[Linux-ia64] Itanium gets supercomputing software

Richard Walsh rbw at ahpcrc.org
Tue Apr 15 11:08:20 EDT 2003


On Tue Apr 15 09:45:03 2003, Joseph Landman wrote:

>I remember the Trace Multiflow in 1991 or so, where compiling my
>molecular dynamics code took the better part of a day.  Made debugging
>interesting, as the "bug" only appeared in the optimized code.

 Don't think EPIC compile times compare to those of the MultiFlow, but
 I have no direct experience.  
 
 I do think EPIC is valuable on several scores.  First, it frees real 
 estate on the chip by reducing/eliminatin out-of-order execution hardware 
 allowing for larger caches (3 MB on chip today) and future additional 
 functional unit parallelism or additional cores on the same chip.  Second,
 it allows generated code to be tuned to the width (number of simultaneous 
 instructions alowed) of the processor. Finally, its predicate/nat analysis 
 can completely remove traditional stall points where the CPU must wait 
 for data from memory or conditions to be computed before proceeding to 
 execution.  The last advantage is a useful way of using increasingly 
 redundant core hardware to speed results through the processor.  "Micro-
 threads/paths" are simultaneously computed using hardware that for the 
 moment would be idle anyway and results that are later proven to 
 to un-needed are be discarded. 

 The benefits are hard to quantify, but I believe significant part
 of the I2's SpecFP score is EPIC derived.

 I am guessing others disagree ... ;-) ... Oui?

 rbw

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