topic Re: IML proc results and sas version in SAS/IML Software and Matrix Computations

IML proc results and sas version

LineMoon — Tue, 07 Feb 2017 22:38:17 GMT

Hello experts,

We can observe that for the same treatement, there is a differente between the results given by IML SAS 9.2 proc and SAS 9.4.

Please, why ?

Re: IML proc results and sas version

Reeza — Tue, 07 Feb 2017 23:10:35 GMT

Can you post an example so we can replicate your issue?

Re: IML proc results and sas version

ballardw — Tue, 07 Feb 2017 23:43:00 GMT

Is the SAS 9.2 a 32 bit or 64 bit machine? The more bits involved in the processor the more likelihood for different rounding of values from internal data storage.

Also the algorithms in the SAS code have likely been changed somewhat for any number of reasons.

How great are the differences you are seeing?

Re: IML proc results and sas version

LineMoon — Wed, 08 Feb 2017 00:00:45 GMT

sas 9.2 is under unix.

Small difference is less than 10^(-16)

Re: IML proc results and sas version

ballardw — Wed, 08 Feb 2017 00:40:17 GMT

@LineMoon wrote:

sas 9.2 is under unix.

Small difference is less than 10^(-16)

IIRC Unix SAS carries two more digits of precision than windows. And that difference is almost certainly precison of storage between the two systems. If the difference showed up in the 10^(-6) range I would contact SAS Tech support to see what may be going on.

Re: IML proc results and sas version

Rick_SAS — Wed, 08 Feb 2017 13:29:24 GMT

If you search "differences sas 9.2" on the Support Communities, you will see many questions of this type. To copy/paste from one of my previous answers:

"Major releases (like from 9.2 to 9.3) are when SAS updates compilers and other software development tools. Because optimizing compilers change the instruction set for optimized assembly, and because optimization is inherently a nonlinear dynamical system small changes in the way that the compilers optimize code can result in different results from MLE methods. "

Other differences result from changes in SAS code, including fixing bugs, changing to better algorithms, multithreading, and so forth. Changes on the order of machine precision (1E-16) are not numerically significant.

Re: IML proc results and sas version

LineMoon — Wed, 08 Feb 2017 21:15:24 GMT

Thank you very much