LAPACK 3.11.0
LAPACK: Linear Algebra PACKage

◆ dget51()

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
[in]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 )
[in]N
          N is INTEGER
          The size of the matrix.  If it is zero, DGET51 does nothing.
          It must be at least zero.
[in]A
          A is DOUBLE PRECISION array, dimension (LDA, N)
          The original (unfactored) matrix.
[in]LDA
          LDA is INTEGER
          The leading dimension of A.  It must be at least 1
          and at least N.
[in]B
          B is DOUBLE PRECISION array, dimension (LDB, N)
          The factored matrix.
[in]LDB
          LDB is INTEGER
          The leading dimension of B.  It must be at least 1
          and at least N.
[in]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
[in]LDU
          LDU is INTEGER
          The leading dimension of U.  LDU must be at least N and
          at least 1.
[in]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
[in]LDV
          LDV is INTEGER
          The leading dimension of V.  LDV must be at least N and
          at least 1.
[out]WORK
          WORK is DOUBLE PRECISION array, dimension (2*N**2)
[out]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.