# cptt02.f - Man Page

TESTING/LIN/cptt02.f

## Synopsis

### Functions/Subroutines

subroutine **cptt02** (uplo, n, nrhs, d, e, x, ldx, b, ldb, resid)**CPTT02**

## Function/Subroutine Documentation

### subroutine cptt02 (character uplo, integer n, integer nrhs, real, dimension( * ) d, complex, dimension( * ) e, complex, dimension( ldx, * ) x, integer ldx, complex, dimension( ldb, * ) b, integer ldb, real resid)

**CPTT02**

**Purpose:**

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.

**Parameters***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)

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **114** of file **cptt02.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page cptt02(3) is an alias of cptt02.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK