Igor Martinovski
This is a simple program that can be used to determine how long a single operation takes. The program outputs the results in microseconds and number of clock cycles.
main.cpp@0:6d89d8c13042, 2010-12-06 (annotated)
- Committer:
- igor_m
- Date:
- Mon Dec 06 22:37:52 2010 +0000
- Revision:
- 0:6d89d8c13042
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| igor_m | 0:6d89d8c13042 | 1 | #include "mbed.h" |
| igor_m | 0:6d89d8c13042 | 2 | /* This program determines the time it takes to perform floating point |
| igor_m | 0:6d89d8c13042 | 3 | and integer operations. |
| igor_m | 0:6d89d8c13042 | 4 | To determine the time it takes, a Timer is used to measure the time |
| igor_m | 0:6d89d8c13042 | 5 | it takes to complete a large amount of iterations. The time for a single |
| igor_m | 0:6d89d8c13042 | 6 | operation can then be determined. |
| igor_m | 0:6d89d8c13042 | 7 | |
| igor_m | 0:6d89d8c13042 | 8 | To increase accuracy of the results, an empty for loop is timed to determine |
| igor_m | 0:6d89d8c13042 | 9 | the loop overhead and the overhead is subtracted from the time it takes to |
| igor_m | 0:6d89d8c13042 | 10 | complete the operation loop. |
| igor_m | 0:6d89d8c13042 | 11 | |
| igor_m | 0:6d89d8c13042 | 12 | */ |
| igor_m | 0:6d89d8c13042 | 13 | #define ITERATIONS 1000000 // Number of calculations. |
| igor_m | 0:6d89d8c13042 | 14 | #define CLOCK 96 // Clock freqency in MHz |
| igor_m | 0:6d89d8c13042 | 15 | Timer timer; // Timer.. |
| igor_m | 0:6d89d8c13042 | 16 | |
| igor_m | 0:6d89d8c13042 | 17 | Serial pc(USBTX, USBRX); |
| igor_m | 0:6d89d8c13042 | 18 | float number_of_cycles, single_operation_time; |
| igor_m | 0:6d89d8c13042 | 19 | volatile float a, b,c; // Float operands and result. Must be volatile! |
| igor_m | 0:6d89d8c13042 | 20 | //volatile int a, b,c; // Int operands and result. Must be volatile! |
| igor_m | 0:6d89d8c13042 | 21 | |
| igor_m | 0:6d89d8c13042 | 22 | int main() { |
| igor_m | 0:6d89d8c13042 | 23 | |
| igor_m | 0:6d89d8c13042 | 24 | unsigned int i, for_time, total_time, operation_time; |
| igor_m | 0:6d89d8c13042 | 25 | a=2.3; |
| igor_m | 0:6d89d8c13042 | 26 | b=5.33; |
| igor_m | 0:6d89d8c13042 | 27 | |
| igor_m | 0:6d89d8c13042 | 28 | timer.reset(); // Reset timer |
| igor_m | 0:6d89d8c13042 | 29 | timer.start(); // Start timer |
| igor_m | 0:6d89d8c13042 | 30 | pc.printf("Operations in progress.. May take some time.\n\n"); |
| igor_m | 0:6d89d8c13042 | 31 | /* Determine loop overhead */ |
| igor_m | 0:6d89d8c13042 | 32 | for (i=0; i<ITERATIONS; i++); |
| igor_m | 0:6d89d8c13042 | 33 | for_time=timer.read_us(); |
| igor_m | 0:6d89d8c13042 | 34 | timer.stop(); |
| igor_m | 0:6d89d8c13042 | 35 | |
| igor_m | 0:6d89d8c13042 | 36 | /* Determine the total loop time */ |
| igor_m | 0:6d89d8c13042 | 37 | timer.reset(); |
| igor_m | 0:6d89d8c13042 | 38 | timer.start(); |
| igor_m | 0:6d89d8c13042 | 39 | |
| igor_m | 0:6d89d8c13042 | 40 | /* The operation takes place in the body of |
| igor_m | 0:6d89d8c13042 | 41 | this for loop. */ |
| igor_m | 0:6d89d8c13042 | 42 | |
| igor_m | 0:6d89d8c13042 | 43 | for (i=0; i<ITERATIONS; i++) { |
| igor_m | 0:6d89d8c13042 | 44 | |
| igor_m | 0:6d89d8c13042 | 45 | c=a+b; |
| igor_m | 0:6d89d8c13042 | 46 | //c=sin(a); |
| igor_m | 0:6d89d8c13042 | 47 | //c=sqrt(a); |
| igor_m | 0:6d89d8c13042 | 48 | |
| igor_m | 0:6d89d8c13042 | 49 | } |
| igor_m | 0:6d89d8c13042 | 50 | total_time=timer.read_us(); |
| igor_m | 0:6d89d8c13042 | 51 | |
| igor_m | 0:6d89d8c13042 | 52 | operation_time = total_time-for_time; // Calculate the time it took for the number of operations |
| igor_m | 0:6d89d8c13042 | 53 | |
| igor_m | 0:6d89d8c13042 | 54 | single_operation_time=float(operation_time)/float(ITERATIONS); |
| igor_m | 0:6d89d8c13042 | 55 | number_of_cycles = single_operation_time*CLOCK; |
| igor_m | 0:6d89d8c13042 | 56 | |
| igor_m | 0:6d89d8c13042 | 57 | pc.printf("for overhead: \t\t%dus \n", for_time); |
| igor_m | 0:6d89d8c13042 | 58 | pc.printf("total time: \t\t%dus \n\n", total_time); |
| igor_m | 0:6d89d8c13042 | 59 | pc.printf("%d calculations took:\t%dus \n", ITERATIONS, operation_time); |
| igor_m | 0:6d89d8c13042 | 60 | pc.printf("single operation took: \t\t%fus\n", single_operation_time); |
| igor_m | 0:6d89d8c13042 | 61 | pc.printf("single operation took: \t\t%.3f cycles\n", number_of_cycles); |
| igor_m | 0:6d89d8c13042 | 62 | } |