# sgtt01.f - Man Page

TESTING/LIN/sgtt01.f

## Synopsis

### Functions/Subroutines

subroutine **sgtt01** (n, dl, d, du, dlf, df, duf, du2, ipiv, work, ldwork, rwork, resid)**SGTT01**

## Function/Subroutine Documentation

### subroutine sgtt01 (integer n, real, dimension( * ) dl, real, dimension( * ) d, real, dimension( * ) du, real, dimension( * ) dlf, real, dimension( * ) df, real, dimension( * ) duf, real, dimension( * ) du2, integer, dimension( * ) ipiv, real, dimension( ldwork, * ) work, integer ldwork, real, dimension( * ) rwork, real resid)

**SGTT01**

**Purpose:**

SGTT01 reconstructs a tridiagonal matrix A from its LU factorization and computes the residual norm(L*U - A) / ( norm(A) * EPS ), where EPS is the machine epsilon.

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

*DL*DL is REAL array, dimension (N-1) The (n-1) sub-diagonal elements of A.

*D*D is REAL array, dimension (N) The diagonal elements of A.

*DU*DU is REAL array, dimension (N-1) The (n-1) super-diagonal elements of A.

*DLF*DLF is REAL array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A.

*DF*DF is REAL array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A.

*DUF*DUF is REAL array, dimension (N-1) The (n-1) elements of the first super-diagonal of U.

*DU2*DU2 is REAL array, dimension (N-2) The (n-2) elements of the second super-diagonal of U.

*IPIV*IPIV is INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.

*WORK*WORK is REAL array, dimension (LDWORK,N)

*LDWORK*LDWORK is INTEGER The leading dimension of the array WORK. LDWORK >= max(1,N).

*RWORK*RWORK is REAL array, dimension (N)

*RESID*RESID is REAL The scaled residual: norm(L*U - A) / (norm(A) * EPS)

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **132** of file **sgtt01.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page sgtt01(3) is an alias of sgtt01.f(3).

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK