SRC/stpcon.f(3)

✨ NAME ✨

SRC/stpcon.f — that’s the page name, bestie, and it’s living in the Library Functions Manual 💅

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✨ SYNOPSIS ✨

Functions/Subroutines 🫶

• subroutine stpcon (norm, uplo, diag, n, ap, rcond, work, iwork, info) — STPCON

subroutine stpcon (norm, uplo, diag, n, ap, rcond, work, iwork, info)

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✨ Function/Subroutine Documentation ✨

subroutine stpcon (character norm, character uplo, character diag, integer
n, real, dimension( * ) ap, real rcond, real, dimension( * ) work,
integer, dimension( * ) iwork, integer info)

STPCON ✨

✨ Purpose ✨

Okay so STPCON estimates the reciprocal of the condition number of a packed triangular matrix A, in either the 1-norm or the infinity-norm — no cap 🧚

The norm of A is computed and an estimate is obtained for norm(inv(A)), then the reciprocal of the condition number is computed as:

RCOND = 1 / ( norm(A) * norm(inv(A)) ).

✨ Parameters ✨

• NORM — CHARACTER*1 — tells us whether the 1-norm condition number or the infinity-norm condition number is required:
  • = '1' or 'O': 1-norm;
  • = 'I': Infinity-norm.
• UPLO — CHARACTER*1 — which triangle of A we’re working with:
  • = 'U': A is upper triangular;
  • = 'L': A is lower triangular.
• DIAG — CHARACTER*1 — unit or non-unit diagonal vibe check:
  • = 'N': A is non-unit triangular;
  • = 'U': A is unit triangular.
• N — INTEGER — the order of the matrix A. N >= 0.
• AP — REAL array, dimension (N*(N+1)/2) — the upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows:
  • if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
  • if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
  • If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1.
• RCOND — REAL — the reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
• WORK — REAL array, dimension (3*N).
• IWORK — INTEGER array, dimension (N).
• INFO — INTEGER — the exit-status bestie:
  • = 0: successful exit;
  • < 0: if INFO = -i, the i-th argument had an illegal value.

✨ Author ✨

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

✨ Definition at line ✨

Definition at line 128 of file stpcon.f.

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✨ Author ✨

Generated automatically by Doxygen for LAPACK from the source code.

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