[CSC 435] Optimization Questions

[Andrew J. Pounds]

I would do a comparison of -O2 and -O3 against the baseline to 
demonstrate that they do make a difference.  Then the question is will 
all of your optimizations produce the same results at -O3 -- or do you 
have to back down to -O2.

That being said, here is what I recommend.

1. Create your baseline and then do the -O, -O2, -O3 comparison on one 
chart.

2.  Then try out the -march -mtune option to see if that helps.  Use the 
highest level of optimization from above that gives consistent results.

Once you have done these things (which we will count as two optimization 
steps) you should be ready to demonstrate how any code rewriting you do 
impacts optimization.  The problem here is that some of your code 
rewriting - coupled to the optimization flags - may impact your 
results.  For that reason you should try to pick the optimization level 
above that works consistently across all of your code rewriting 
optimizations.  Your ultimate goal is to produce faster code that gives 
identical results.  If you come up with something that dramatically 
increases the speed of the code, but slightly modifies the results, then 
count that as a good optimization but demonstrate the differences it 
produces in your paper and be able to explain why you think that is 
happening.

Does that help?



On 02/27/2016 10:23 AM, Nicholas Allan Rasmuson wrote:
>
> Dr. Pounds:
>
>     For the optimizations do you want me to count things like 
> differing compiler flags as their own optimizations and run 
> them separately? Such as testing -O2 and -O3 as well as the cpu base 
> flag as three separate optimizations and graph the effects, or lack 
> thereof, as such?
>
> Sincerely,
>
> Nicholas Rasmuson
>

-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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