CPTT02 computes the residual for the solution to a symmetric


 tridiagonal system of equations:


    RESID = norm(B - A*X) / (norm(A) * norm(X) * EPS),


 where EPS is the machine epsilon.

UPLO

          UPLO is CHARACTER*1


          Specifies whether the superdiagonal or the subdiagonal of the


          tridiagonal matrix A is stored.


          = 'U':  E is the superdiagonal of A


          = 'L':  E is the subdiagonal of A

N

          N is INTEGER


          The order of the matrix A.

NRHS

          NRHS is INTEGER


          The number of right hand sides, i.e., the number of columns


          of the matrices B and X.  NRHS >= 0.

D

          D is REAL array, dimension (N)


          The n diagonal elements of the tridiagonal matrix A.

E

          E is COMPLEX array, dimension (N-1)


          The (n-1) subdiagonal elements of the tridiagonal matrix A.

X

          X is COMPLEX array, dimension (LDX,NRHS)


          The n by nrhs matrix of solution vectors X.

LDX

          LDX is INTEGER


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

B

          B is COMPLEX array, dimension (LDB,NRHS)


          On entry, the n by nrhs matrix of right hand side vectors B.


          On exit, B is overwritten with the difference B - A*X.

LDB

          LDB is INTEGER


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

RESID

          RESID is REAL


          norm(B - A*X) / (norm(A) * norm(X) * EPS)

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