TESTING/LIN/dtrt01.f(3)

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version 3.12.1 · 3 versions
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💅 NAME 💅

Okay bestie, this is the manual page for TESTING/LIN/dtrt01.f(3) from the Library Functions Manual — and the whole page is about TESTING/LIN/dtrt01.f. Lowkey iconic.

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine dtrt01 (uplo, diag, n, a, lda, ainv, ldainv, rcond, work,
    resid)

DTRT01 — that's the subroutine, no cap.

🦋 Function/Subroutine Documentation 🦋

Signature

subroutine dtrt01 (character uplo, character diag, integer n, double
    precision, dimension( lda, * ) a, integer lda, double precision,
    dimension( ldainv, * ) ainv, integer ldainv, double precision rcond,
    double precision, dimension( * ) work, double precision resid)

DTRT01

Purpose

DTRT01 computes the residual for a triangular matrix A times its inverse:

RESID = norm( A*AINV - I ) / ( N * norm(A) * norm(AINV) * EPS ),

where EPS is the machine epsilon. Periodt.

Parameters

  • UPLO — CHARACTER*1. Specifies whether the matrix A is upper or lower triangular. = 'U': upper triangular. = 'L': lower triangular.
  • DIAG — CHARACTER*1. Specifies whether or not the matrix A is unit triangular. = 'N': non-unit triangular. = 'U': unit triangular.
  • N — INTEGER. The order of the matrix A. N >= 0.
  • A — DOUBLE PRECISION array, dimension (LDA,N). The triangular matrix A. If UPLO = 'U', the leading n by n upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n by n lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1.
  • LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
  • AINV — DOUBLE PRECISION array, dimension (LDAINV,N). On entry, the (triangular) inverse of the matrix A, in the same storage format as A. On exit, the contents of AINV are destroyed. 💀 So don't expect your input to survive, bestie.
  • LDAINV — INTEGER. The leading dimension of the array AINV. LDAINV >= max(1,N).
  • RCOND — DOUBLE PRECISION. The reciprocal condition number of A, computed as 1/(norm(A) * norm(AINV)).
  • WORK — DOUBLE PRECISION array, dimension (N).
  • RESID — DOUBLE PRECISION. norm(A*AINV - I) / ( N * norm(A) * norm(AINV) * EPS ).

Author

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

Definition at line 122 of file dtrt01.f.

🌈 Author 🌈

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