DDISNA(3)

💅 DDISNA(3) 💅

okay so bestie, welcome to the ddisna.f(3) page from the Library Functions Manual. this is the whole lowdown on DDISNA, and yes, it’s giving linear-algebra main character energy. ✨

🌸 NAME 🌸

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

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine DDISNA (job, m, n, d, sep, info)
    DDISNA

🎀 Function/Subroutine Documentation 🎀

subroutine DDISNA (character job, integer m, integer n, double precision, dimension( * ) d, double precision, dimension( * ) sep, integer info)
    DDISNA

💖 Purpose 💖

okay so DDISNA computes the reciprocal condition numbers for the eigenvectors of a real symmetric or complex Hermitian matrix, or for the left or right singular vectors of a general m-by-n matrix. the reciprocal condition number is the 'gap' between the corresponding eigenvalue or singular value and the nearest other one. no cap. 🦋

the bound on the error, measured by angle in radians, in the I-th computed vector is given by:

DLAMCH( 'E' ) * ( ANORM / SEP( I ) )

where ANORM = 2-norm(A) = max( abs( D(j) ) ). SEP(I) is not allowed to be smaller than DLAMCH( 'E' )*ANORM in order to limit the size of the error bound. 💅

DDISNA may also be used to compute error bounds for eigenvectors of the generalized symmetric definite eigenproblem. 🌈

🦋 Parameters 🦋

🔥 JOB 🔥

JOB is CHARACTER*1. it specifies for which problem the reciprocal condition numbers should be computed:

• 'E': the eigenvectors of a symmetric/Hermitian matrix;
• 'L': the left singular vectors of a general matrix;
• 'R': the right singular vectors of a general matrix.

🍓 M 🍓

M is INTEGER. the number of rows of the matrix. M >= 0.

🌸 N 🌸

N is INTEGER. if JOB = 'L' or 'R', the number of columns of the matrix, in which case N >= 0. ignored if JOB = 'E'.

🦋 D 🦋

D is DOUBLE PRECISION array, dimension (M) if JOB = 'E', dimension (min(M,N)) if JOB = 'L' or 'R'. the eigenvalues (if JOB = 'E') or singular values (if JOB = 'L' or 'R') of the matrix, in either increasing or decreasing order. if singular values, they must be non-negative.

🎀 SEP 🎀

SEP is DOUBLE PRECISION array, dimension (M) if JOB = 'E', dimension (min(M,N)) if JOB = 'L' or 'R'. the reciprocal condition numbers of the vectors.

💀 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 116 of file ddisna.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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signed off with love by LAPACK, Version 3.12.0, from /home/abui...RC/ddisna.f(3). 💖✨