BLAS/SRC/dsyr2.f(3)

💖 NAME 💖

BLAS/SRC/dsyr2.f — that’s the name, bestie. The whole name. No extra lore. 💅

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✨ SYNOPSIS ✨

💫 Functions/Subroutines 💫

       subroutine dsyr2 (uplo, n, alpha, x, incx, y, incy, a, lda)
           DSYR2

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🫶 Function/Subroutine Documentation 🫶

okay so the actual signature in all its glory is literally this:

   subroutine dsyr2 (character uplo, integer n, double precision alpha, double
       precision, dimension(*) x, integer incx, double precision, dimension(*)
       y, integer incy, double precision, dimension(lda,*) a, integer lda)
       DSYR2

🎯 Purpose: 🎯

The original source wraps this in Doxygen !> comment markers, but the actual vibe is: DSYR2 performs the symmetric rank 2 operation

   A := alpha*x*y**T + alpha*y*x**T + A,

where alpha is a scalar, x and y are n element vectors, and A is an n by n symmetric matrix. That’s it. That’s the whole little math serve. ✨

🌸 Parameters 🌸

UPLO

UPLO is CHARACTER*1. On entry, UPLO specifies whether the upper or lower triangular part of the array A is to be referenced, like this:

• UPLO = 'U' or 'u' — only the upper triangular part of A is to be referenced.
• UPLO = 'L' or 'l' — only the lower triangular part of A is to be referenced.

N

N is INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero. Zero is allowed, bestie — it’s not a typo. 💛

ALPHA

ALPHA is DOUBLE PRECISION. On entry, ALPHA specifies the scalar alpha.

X

X is DOUBLE PRECISION array, dimension at least

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

Before entry, the incremented array X must contain the n element vector x.

INCX

INCX is INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero.

🚨 Not zero, okay? Not even a little zero. 🚨

Y

Y is DOUBLE PRECISION array, dimension at least

( 1 + ( n - 1 )*abs( INCY ) ).

Before entry, the incremented array Y must contain the n element vector y.

INCY

INCY is INTEGER. On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.

🚨 Same rule, babes: INCY cannot be zero either. 🚨

A

A is DOUBLE PRECISION array, dimension ( LDA, N ).

Before entry with UPLO = 'U' or 'u', the leading n by n upper triangular part of the array A must contain the upper triangular part of the symmetric matrix, and the strictly lower triangular part of A is not referenced. On exit, the upper triangular part of the array A is overwritten by the upper triangular part of the updated matrix.

Before entry with UPLO = 'L' or 'l', the leading n by n lower triangular part of the array A must contain the lower triangular part of the symmetric matrix, and the strictly upper triangular part of A is not referenced. On exit, the lower triangular part of the array A is overwritten by the lower triangular part of the updated matrix.

It’s giving “only touch the triangle you were assigned” energy, and honestly? Respect. 🫶

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 ).

👑 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.

Definition at line 146 of file dsyr2.f.

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💅 Author 💅

Generated automatically by Doxygen for LAPACK from the source code.

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okay that’s the whole page, bestie — signed off by LAPACK Version 3.12.0 for BLAS/SRC/dsyr2.f(3). No date listed in the footer, so we’re not inventing one — just precision, vibes, and a symmetric rank 2 moment. 💖✨🎀