BLAS/SRC/ssyr2.f(3)

🎀 NAME

BLAS/SRC/ssyr2.f — okay so this is the BLAS/SRC/ssyr2.f(3) page from the Library Functions Manual, and it's literally all about the ssyr2 BLAS routine. 💅

---

✨ SYNOPSIS

🧚 Functions/Subroutines

• subroutine ssyr2 (uplo, n, alpha, x, incx, y, incy, a, lda) — SSYR2

---

💖 Function/Subroutine Documentation

Here's the full signature, bestie, no cap:

subroutine ssyr2 (character uplo, integer n, real alpha, real, dimension(*) x, integer incx, real, dimension(*) y, integer incy, real, dimension(lda,*) a, integer lda)

SSYR2

🦋 Purpose

okay so the whole point of SSYR2 is that it 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. periodt. 🫶

💅 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 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 — 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.

🚨 bestie, INCX must not be zero. that's a hard no. 💀

• 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.

🚨 and same energy for INCY: it must not be zero. fr fr. 🙈

• A — A is REAL 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 — 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 ssyr2.f.

🌈 Author

Generated automatically by Doxygen for LAPACK from the source code.

---

💖 that's the whole manual page, bestie — footer vibes are LAPACK Version 3.12.0, page BLAS/SRC/ssyr2.f(3). byeeee 🫶✨