SRC/cla_heamv.f(3)

💅 SRC/cla_heamv.f(3) — Library Functions Manual 💅

Okay bestie, welcome to the SRC/cla_heamv.f(3) page from the Library Functions Manual. We're talking about cla_heamv, and I'm highkey obsessed with how it computes a matrix-vector product using a Hermitian indefinite matrix to calculate error bounds. Iconic, no cap.

✨ NAME ✨

SRC/cla_heamv.f

That's the name, periodt.

🦋 SYNOPSIS 🦋

Functions/Subroutines

subroutine cla_heamv (uplo, n, alpha, a, lda, x, incx, beta, y, incy)

CLA_HEAMV computes a matrix-vector product using a Hermitian indefinite matrix to calculate error bounds. Slay.

🌸 Function/Subroutine Documentation 🌸

subroutine cla_heamv (integer uplo, integer n, real alpha, complex,
    dimension( lda, * ) a, integer lda, complex, dimension( * ) x, integer
    incx, real beta, real, dimension( * ) y, integer incy)

CLA_HEAMV computes a matrix-vector product using a Hermitian indefinite matrix to calculate error bounds.

🎀 Purpose: 🎀

The source's Purpose block literally says CLA_SYAMV performs the matrix-vector operation:

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

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

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. That's the whole rule, bestie.

🧚 Parameters 🧚

• UPLO — UPLO is INTEGER. On entry, UPLO specifies whether the upper or lower triangular part of the array A is to be referenced as follows: UPLO = BLAS_UPPER means only the upper triangular part of A is to be referenced; UPLO = BLAS_LOWER means only the lower triangular part of A is to be referenced. 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, n ). Unchanged on exit.
• X — X is COMPLEX array, dimension ( 1 + ( n - 1 )*abs( INCX ) ). 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 + ( n - 1 )*abs( INCY ) ). 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.
• INCY — INCY is INTEGER. On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit.

No cap: INCX and INCY must not be zero. That's a hard no, bestie.

🌟 Author 🌟

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

🔥 Further Details: 🔥

• 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.
• -- Modified for the absolute-value product, April 2006
  • Jason Riedy, UC Berkeley

Definition at line 176 of file cla_heamv.f.

💖 Author 💖

Generated automatically by Doxygen for LAPACK from the source code.

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Okay, that's the whole page! Shoutout to LAPACK Version 3.12.0 and the source SRC/cla_heamv.f(3) — that's the footer, fr fr. No extra date in the footer, so I'm not inventing one. Bye bestie! 💅✨