BLAS/SRC/dsyr.f(3)

💖 BLAS/SRC/dsyr.f 💖

okay bestie, this page is from the Library Functions Manual, and it's all about dsyr from BLAS. It's giving linear algebra main character energy, and we're gonna get through every single detail together. No cap. ✨

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🌸 NAME 🌸

BLAS/SRC/dsyr.f — that's the whole name section, bestie. Short, iconic, zero notes. 👑

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine dsyr (uplo, n, alpha, x, incx, a, lda)
    DSYR

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💅 Function/Subroutine Documentation 💅

subroutine dsyr (character uplo, integer n, double precision alpha, double
       precision, dimension(*) x, integer incx, double precision,
       dimension(lda,*) a, integer lda)
       DSYR

🎀 Purpose 🎀

okay so DSYR performs the symmetric rank 1 operation:

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

where alpha is a real scalar, x is an n element vector and A is an n by n symmetric matrix. That's the whole vibe. 💖

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🦋 Parameters 🦋

• UPLO — is CHARACTER*1. On entry, UPLO specifies whether the upper or lower triangular part of the array A is to be referenced as follows:
  • 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 — is INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero.
• ALPHA — is DOUBLE PRECISION. On entry, ALPHA specifies the scalar alpha.
• 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 — is INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero.
• 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.
• 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 ).

bestie, real talk: N must be at least zero, INCX must not be zero, and LDA must be at least max( 1, n ). Those aren't suggestions, they're the rules. 🚨💅

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👑 Author 👑

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

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🔥 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 131 of file dsyr.f.

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🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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okay bestie, that's the whole page 💖 it's from LAPACK Version 3.12.0, page BLAS/SRC/dsyr.f(3), and the footer only gives us that version and page, so that's the tea I'm passing along. Go slay your symmetric rank 1 update, you absolute icon. ✨🫶👑