Date: Wed, 5 Aug 2009 03:15:56 -0600 From: Sven Hammarling To: Pat Quillen Cc: Penny Anderson, Duncan Po, Cleve Moler, Bobby Cheng, lapack Subject: Re: [Lapack] xLARFP and scaling. Dear Pat, Thank you for pointing out this behaviour. Although I was not involved in writing this routine, I don't imagine that this behaviour was intended. I shall try to take a look at xLARFP in the next few days and see if I can suggest anything to improve this. As I am sure that you realise, xLARFP was written to produce a non-negative BETA, so that in a factorization such as the QR, R would have non-negative diagonals. (Although I notice that the comments in xGEQRF and xGEQR2 do not actually say that the diagonals are real and non-negative.) Best wishes, Sven.