BLAS/SRC/cher2k.f(3)

💖 BLAS/SRC/cher2k.f(3) 💖 — Library Functions Manual, bestie

okay so we are literally in the BLAS trenches and this page is the manual for cher2k, a Level 3 BLAS routine. Group-chat voice on, details stay exactly where they belong. 💅

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🌸 NAME 🌸

BLAS/SRC/cher2k.f — that's the name, that's the file, no cap. It's the CHER2K BLAS routine page. 🫶

✨ SYNOPSIS ✨

Here's the function list, short and sweet:

📚 Functions/Subroutines 📚

• subroutine cher2k (uplo, trans, n, k, alpha, a, lda, b, ldb, beta, c, ldc) — CHER2K

🫶 Function/Subroutine Documentation 🫶

🌈 CHER2K 🌈

subroutine cher2k (character uplo, character trans, integer n, integer k,
    complex alpha, complex, dimension(lda,*) a, integer lda, complex,
    dimension(ldb,*) b, integer ldb, real beta, complex, dimension(ldc,*) c,
    integer ldc)

🎯 Purpose 🎯

CHER2K performs one of the hermitian rank 2k operations — yes, hermitian, rank 2k, say it with your chest. 💖

C := alpha*A*B**H + conjg( alpha )*B*A**H + beta*C,

or

C := alpha*A**H*B + conjg( alpha )*B**H*A + beta*C,

where alpha and beta are scalars with beta real, C is an n by n hermitian matrix, and A and B are n by k matrices in the first case and k by n matrices in the second case. 🦋

🧚 Parameters 🧚

Okay bestie, here's every parameter, no skipping:

• UPLO — CHARACTER*1. On entry, UPLO specifies whether the upper or lower triangular part of the array C is to be referenced, like this:
  • UPLO = 'U' or 'u' — only the upper triangular part of C is to be referenced.
  • UPLO = 'L' or 'l' — only the lower triangular part of C is to be referenced.
• TRANS — CHARACTER*1. On entry, TRANS specifies the operation to be performed, and it's giving choose-your-own-adventure:
  • TRANS = 'N' or 'n' — C := alpha*A*B**H + conjg( alpha )*B*A**H + beta*C.
  • TRANS = 'C' or 'c' — C := alpha*A**H*B + conjg( alpha )*B**H*A + beta*C.
• N — INTEGER. On entry, N specifies the order of the matrix C. N must be at least zero. Periodt.
• K — INTEGER. On entry with TRANS = 'N' or 'n', K specifies the number of columns of the matrices A and B, and on entry with TRANS = 'C' or 'c', K specifies the number of rows of the matrices A and B. K must be at least zero.
• ALPHA — COMPLEX. On entry, ALPHA specifies the scalar alpha.
• A — COMPLEX array, dimension ( LDA, ka ), where ka is k when TRANS = 'N' or 'n', and is n otherwise. Before entry with TRANS = 'N' or 'n', the leading n by k part of the array A must contain the matrix A, otherwise the leading k by n part of the array A must contain the matrix A.
• LDA — INTEGER. On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. When TRANS = 'N' or 'n' then LDA must be at least max( 1, n ), otherwise LDA must be at least max( 1, k ).
• B — COMPLEX array, dimension ( LDB, kb ), where kb is k when TRANS = 'N' or 'n', and is n otherwise. Before entry with TRANS = 'N' or 'n', the leading n by k part of the array B must contain the matrix B, otherwise the leading k by n part of the array B must contain the matrix B.
• LDB — INTEGER. On entry, LDB specifies the first dimension of B as declared in the calling (sub) program. When TRANS = 'N' or 'n' then LDB must be at least max( 1, n ), otherwise LDB must be at least max( 1, k ).
• BETA — REAL. On entry, BETA specifies the scalar beta.
• C — COMPLEX array, dimension ( LDC, N ). Okay bestie, this one has layers:
  • Before entry with UPLO = 'U' or 'u', the leading n by n upper triangular part of the array C must contain the upper triangular part of the hermitian matrix, and the strictly lower triangular part of C is not referenced. On exit, the upper triangular part of the array C 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 C must contain the lower triangular part of the hermitian matrix, and the strictly upper triangular part of C is not referenced. On exit, the lower triangular part of the array C is overwritten by the lower triangular part of the updated matrix.
  • Note that the imaginary parts of the diagonal elements need not be set, they are assumed to be zero, and on exit they are set to zero. 👀
• LDC — INTEGER. On entry, LDC specifies the first dimension of C as declared in the calling (sub) program. LDC must be at least max( 1, n ).

👑 Author 👑

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

🔥 Further Details 🔥

Receipts, bestie:

• Level 3 Blas routine.
• Written on 8-February-1989.
  • Jack Dongarra, Argonne National Laboratory.
  • Iain Duff, AERE Harwell.
  • Jeremy Du Croz, Numerical Algorithms Group Ltd.
  • Sven Hammarling, Numerical Algorithms Group Ltd.
• Modified 8-Nov-93 to set C(J,J) to REAL( C(J,J) ) when BETA = 1.
  • Ed Anderson, Cray Research Inc.

📍 Definition 📍

Definition at line 196 of file cher2k.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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okay that's the whole tea, bestie. This page is from LAPACK — Version 3.12.0 — and the footer tag on the original is BLAS/SRC/cher2k.f(3). Stay hermitian, stay hydrated, and don't forget beta is real. 💖✨💅