Data Structures & Algorithms Lecture Notes

5 November 2010 • Performance Measurement in Practice (in Java)

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This C macro

#define timeit(et, stmts) \
   {struct timeb _ts; \
    register int _i; \
    (void) ftime(&_ts); \
    et = _ts.time*1000 + _ts.millitm; \
    for (_i = 0; _i < loop_maximum; _i++) { stmts ; } \
    (void) ftime(&_ts); \
    et = _ts.time*1000 + _ts.millitm - et; }1

can be used to measure the execution time of practically any C code segment. For example:

time_t s;

timeit(s,
  (void) fwrite(c, sizeof(char), write_size, f);
  (void) fflush(f));

measures the cost of writing all the way out to disk some number (given by write_size) of characters.

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