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[Lapack] DSYGV test ratio

And ?? writes:
Test ratio | A Z - B Z D | / ( |A| |Z| n ulp ) is calculated for DSYGV with
itype = 1 and uplo = 'U'.

In "dsg.out", it said that "For each pair (A,B), where A is of the
given type and B is a random well-conditioned matrix. D is diagonal,
and Z is orthogonal."

In DSYGV, the input parameters are A, B, lda, ldb, etc, but without D
and Z.  And I couldn't find out the exact definition of Matrix D and
Z. I just wonder how D and Z are calculated. Can anyone give me an
explanation?

D is the diagonal matrix of generalized eigenvalues, and Z is the
orthogonal set of generalized eigenvectors.  The eigenvalues are
returned in W, and the eigenvectors are returned in A if requested by
JOBZ.  Note that both input matrices A and B are overwritten by working
data regardless of JOBZ.

Jason

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