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

✨ NAME ✨

This is the Library Functions Manual page for /home/abui...la_syamv.f(3), bestie. The source file it's documenting is /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zla_syamv.f 💖.

🌸 SYNOPSIS 🌸

💅 Functions/Subroutines 💅

• subroutine ZLA_SYAMV (uplo, n, alpha, a, lda, x, incx, beta, y, incy) — ZLA_SYAMV computes a matrix-vector product using a symmetric indefinite matrix to calculate error bounds. 🫶

👑 Function/Subroutine Documentation 👑

💖 subroutine ZLA_SYAMV 💖

subroutine ZLA_SYAMV (integer uplo, integer n, double precision alpha, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( * ) x, integer incx, double precision beta, double precision, dimension( * ) y, integer incy)

ZLA_SYAMV computes a matrix-vector product using a symmetric indefinite matrix to calculate error bounds. That's the whole assignment, no cap 🔥.

🎯 Purpose 🎯

Okay so the source comments are literally serving this exact energy:

!>
!> ZLA_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.
!>
!> 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.
!>

So yeah: y := alpha*abs(A)*abs(x) + beta*abs(y), with underflow protection and a whole little rule about zero entries. Iconic 💅.

🧚 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 — Only the upper triangular part of A is to be referenced.
  • UPLO = BLAS_LOWER — 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 DOUBLE PRECISION . On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
• A — A is COMPLEX*16 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*16 array, dimension at least ( 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 DOUBLE PRECISION . 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 DOUBLE PRECISION 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.

🌈 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 177 of file zla_syamv.f. 📍

🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code. 💅

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Cute sign-off time: this page is from LAPACK, Version 3.12.0, and it lives at /home/abui...la_syamv.f(3). The footer didn't include a date, bestie — that's the whole footer. Mwah! 💖