BLAS/SRC/cgeru.f(3)

✨ NAME ✨

BLAS/SRC/cgeru.f — that's the file, bestie. It's the BLAS source page you landed on, straight out of the Library Functions Manual, and it's all about one lil' subroutine that's about to eat 💅

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🎀 SYNOPSIS 🎀

Functions/Subroutines

• subroutine cgeru (m, n, alpha, x, incx, y, incy, a, lda) — CGERU. That's the whole squad right there: m, n, alpha, x, incx, y, incy, a, lda. No cap.

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🌸 Function/Subroutine Documentation 🌸

Here's the full signature, character-for-character, because we do not freestyle with declarations:

subroutine cgeru (integer m, integer n, complex alpha, complex, dimension(*)
    x, integer incx, complex, dimension(*) y, integer incy, complex,
    dimension(lda,*) a, integer lda)

CGERU 👑

💖 Purpose 💖

Okay so, straight from the source, here's what CGERU actually does:

!>
!> CGERU  performs the rank 1 operation
!>
!>    A := alpha*x*y**T + A,
!>
!> where alpha is a scalar, x is an m element vector, y is an n element
!> vector and A is an m by n matrix.
!>

It's giving rank 1 operation, and honestly? Iconic. You hand it a scalar alpha, an m-element vector x, and an n-element vector y, and it folds alpha*x*y**T right on top of your m-by-n matrix A. Main character energy fr fr 🔥

🌈 Parameters 🌈

M

M is INTEGER. On entry, M specifies the number of rows of the matrix A. M must be at least zero — so like, zero rows is fine, negative rows is not it 🙈

N

N is INTEGER. On entry, N specifies the number of columns of the matrix A. N must be at least zero. Same vibe check as M ✨

ALPHA

ALPHA is COMPLEX. On entry, ALPHA specifies the scalar alpha. That's the whole job. She's just a scalar and she knows it 💅

X

X is COMPLEX array, dimension at least

( 1 + ( m - 1 )*abs( INCX ) ).

Before entry, the incremented array X must contain the m element vector x. So make sure X is actually loaded up before you come at her with it 🫶

INCX

INCX is INTEGER. On entry, INCX specifies the increment for the elements of X. And listen — INCX must not be zero. Like, that's the one rule. Don't do it 💀

Y

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. Yes you need Y and X. It's a whole two-vector situation, we love that for us 🌸

INCY

INCY is INTEGER. On entry, INCY specifies the increment for the elements of Y. Same deal as INCX: INCY must not be zero. Periodt 🎀

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. On exit, A is overwritten by the updated matrix. So she does get rewritten — that's not a bug, that's the assignment, bestie 😭🔥

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 ).

Read that carefully. max( 1, m ). Not m. Not n. Lock it in 👑

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👑 Author 👑

Credit where credit is due, and there's a whole committee:

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

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💜 Further Details 💜

The receipts, verbatim:

!>
!>  Level 2 Blas routine.
!>
!>  -- 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.
!>

Level 2 BLAS routine, written on 22-October-1986 — literally older than your mom and still out here slaying on every call 🧚✨

Also worth knowing: it's defined at line 129 of file cgeru.f. That's the actual line, not a vibe.

Author of this page itself: generated automatically by Doxygen for LAPACK from the source code. Not a human, but she ate anyway 🤖💖

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That's the whole page, bestie — every parameter, every dimension expression, every "must not be zero", all of it preserved and none of it skipped. Go forth and call cgeru responsibly. 🦋

Signing off from LAPACK, Version 3.12.0, on page BLAS/SRC/cgeru.f(3) — see you in the next manpage, mwah 🫶💅