SRC/stbcon.f(3)

🎀 NAME 🎀

SRC/stbcon.f

Okay so welcome to the SRC/stbcon.f(3) page from the Library Functions Manual, bestie — it's all about STBCON, and we're gonna get into every single deet. 💖

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🌈 SYNOPSIS 🌈

✨ Functions/Subroutines ✨

Here's the icon lineup, no cap:

       subroutine stbcon (norm, uplo, diag, n, kd, ab, ldab, rcond, work,
           iwork, info)
           STBCON

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🦋 Function/Subroutine Documentation 🦋

The full signature, slayed exactly:

   subroutine stbcon (character norm, character uplo, character diag, integer
       n, integer kd, real, dimension( ldab, * ) ab, integer ldab, real rcond,
       real, dimension( * ) work, integer, dimension( * ) iwork, integer info)
       STBCON

💜 Purpose 💜

Okay so the vibe: STBCON estimates the reciprocal of the condition number of a triangular band matrix A, in either the 1-norm or the infinity-norm.

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

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

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🌸 Parameters 🌸

Every parameter, in order, with all the deets:

• NORM — NORM is CHARACTER*1. Specifies whether the 1-norm condition number or the infinity-norm condition number is required:
  • = '1' or 'O': 1-norm;
  • = 'I': Infinity-norm.
• UPLO — UPLO is CHARACTER*1
  • = 'U': A is upper triangular;
  • = 'L': A is lower triangular.
• DIAG — DIAG is CHARACTER*1
  • = 'N': A is non-unit triangular;
  • = 'U': A is unit triangular.
• N — N is INTEGER. The order of the matrix A. N >= 0.
• KD — KD is INTEGER. The number of superdiagonals or subdiagonals of the triangular band matrix A. KD >= 0.
• AB — AB is REAL array, dimension (LDAB,N). The upper or lower triangular band matrix A, stored in the first kd+1 rows of the array. The j-th column of A is stored in the j-th column of the array AB as follows:

if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).

If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1.

• LDAB — LDAB is INTEGER. The leading dimension of the array AB. LDAB >= KD+1.
• RCOND — RCOND is REAL. The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
• WORK — WORK is REAL array, dimension (3*N)
• IWORK — IWORK is INTEGER array, dimension (N)
• INFO — INFO is INTEGER

= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value

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👑 Author 👑

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

Definition at line 141 of file stbcon.f.

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🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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And that's the whole page, bestie! Cute sign-off: LAPACK Version 3.12.0 from SRC/stbcon.f(3) — that's the source/version footer energy, and we are so done. 💋✨