DSYCON(3)

💖 DSYCON(3) — Library Functions Manual 💖

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🦋 NAME 🦋

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dsycon.f

That's the file, bestie. No cap.

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✨ SYNOPSIS ✨

Functions/Subroutines

       subroutine DSYCON (uplo, n, a, lda, ipiv, anorm, rcond, work, iwork,
           info)
           DSYCON

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🫶 Function/Subroutine Documentation 🫶

The signature is literally this, exactly this, do not come for me:

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

🎀 Purpose 🎀

DSYCON estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF 💖

It gets an estimate for norm(inv(A)), and then the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))). That's the whole vibe ✨

💅 Parameters 💅

• UPLO — is CHARACTER*1; specifies whether the details of the factorization are stored as an upper or lower triangular matrix.
  • = 'U': Upper triangular, form is A = U*D*U**T;
  • = 'L': Lower triangular, form is A = L*D*L**T.
• N — is INTEGER; the order of the matrix A. N >= 0.
• A — is DOUBLE PRECISION array, dimension (LDA,N); the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by DSYTRF.
• LDA — is INTEGER; the leading dimension of the array A. LDA >= max(1,N).
• IPIV — is INTEGER array, dimension (N); details of the interchanges and the block structure of D as determined by DSYTRF.
• ANORM — is DOUBLE PRECISION; the 1-norm of the original matrix A.
• 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 — is DOUBLE PRECISION array, dimension (2*N).
• IWORK — is INTEGER array, dimension (N).
• 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 128 of file dsycon.f.

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👑 Author 👑

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