must contain the matrix of coefficients. That's the main character right there 👑

⭐ 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, m ). no cap, it's a hard requirement 🚨

⭐ X

X is COMPLEX array, dimension at least

• ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n'
• and at least ( 1 + ( m - 1 )*abs( INCX ) ) otherwise.

Before entry, the incremented array X must contain the vector x. bestie please size this right, I'm begging 🙈

⭐ INCX

INCX is INTEGER

On entry, INCX specifies the increment for the elements of X. INCX must not be zero. 💀 (fr fr, do not pass zero)

⭐ BETA

BETA is COMPLEX

On entry, BETA specifies the scalar beta. When BETA is supplied as zero then Y need not be set on input — little treat for you 🎁

⭐ Y

Y is COMPLEX array, dimension at least

• ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n'
• and at least ( 1 + ( n - 1 )*abs( INCY ) ) otherwise.

Before entry with BETA non-zero, the incremented array Y must contain the vector y. On exit, Y is overwritten by the updated vector y. 💫

If either m or n is zero, then Y is not referenced and the function performs a quick return. iconic, it just leaves 🧚

⭐ INCY

INCY is INTEGER

On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. same energy as INCX, don't test me 😭

👑 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.

And the origin story, we stan a documented lineage 🫶:

-- 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 159 of file cgemv.f. 📍

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🌟 Author 🌟

Generated automatically by Doxygen for LAPACK from the source code. (not a human, just a bot doing its lil job 🤖✨)

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aaaand that's the page, bestie — LAPACK, Version 3.12.0, BLAS/SRC/cgemv.f(3). go forth and multiply your matrices 💖🌸🦋💅