This program is a simple test that permutes loops so that a function scans a three dimensional array with a stride-1 reference pattern (good locality) versus a stride-MN reference pattern (bad locality).
Just run make, it should work on most Linux systems.
./localitytest [iterations]
Where iterations is the number of times to run the loops. You can skip the argument for a default of 100 iterations.
The program will tell you
- Input
- How many iterations it will be running
- Size of test array (hardcoded at the moment)
- Output
- How long time is spent running the loops with bad locality
- How long time is spent running the loops with good locality
- The difference between the two
Here are a couple outputs when run on my machine:
$ ./localitytest 1000
Running test with 1000 iterations.
Test array is 2304000 bytes in size.
Time spent running bad locality: 2.531270113 sec.
Time spent running good locality: 1.863334975 sec.
Difference between averages: 0.667935138 sec.
$ ./localitytest 10000
Running test with 10000 iterations.
Test array is 2304000 bytes in size.
Time spent running bad locality: 25.254116078 sec.
Time spent running good locality: 18.713775802 sec.
Difference between averages: 6.540340276 sec.
Author:
Freyr Bergsteinsson freyrb12@ru.is
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
