(j3.2006) IEEE and the GPU world

[Dan Nagle]

Hello,

Has anyone examined 754 (2008) enough to know
what changes are necessary or desirable w.r.t. the definitions
of the IEEE modules supporting 754 (1985) ?

On Jun 23, 2010, at 11:27 AM, Bill Long wrote:

> 
> The IEEE feature in F03 is becoming the topic of discussion with the advent of the Chinese GPU system hitting #2 on the Top 500 list, and also users getting access to the GPU's in their laptops via schemes like OpenCL.
> 
> While GPU's support the hardware bit patterns for IEEE floating point format (more or less a requirement for them to be useful at all for floating point in a shared data environment),  they do not support things like exception flags or interrupts (halting), mainly for performance reasons.
> 
> The question is what values should users expect from routines like IEEE_SUPPORT_HALTING and IEEE_SUPPORT_FLAG?    The standard is worded as if there is a single "processor".  But the common configuration will be, at least at the beginning, of a combination of a "normal" processor (x86_64, for example) for which these inquiry functions would return true, and a GPU for which false is the right answer.   Does the presence of the GPU code pollute the entire program (functions return false no matter where called in the program), or do they return true if called in part of the code that is compiled into instructions for the normal processor, and false if called from  the parts of the code compiled for the GPU?   Note that the programmer would not necessarily know which parts of the program end up executing on which hardware type.  Insights from the designers of this feature would be particularly interesting.
> 
> Cheers,
> Bill
> 
> -- 
> Bill Long                                           longb at cray.com
> Fortran Technical Support    &                 voice: 651-605-9024
> Bioinformatics Software Development            fax:   651-605-9142
> Cray Inc./Cray Plaza, Suite 210/380 Jackson St./St. Paul, MN 55101
> 
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-- 
Cheers!

Dan Nagle