We are going to be working on a CERN project called Drive_God_Lin (more info soon...)
I decided to profile CERN project - Drive_God_Lin. After gprof the project with the test data provided I learned the following:
(summery of gprof)
Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls ms/call ms/call name 39.98 26.68 26.68 524 50.92 50.92 ordres_ 37.42 51.65 24.97 314400 0.08 0.08 zfunr_ 12.69 60.12 8.47 314400 0.03 0.03 cfft_ ...
As you can see, most the program's time is spent in the ordres() subroutine and zfunr() subroutine; both are localed in the fortran portion of the program (there is a c portion as well).
Furthermore, this program is already parallelized using OpenMP; which means it may be farther parallelized using cuda technology.
In these two subroutines (specially in orders()) there are a lot of nested loops, if statements, goto's, and even some sore of a search algorithm (in orders() only) that I'm certain it could be notably improved using cuda technology.
The project is on github here
I profiled CERN's Drive_God_Lin application.
The resulting profile is generated using gprof.
% cumulative self self total time seconds seconds calls ms/call ms/call name 49.47 10.34 10.34 314400 0.03 0.03 zfunr_ 28.76 16.35 6.01 524 11.47 11.47 ordres_ 10.81 18.61 2.26 314400 0.01 0.01 cfft_ 3.30 19.30 0.69 314400 0.00 0.04 tunelasr_ 3.06 19.94 0.64 1048 0.61 13.63 spectrum_ 1.67 20.29 0.35 314400 0.00 0.00 calcr_
All other functions took less than 1% of the application's run time,
so I am not considering them when assessing which parts of the application need to be optimized,
as the speed increase would be negligible.
In total, the application ran for 20.90 seconds using 1 core.
The specifications of the system being used to generate this profile was:
Ubuntu 12.04 LTS 32-bit Intel® Core™2 Quad CPU Q9550 @ 2.83GHz × 4 3.9 GB Memory NVIDIA GTX 480
The 3 most problematic functions are zfunr_ , ordres_ , and cfft.
1. zfunr_ takes up almost 49.5% of the application processing time, and it is also called 314,400 times. It is possible that this time can be significantly increased using a many-core GPU to run hundreds of threads simultaneously.
2. cfft_ is called just as much as the zfunr_ function, but it takes significantly less time in the application. It is likely that this function can be optimized to use the GPU, however the speed increase may be minimal compared to the zfunr_ function.
3. The ordres_ function takes 28.76% of the application time, but is only called 524 times throughout the application. This subroutine is used to order harmonics, and is incredibly long. Depending on the ordering algorithm used in this subroutine, it may be possible to optimize the serial performance of the subroutine before further optimizing it to use the GPU.
4. Many other functions are called thousands of times throughout the application. It may be possible to optimize some of these to attain a minuscule speed increase, assuming the memory read/write rate between the GPU and CPU doesn't increase run-time instead. However it is clear that these functions are not priority.
It is important to note that the application currently uses OpenMP,
so multi-core processing can be used. When set to utilize 12 threads,
the program finishes in around 5 seconds.
I have forked a copy of the code into my own GitHub repository here
For assignment one I profiled a closest pair algorithm. The source code can be found here:
I was able to run the code successfully on Matrix and I believe it is a good candidate to parallelize. The closest() function generally eats up the most time and I believe that most of its remedial processes could be done by the GPU.
A useful reference site to help explain closest pair algorithms: