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

okay bestie, welcome to the Library Functions Manual page for /home/abui...la_geamv.f(3) ✨💖

💖 NAME 💖

This is the manual page for /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dla_geamv.f — yes, the whole path, we’re not hiding it 🫶. The documented routine is DLA_GEAMV.

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

       subroutine DLA_GEAMV (trans, m, n, alpha, a, lda, x, incx, beta, y,
           incy)
           DLA_GEAMV computes a matrix-vector product using a general matrix to
           calculate error bounds.

🎀 Function/Subroutine Documentation 🎀

   subroutine DLA_GEAMV (integer trans, integer m, integer n, double precision
       alpha, double precision, dimension( lda, * ) a, integer lda, double
       precision, dimension( * ) x, integer incx, double precision beta, double
       precision, dimension( * ) y, integer incy)
       DLA_GEAMV computes a matrix-vector product using a general matrix to
       calculate error bounds.

🌸 Purpose 🌸

okay so here’s the vibe: DLA_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 — 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 — INTEGER. On entry, M specifies the number of rows of the matrix A. M must be at least zero. Unchanged on exit.
• N — INTEGER. On entry, N specifies the number of columns of the matrix A. N must be at least zero. Unchanged on exit.
• ALPHA — DOUBLE PRECISION. On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
• A — DOUBLE PRECISION 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 — 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 — DOUBLE PRECISION 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 — INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit.
• BETA — 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 — DOUBLE PRECISION 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 not referenced and the function performs a quick return.
• INCY — INTEGER. On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit.

Also, the source says: Level 2 Blas routine.

👑 Author 👑

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

Definition at line 174 of file dla_geamv.f.

🫶 Author (auto-generated) 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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kisses and sparkles, this page is LAPACK Version 3.12.0 and it lives at /home/abui...la_geamv.f(3) 🎀💖🦋