BLAS/SRC/sspr2.f(3)

✨ NAME ✨

okay so bestie, this is the page for BLAS/SRC/sspr2.f from the Library Functions Manual — it's literally all about the sspr2 subroutine, and the vibe is very “BLAS says hi, pay attention.” 💅

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🦋 SYNOPSIS 🦋

🌸 Functions/Subroutines 🌸

• subroutine sspr2 (uplo, n, alpha, x, incx, y, incy, ap) — the main character: SSPR2.

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💅 Function/Subroutine Documentation 💅

subroutine sspr2 (character uplo, integer n, real alpha, real, dimension(*)
     x, integer incx, real, dimension(*) y, integer incy, real, dimension(*)
     ap)

SSPR2 — yes, this is the icon, the moment, the subroutine. ✨

🎯 Purpose 🎯

okay so SSPR2 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, supplied in packed form. no cap, that's the whole point. 💖

🌈 Parameters 🌈

• UPLO — UPLO is CHARACTER*1. On entry, UPLO specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array AP as follows:
  • UPLO = 'U' or 'u' — The upper triangular part of A is supplied in AP.
  • UPLO = 'L' or 'l' — The lower triangular part of A is supplied in AP.
• N — N is INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero.
• ALPHA — ALPHA is REAL. On entry, ALPHA specifies the scalar alpha.
• X — X is REAL 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.
• Y — Y is REAL 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.
• AP — AP is REAL array, dimension at least ( ( n*( n + 1 ) )/2 ).
  • Before entry with UPLO = 'U' or 'u', the array AP must contain the upper triangular part of the symmetric matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 ) respectively, and so on. On exit, the array AP is overwritten by the upper triangular part of the updated matrix.
  • Before entry with UPLO = 'L' or 'l', the array AP must contain the lower triangular part of the symmetric matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respectively, and so on. On exit, the array AP is overwritten by the lower triangular part of the updated matrix.

👑 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 141 of file sspr2.f.

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💜 Author 💜

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