LAPACK Archives

[Lapack] possible problem in pxstein (scalapack)

On Thu, 2012-02-09 at 16:24 +0100, Ake Sandgren wrote:

Not sure if this is a real problem or not...
pxstein are doing the following

ONENRM = ABS( D( B1 ) ) + ABS( E( B1 ) )
ONENRM = MAX( ONENRM, ABS( D( BN ) )+ABS( E( BN-1 ) ) )

That last E(bn-1) will sometimes ref e(0)
and the following do loop will ref e(-1) when bn=1
DO 120 J = B1 + 1, BN - 1
ONENRM = MAX( ONENRM, ABS( D( J ) )+ABS( E( J-1 ) )+ ...

was a bit tired when reading the code. the do-loop is safe as long as b1
= 1 which it should be unless there are other bugs lurking :-)

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