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### [Scalapack] complex pivoted qr factorisation

 ```Yes, that is the order I find, which I have tested on two machines. I forgot to mention that when the numbers are exactly 0.5 and 0.0, the order comes out correctly. Also, the output matrices still multiply to give the original matrix. Only the pivoting appears to be wrong. David On 20 October 2011 04:28, James Demmel wrote: ``````There was a relatively recently repaired bug of this kind in the LAPACK code; the problem was that when some R(i,i) is very tiny (as in the examples below), cancellation from updating the column norms can cause them to be inaccurate and not reflect the true R(i,i) values, which then do not appear in sorted order. But that should not cause R(2,2) and R(3,3) in the first example below to come out in the wrong order, since they are of vastly different magnitudes. Is this really the wrong order that appeared? Jim On 10/19/11 10:07 AM, James, Rodney wrote: `````` Hello David, Thank you for the report. ?It looks like this is probably a bug -- we will take a look at this and hopefully get a fix in place sometime in the near future. --Rodney On Oct 18, 2011, at 9:32 PM, David Wang wrote: ``````Hello Scalapack, I have been using the pivoted QR factorisation routine (pzgeqpf) from scalapack-1.8.0. ?I have found that, in some cases, the diagonal elements of the R matrix are not arranged in order of descending magnitude as described in the user's guide. ?I have attached a test case for you to verify. ?e.g. I get something like: R(0,0) -0.707107 + 0i R(1,1) -0.707107 + 0i R(2,2) 8.16273e-17 + 0i R(3,3) -0.243173 + 0i R(4,4) 4.82605e-17 + 0i This behaviour can be reproduced for the single precision complex case (although not with the supplied test matrix). ?The same test case works for the real case (pdgeqpf). ?e.g. R(0,0) -0.707107 R(1,1) -0.707107 R(2,2) 0.5 R(3,3) 3.96991e-17 R(4,4) 2.2336e-17 I have not had any problems with the equivalent lapack routines (zgeqp3), and have not see any mention of this in the errata. David _______________________________________________ Scalapack mailing list Scalapack@Domain.Removed http://lists.eecs.utk.edu/mailman/listinfo/scalapack `````` _______________________________________________ Scalapack mailing list Scalapack@Domain.Removed http://lists.eecs.utk.edu/mailman/listinfo/scalapack `````` `````` ```
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