/home/abui...la_geamv.f(3)

📦 version 3.12.0, in opensuse-leap 16.0

💅 NAME

Okay bestie, this page is the manual entry for /home/abui...la_geamv.f(3) from the Library Functions Manual, and the source file it’s hyping up is:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cla_geamv.f

Slay. That’s the whole name vibe. 🎀

✨ SYNOPSIS

Functions/Subroutines

subroutine CLA_GEAMV (trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

CLA_GEAMV computes a matrix-vector product using a general matrix to calculate error bounds. Periodt. 💖

🧚 Function/Subroutine Documentation

Here’s the full signature, exactly as it’s giving:

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

CLA_GEAMV computes a matrix-vector product using a general matrix to calculate error bounds. Iconic behavior, honestly. ✨

Purpose

Bestie, CLA_GEAMV performs one of these matrix-vector operations:

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

where alpha and beta are scalars, x and y are vectors, and A is an m by n matrix.

This function is primarily used in calculating error bounds. To protect against underflow during evaluation, components in the resulting vector are perturbed away from zero by (N+1) times the underflow threshold. To prevent unnecessarily large errors for block-structure embedded in general matrices, zero components are not perturbed. A zero entry is considered if all multiplications involved in computing that entry have at least one zero multiplicand.

Parameters

TRANS

TRANS is INTEGER.

On entry, TRANS specifies the operation to be performed as follows:

BLAS_NO_TRANS      y := alpha*abs(A)*abs(x) + beta*abs(y)
BLAS_TRANS         y := alpha*abs(A**T)*abs(x) + beta*abs(y)
BLAS_CONJ_TRANS    y := alpha*abs(A**T)*abs(x) + beta*abs(y)

Unchanged on exit.

M

M is INTEGER.

On entry, M specifies the number of rows of the matrix A. M must be at least zero. Unchanged on exit. 🫶

N

N is INTEGER.

On entry, N specifies the number of columns of the matrix A. N must be at least zero. Unchanged on exit. 🌸

ALPHA

ALPHA is REAL.

On entry, ALPHA specifies the scalar alpha. Unchanged on exit.

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. Unchanged on exit. 💜

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 ). Unchanged on exit.

X

X is COMPLEX array, dimension

( 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. Unchanged on exit. 🦋

INCX

INCX is INTEGER.

On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit.

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. Unchanged on exit.

Y

Y is REAL array, dimension

( 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 not referenced and the function performs a quick return. No cap, that quick return is lowkey convenient. 😭

INCY

INCY is INTEGER.

On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit.

Level 2 Blas routine. 🔥

Author

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

Definition at line 175 of file cla_geamv.f.

👑 Author

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