[CSC 435] Some hints on getting started...

[Andrew J. Pounds]

Now that some of you are finishing up the "initial profiling" assignment 
(due Wednesday night) you can start working on the re-write of dusty.

Remember -- you are rewriting in modern fortran (at least .f95 or newer 
with free-form formatted source lines) and C/C++.

One of the hard parts of this project is getting identical results 
between the old code and your new code.  If you look at the old dusty 
code it is broken up into loop sections.  I recommend working through 
each one of these individually.  In other words complete the rewrite of 
loop 10 and then compare the results of the dusty.f AV array with your 
array.  Work through each loop in this manner.

Once you hit loop 12 you will have to implement a new version of 
idcheck.  That is where things get particularly nasty and you hit some 
OLD fortran constructs that are extremely frowned upon these days.  For 
example...

  goto ( 200, 300, 400, 500 ) int(mod(i+j+k,4)+1)

is particularly troubling.  You may have to look this one up! It's 
called a computed goto statement.  You will definitely have to rewrite 
this in your new fortran.

Anyway, as you work through the code stop and verify results after each 
"loop section".   Using that strategy I was able to get everything 
rewritten and give the same results.  Once we have the codes rewritten 
in modern forms and giving the same results, we can start working on 
optimizing them.

Remember -- correct results first -- then optimization.  If you optimize 
first bad things will happen and you will most likely have to start over 
(seen it at least a dozen times in this class with this piece of code).  
At this point, just focus on the re-write and getting correct results.

-- 
*/Andrew J. Pounds, Ph.D. /* (pounds_aj at mercer.edu)
/Professor of Chemistry and Computer Science/
/Director of the Computational Science Program/
/Mercer University, Macon, GA 31207 (478) 301-5627/
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