1

edit
# Changes

→Assignment 3

'''Problem Description'''

In the second assignment our team had two options to select from. These options were either a prime number calculator or a calculator of Pi. After some discussion, we selected to work with the PI calculation problem. We took Norbert’s original CPU program and we ported it to the GPU which sped up the processing rate, resulting in a faster processing time overall. In this assignment we experimented more with our CUDA solution and utilizing two different forms of optimization, we managed to get an even faster computation speed of the overall program.

'''Optimization 1'''

One of the main problems of our previous solution was that it was taking a much longer execution time than we were expecting. During the analysis of the program, we realized that we were wasting precious computation time in generating random numbers on the host and copying them over to the device. For this reason we decided to generate the random numbers directly on the device using cuRAND. This allowed us to reduce the run time to a quarter of what it took to run before.

The following code sample demonstrates this optimization:

[[File:A3p1.PNG]]

'''Optimization 2'''

The second optimization we made was that we implemented a reduction algorithm to help with a couple of things. Firstly it lessened the amount of data being copied from the GPU from a potential 60 million integers to just 65 thousand integers which ends up being ~923 times less items to copy. Secondly and most importantly, it did most of the additions and made it much faster (less iterations) to add up the remaining partial sums. We also implemented the thread divergence method in the reduction algorithm for even better results. This method halved the time required after our initial optimization, effectively reducing the total run time by an eighth of the original time.

The following code sample demonstrate this optimization:

[[File:A3P2.PNG]]

'''Program execution '''

The following table and chart compare the original CPU runtime to the GPU runtime with the final optimized runtime.

[[File:A3P3.PNG ]]

[[File:A3P4.PNG |1100px]]

'''Conclusion'''