Diff: main.cpp

Revision:

0:6d89d8c13042

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Dec 06 22:37:52 2010 +0000
@@ -0,0 +1,62 @@
+#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);
+}