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

.in +1c
.ti -1c
.RI "subroutine \fBcptrfs\fP (uplo, n, nrhs, d, e, df, ef, b, ldb, x, ldx, ferr, berr, work, rwork, info)"
.br
.RI "\fBCPTRFS\fP "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine cptrfs (character uplo, integer n, integer nrhs, real, dimension( * ) d, complex, dimension( * ) e, real, dimension( * ) df, complex, dimension( * ) ef, complex, dimension( ldb, * ) b, integer ldb, complex, dimension( ldx, * ) x, integer ldx, real, dimension( * ) ferr, real, dimension( * ) berr, complex, dimension( * ) work, real, dimension( * ) rwork, integer info)"

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

.PP
.nf
!>
!> CPTRFS improves the computed solution to a system of linear
!> equations when the coefficient matrix is Hermitian positive definite
!> and tridiagonal, and provides error bounds and backward error
!> estimates for the solution\&.
!> 
.fi
.PP
 
.RE
.PP
\fBParameters\fP
.RS 4
\fIUPLO\fP 
.PP
.nf
!>          UPLO is CHARACTER*1
!>          Specifies whether the superdiagonal or the subdiagonal of the
!>          tridiagonal matrix A is stored and the form of the
!>          factorization:
!>          = 'U':  E is the superdiagonal of A, and A = U**H*D*U;
!>          = 'L':  E is the subdiagonal of A, and A = L*D*L**H\&.
!>          (The two forms are equivalent if A is real\&.)
!> 
.fi
.PP
.br
\fIN\fP 
.PP
.nf
!>          N is INTEGER
!>          The order of the matrix A\&.  N >= 0\&.
!> 
.fi
.PP
.br
\fINRHS\fP 
.PP
.nf
!>          NRHS is INTEGER
!>          The number of right hand sides, i\&.e\&., the number of columns
!>          of the matrix B\&.  NRHS >= 0\&.
!> 
.fi
.PP
.br
\fID\fP 
.PP
.nf
!>          D is REAL array, dimension (N)
!>          The n real diagonal elements of the tridiagonal matrix A\&.
!> 
.fi
.PP
.br
\fIE\fP 
.PP
.nf
!>          E is COMPLEX array, dimension (N-1)
!>          The (n-1) off-diagonal elements of the tridiagonal matrix A
!>          (see UPLO)\&.
!> 
.fi
.PP
.br
\fIDF\fP 
.PP
.nf
!>          DF is REAL array, dimension (N)
!>          The n diagonal elements of the diagonal matrix D from
!>          the factorization computed by CPTTRF\&.
!> 
.fi
.PP
.br
\fIEF\fP 
.PP
.nf
!>          EF is COMPLEX array, dimension (N-1)
!>          The (n-1) off-diagonal elements of the unit bidiagonal
!>          factor U or L from the factorization computed by CPTTRF
!>          (see UPLO)\&.
!> 
.fi
.PP
.br
\fIB\fP 
.PP
.nf
!>          B is COMPLEX array, dimension (LDB,NRHS)
!>          The right hand side matrix B\&.
!> 
.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 COMPLEX array, dimension (LDX,NRHS)
!>          On entry, the solution matrix X, as computed by CPTTRS\&.
!>          On exit, the improved solution 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
\fIFERR\fP 
.PP
.nf
!>          FERR is REAL array, dimension (NRHS)
!>          The forward error bound for each solution vector
!>          X(j) (the j-th column of the solution matrix X)\&.
!>          If XTRUE is the true solution corresponding to X(j), FERR(j)
!>          is an estimated upper bound for the magnitude of the largest
!>          element in (X(j) - XTRUE) divided by the magnitude of the
!>          largest element in X(j)\&.
!> 
.fi
.PP
.br
\fIBERR\fP 
.PP
.nf
!>          BERR is REAL array, dimension (NRHS)
!>          The componentwise relative backward error of each solution
!>          vector X(j) (i\&.e\&., the smallest relative change in
!>          any element of A or B that makes X(j) an exact solution)\&.
!> 
.fi
.PP
.br
\fIWORK\fP 
.PP
.nf
!>          WORK is COMPLEX array, dimension (N)
!> 
.fi
.PP
.br
\fIRWORK\fP 
.PP
.nf
!>          RWORK is REAL array, dimension (N)
!> 
.fi
.PP
.br
\fIINFO\fP 
.PP
.nf
!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!> 
.fi
.PP
 
.RE
.PP
\fBInternal Parameters:\fP
.RS 4

.PP
.nf
!>  ITMAX is the maximum number of steps of iterative refinement\&.
!> 
.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
.PP

.PP
Definition at line \fB181\fP of file \fBcptrfs\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.