LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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◆ sget51()

subroutine sget51 ( integer  itype,
integer  n,
real, dimension( lda, * )  a,
integer  lda,
real, dimension( ldb, * )  b,
integer  ldb,
real, dimension( ldu, * )  u,
integer  ldu,
real, dimension( ldv, * )  v,
integer  ldv,
real, dimension( * )  work,
real  result 
)

SGET51

Purpose:
      SGET51  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, SGET51 does nothing.
          It must be at least zero.
[in]A
          A is REAL 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 REAL 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 REAL 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 REAL 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 REAL array, dimension (2*N**2)
[out]RESULT
          RESULT is REAL
          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.