.TH "TESTING/LIN/dptt05.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*-
.ad l
.nh
.SH NAME
TESTING/LIN/dptt05.f
.SH SYNOPSIS
.br
.PP
.SS "Functions/Subroutines"

.in +1c
.ti -1c
.RI "subroutine \fBdptt05\fP (n, nrhs, d, e, b, ldb, x, ldx, xact, ldxact, ferr, berr, reslts)"
.br
.RI "\fBDPTT05\fP "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine dptt05 (integer n, integer nrhs, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision, dimension( ldb, * ) b, integer ldb, double precision, dimension( ldx, * ) x, integer ldx, double precision, dimension( ldxact, * ) xact, integer ldxact, double precision, dimension( * ) ferr, double precision, dimension( * ) berr, double precision, dimension( * ) reslts)"

.PP
\fBDPTT05\fP 
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\fBPurpose:\fP
.RS 4

.PP
.nf
!>
!> DPTT05 tests the error bounds from iterative refinement for the
!> computed solution to a system of equations A*X = B, where A is a
!> symmetric tridiagonal matrix of order n\&.
!>
!> RESLTS(1) = test of the error bound
!>           = norm(X - XACT) / ( norm(X) * FERR )
!>
!> A large value is returned if this ratio is not less than one\&.
!>
!> RESLTS(2) = residual from the iterative refinement routine
!>           = the maximum of BERR / ( NZ*EPS + (*) ), where
!>             (*) = NZ*UNFL / (min_i (abs(A)*abs(X) +abs(b))_i )
!>             and NZ = max\&. number of nonzeros in any row of A, plus 1
!> 
.fi
.PP
 
.RE
.PP
\fBParameters\fP
.RS 4
\fIN\fP 
.PP
.nf
!>          N is INTEGER
!>          The number of rows of the matrices X, B, and XACT, and the
!>          order of the matrix A\&.  N >= 0\&.
!> 
.fi
.PP
.br
\fINRHS\fP 
.PP
.nf
!>          NRHS is INTEGER
!>          The number of columns of the matrices X, B, and XACT\&.
!>          NRHS >= 0\&.
!> 
.fi
.PP
.br
\fID\fP 
.PP
.nf
!>          D is DOUBLE PRECISION array, dimension (N)
!>          The n diagonal elements of the tridiagonal matrix A\&.
!> 
.fi
.PP
.br
\fIE\fP 
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.nf
!>          E is DOUBLE PRECISION array, dimension (N-1)
!>          The (n-1) subdiagonal elements of the tridiagonal matrix A\&.
!> 
.fi
.PP
.br
\fIB\fP 
.PP
.nf
!>          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
!>          The right hand side vectors for the system of linear
!>          equations\&.
!> 
.fi
.PP
.br
\fILDB\fP 
.PP
.nf
!>          LDB is INTEGER
!>          The leading dimension of the array B\&.  LDB >= max(1,N)\&.
!> 
.fi
.PP
.br
\fIX\fP 
.PP
.nf
!>          X is DOUBLE PRECISION array, dimension (LDX,NRHS)
!>          The computed solution vectors\&.  Each vector is stored as a
!>          column of the matrix X\&.
!> 
.fi
.PP
.br
\fILDX\fP 
.PP
.nf
!>          LDX is INTEGER
!>          The leading dimension of the array X\&.  LDX >= max(1,N)\&.
!> 
.fi
.PP
.br
\fIXACT\fP 
.PP
.nf
!>          XACT is DOUBLE PRECISION array, dimension (LDX,NRHS)
!>          The exact solution vectors\&.  Each vector is stored as a
!>          column of the matrix XACT\&.
!> 
.fi
.PP
.br
\fILDXACT\fP 
.PP
.nf
!>          LDXACT is INTEGER
!>          The leading dimension of the array XACT\&.  LDXACT >= max(1,N)\&.
!> 
.fi
.PP
.br
\fIFERR\fP 
.PP
.nf
!>          FERR is DOUBLE PRECISION array, dimension (NRHS)
!>          The estimated forward error bounds for each solution vector
!>          X\&.  If XTRUE is the true solution, FERR bounds the magnitude
!>          of the largest entry in (X - XTRUE) divided by the magnitude
!>          of the largest entry in X\&.
!> 
.fi
.PP
.br
\fIBERR\fP 
.PP
.nf
!>          BERR is DOUBLE PRECISION array, dimension (NRHS)
!>          The componentwise relative backward error of each solution
!>          vector (i\&.e\&., the smallest relative change in any entry of A
!>          or B that makes X an exact solution)\&.
!> 
.fi
.PP
.br
\fIRESLTS\fP 
.PP
.nf
!>          RESLTS is DOUBLE PRECISION array, dimension (2)
!>          The maximum over the NRHS solution vectors of the ratios:
!>          RESLTS(1) = norm(X - XACT) / ( norm(X) * FERR )
!>          RESLTS(2) = BERR / ( NZ*EPS + (*) )
!> 
.fi
.PP
 
.RE
.PP
\fBAuthor\fP
.RS 4
Univ\&. of Tennessee 

.PP
Univ\&. of California Berkeley 

.PP
Univ\&. of Colorado Denver 

.PP
NAG Ltd\&. 
.RE
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Definition at line \fB148\fP of file \fBdptt05\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.