.TH "SRC/dptcon.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*-
.ad l
.nh
.SH NAME
SRC/dptcon.f
.SH SYNOPSIS
.br
.PP
.SS "Functions/Subroutines"

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.ti -1c
.RI "subroutine \fBdptcon\fP (n, d, e, anorm, rcond, work, info)"
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.RI "\fBDPTCON\fP "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine dptcon (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision anorm, double precision rcond, double precision, dimension( * ) work, integer info)"

.PP
\fBDPTCON\fP  
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\fBPurpose:\fP
.RS 4

.PP
.nf
 DPTCON computes the reciprocal of the condition number (in the
 1-norm) of a real symmetric positive definite tridiagonal matrix
 using the factorization A = L*D*L**T or A = U**T*D*U computed by
 DPTTRF\&.

 Norm(inv(A)) is computed by a direct method, and the reciprocal of
 the condition number is computed as
              RCOND = 1 / (ANORM * norm(inv(A)))\&.
.fi
.PP
 
.RE
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\fBParameters\fP
.RS 4
\fIN\fP 
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          N is INTEGER
          The order of the matrix A\&.  N >= 0\&.
.fi
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\fID\fP 
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          D is DOUBLE PRECISION array, dimension (N)
          The n diagonal elements of the diagonal matrix D from the
          factorization of A, as computed by DPTTRF\&.
.fi
.PP
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\fIE\fP 
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.nf
          E is DOUBLE PRECISION array, dimension (N-1)
          The (n-1) off-diagonal elements of the unit bidiagonal factor
          U or L from the factorization of A,  as computed by DPTTRF\&.
.fi
.PP
.br
\fIANORM\fP 
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          ANORM is DOUBLE PRECISION
          The 1-norm of the original matrix A\&.
.fi
.PP
.br
\fIRCOND\fP 
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          RCOND is DOUBLE PRECISION
          The reciprocal of the condition number of the matrix A,
          computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is the
          1-norm of inv(A) computed in this routine\&.
.fi
.PP
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\fIWORK\fP 
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          WORK is DOUBLE PRECISION array, dimension (N)
.fi
.PP
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\fIINFO\fP 
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          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
.fi
.PP
 
.RE
.PP
\fBAuthor\fP
.RS 4
Univ\&. of Tennessee 
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Univ\&. of California Berkeley 
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Univ\&. of Colorado Denver 
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NAG Ltd\&. 
.RE
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\fBFurther Details:\fP
.RS 4

.PP
.nf
  The method used is described in Nicholas J\&. Higham, 'Efficient
  Algorithms for Computing the Condition Number of a Tridiagonal
  Matrix', SIAM J\&. Sci\&. Stat\&. Comput\&., Vol\&. 7, No\&. 1, January 1986\&.
.fi
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.RE
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.PP
Definition at line \fB117\fP of file \fBdptcon\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.