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
- Committer:
- igor_m
- Date:
- 2010-12-06
- Revision:
- 0:6d89d8c13042
File content as of revision 0:6d89d8c13042:
#include "mbed.h" /* This program determines the time it takes to perform floating point and integer operations. To determine the time it takes, a Timer is used to measure the time it takes to complete a large amount of iterations. The time for a single operation can then be determined. To increase accuracy of the results, an empty for loop is timed to determine the loop overhead and the overhead is subtracted from the time it takes to complete the operation loop. */ #define ITERATIONS 1000000 // Number of calculations. #define CLOCK 96 // Clock freqency in MHz Timer timer; // Timer.. Serial pc(USBTX, USBRX); float number_of_cycles, single_operation_time; volatile float a, b,c; // Float operands and result. Must be volatile! //volatile int a, b,c; // Int operands and result. Must be volatile! int main() { unsigned int i, for_time, total_time, operation_time; a=2.3; b=5.33; timer.reset(); // Reset timer timer.start(); // Start timer pc.printf("Operations in progress.. May take some time.\n\n"); /* Determine loop overhead */ for (i=0; i<ITERATIONS; i++); for_time=timer.read_us(); timer.stop(); /* Determine the total loop time */ timer.reset(); timer.start(); /* The operation takes place in the body of this for loop. */ for (i=0; i<ITERATIONS; i++) { c=a+b; //c=sin(a); //c=sqrt(a); } total_time=timer.read_us(); operation_time = total_time-for_time; // Calculate the time it took for the number of operations single_operation_time=float(operation_time)/float(ITERATIONS); number_of_cycles = single_operation_time*CLOCK; pc.printf("for overhead: \t\t%dus \n", for_time); pc.printf("total time: \t\t%dus \n\n", total_time); pc.printf("%d calculations took:\t%dus \n", ITERATIONS, operation_time); pc.printf("single operation took: \t\t%fus\n", single_operation_time); pc.printf("single operation took: \t\t%.3f cycles\n", number_of_cycles); }