dget51.f - Man Page

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

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.