# dget51.f - Man Page

TESTING/EIG/dget51.f

## Synopsis

### Functions/Subroutines

subroutine **dget51** (itype, n, a, lda, b, ldb, u, ldu, v, ldv, work, result)**DGET51**

## Function/Subroutine Documentation

### subroutine dget51 (integer itype, integer n, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldb, * ) b, integer ldb, double precision, dimension( ldu, * ) u, integer ldu, double precision, dimension( ldv, * ) v, integer ldv, double precision, dimension( * ) work, double precision result)

**DGET51**

**Purpose:**

DGET51 generally checks a decomposition of the form A = U B V' where ' means transpose and U and V are orthogonal. Specifically, if ITYPE=1 RESULT = | A - U B V' | / ( |A| n ulp ) If ITYPE=2, then: RESULT = | A - B | / ( |A| n ulp ) If ITYPE=3, then: RESULT = | I - UU' | / ( n ulp )

**Parameters***ITYPE*ITYPE is INTEGER Specifies the type of tests to be performed. =1: RESULT = | A - U B V' | / ( |A| n ulp ) =2: RESULT = | A - B | / ( |A| n ulp ) =3: RESULT = | I - UU' | / ( n ulp )

*N*N is INTEGER The size of the matrix. If it is zero, DGET51 does nothing. It must be at least zero.

*A*A is DOUBLE PRECISION array, dimension (LDA, N) The original (unfactored) matrix.

*LDA*LDA is INTEGER The leading dimension of A. It must be at least 1 and at least N.

*B*B is DOUBLE PRECISION array, dimension (LDB, N) The factored matrix.

*LDB*LDB is INTEGER The leading dimension of B. It must be at least 1 and at least N.

*U*U is DOUBLE PRECISION array, dimension (LDU, N) The orthogonal matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2

*LDU*LDU is INTEGER The leading dimension of U. LDU must be at least N and at least 1.

*V*V is DOUBLE PRECISION array, dimension (LDV, N) The orthogonal matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2

*LDV*LDV is INTEGER The leading dimension of V. LDV must be at least N and at least 1.

*WORK*WORK is DOUBLE PRECISION array, dimension (2*N**2)

*RESULT*RESULT is DOUBLE PRECISION The values computed by the test specified by ITYPE. The value is currently limited to 1/ulp, to avoid overflow. Errors are flagged by RESULT=10/ulp.

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **147** of file **dget51.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dget51(3) is an alias of dget51.f(3).

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