38 lines
804 B
C
38 lines
804 B
C
#include <sys/time.h>
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#include <stdio.h>
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// count to a billion. Time it. If it's < 1 sec, count to 10B, etc.
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unsigned long micro = 1;
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void myusec_delay(int time)
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{
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volatile unsigned long i;
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for (i = 0; i < time * micro; i++);
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}
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void myusec_calibrate_delay()
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{
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int count = 1000;
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unsigned long timeusec;
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struct timeval start, end;
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int ok = 0;
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printf("Setting up microsecond timing loop\n");
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while (!ok) {
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gettimeofday(&start, 0);
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myusec_delay(count);
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gettimeofday(&end, 0);
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timeusec = 1000000 * (end.tv_sec - start.tv_sec) +
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(end.tv_usec - start.tv_usec);
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count *= 2;
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if (timeusec < 1000000 / 4)
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continue;
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ok = 1;
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}
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// compute one microsecond. That will be count / time
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micro = count / timeusec;
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fprintf(stderr, "%ldM loops per second\n", (unsigned long) micro);
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}
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