SRC/dpocon.f(3)

💖 SRC/dpocon.f(3) 💖

okay bestie, welcome to the Library Functions Manual side of town — this page is literally all about SRC/dpocon.f(3), and we're gonna get you fully caught up. no cap, it's giving numerical linear algebra main character energy. ✨

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🌸 NAME 🌸

SRC/dpocon.f

that's the whole name, bestie. short, sweet, iconic. 💅

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🦋 SYNOPSIS 🦋

🧩 Functions/Subroutines

       subroutine dpocon (uplo, n, a, lda, anorm, rcond, work, iwork, info)
           DPOCON

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📚 Function/Subroutine Documentation 📚

   subroutine dpocon (character uplo, integer n, double precision, dimension(
       lda, * ) a, integer lda, double precision anorm, double precision rcond,
       double precision, dimension( * ) work, integer, dimension( * ) iwork,
       integer info)
       DPOCON

🎯 Purpose

okay so DPOCON estimates the reciprocal of the condition number — specifically in the 1-norm — of a real symmetric positive definite matrix. it does this using the Cholesky factorization A = U**T*U or A = L*L**T computed by DPOTRF. 🫶

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

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

that's the vibe. mathematical, precise, slaying. 🔥

🧾 Parameters

• UPLO — UPLO is CHARACTER*1
  • = 'U': Upper triangle of A is stored;
  • = 'L': Lower triangle of A is stored.
• N — N is INTEGER. the order of the matrix A. N >= 0.
• A — A is DOUBLE PRECISION array, dimension (LDA,N). it holds the triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, as computed by DPOTRF.
• LDA — LDA is INTEGER. the leading dimension of the array A. LDA >= max(1,N).
• ANORM — ANORM is DOUBLE PRECISION. the 1-norm (or infinity-norm) of the symmetric matrix A.
• RCOND — RCOND is DOUBLE PRECISION. the reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-norm of inv(A) computed in this routine.
• WORK — WORK is DOUBLE PRECISION 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

👑 Author

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

Definition at line 119 of file dpocon.f.

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👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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