cptrfs.f3

!>
!> 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.
!> 

UPLO

!>          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.)
!> 

N

!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!> 

NRHS

!>          NRHS is INTEGER
!>          The number of right hand sides, i.e., the number of columns
!>          of the matrix B.  NRHS >= 0.
!> 

D

!>          D is REAL array, dimension (N)
!>          The n real diagonal elements of the tridiagonal matrix A.
!> 

E

!>          E is COMPLEX array, dimension (N-1)
!>          The (n-1) off-diagonal elements of the tridiagonal matrix A
!>          (see UPLO).
!> 

DF

!>          DF is REAL array, dimension (N)
!>          The n diagonal elements of the diagonal matrix D from
!>          the factorization computed by CPTTRF.
!> 

EF

!>          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).
!> 

B

!>          B is COMPLEX array, dimension (LDB,NRHS)
!>          The right hand side matrix B.
!> 

LDB

!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= max(1,N).
!> 

X

!>          X is COMPLEX array, dimension (LDX,NRHS)
!>          On entry, the solution matrix X, as computed by CPTTRS.
!>          On exit, the improved solution matrix X.
!> 

LDX

!>          LDX is INTEGER
!>          The leading dimension of the array X.  LDX >= max(1,N).
!> 

FERR

!>          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).
!> 

BERR

!>          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).
!> 

WORK

!>          WORK is COMPLEX array, dimension (N)
!> 

RWORK

!>          RWORK is REAL array, dimension (N)
!> 

INFO

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!> 

!>  ITMAX is the maximum number of steps of iterative refinement.
!> 

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