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//=================================================================

//

//        clock.c

//

//        Testcase for C library clock()

//

//=================================================================

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//=================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):     ctarpy, jlarmour

// Contributors:  

// Date:          1999-03-05

// Description:   Contains testcode for C library clock() function

//

//

//####DESCRIPTIONEND####

// CONFIGURATION

#include <pkgconf/libc_time.h>   // Configuration header

#include <pkgconf/system.h>

#include <pkgconf/isoinfra.h>

#include <pkgconf/infra.h>

#include <cyg/infra/testcase.h>

// This test is bound to fail often on the synthetic target -- we

// don't have exclusive access to the CPU.

#if defined(CYGPKG_HAL_SYNTH)

# define NA_MSG "Timing accuracy not guaranteed on synthetic target"

#elif !defined(CYGINT_ISO_MAIN_STARTUP)

# define NA_MSG "Requires main() startup"

#elif defined(CYGDBG_USE_TRACING)

# define NA_MSG "Cannot give an accurate test when tracing is enabled"

#endif

#ifdef NA_MSG

void

cyg_start(void)

{

    CYG_TEST_INIT();

    CYG_TEST_NA( NA_MSG );

}

#else

// INCLUDES

#include <time.h>

#include <cyg/infra/diag.h>

#include <cyg/hal/hal_cache.h>

#include <cyg/hal/hal_intr.h>

// CONSTANTS

// This defines how many loops before we decide that

// the clock doesnt work

#define MAX_TIMEOUT 100000

// Percentage error before we declare fail: range 0 - 100

#define TOLERANCE 40

// Permissible absolute deviation from mean value to take care of incorrect

// failure conclusions in case of small mean values (if absolute values of

// clock() are small, percentage variation can be large)

#define FUDGE_FACTOR 6

// Number of samples to take

#define SAMPLES 30

// We ignore ctrs[0] because it's always 0

// We ignore ctrs[1] because it will always be odd since it was

// the first measurement taken at the start of the looping, and

// the initial clock measurement (in clocks[0]) was not treated as

// part of the loop and therefore can't be considered to take the same

// time.

// We ignore ctrs[2] because it always seems to be substantially faster

// that the other samples. Probably due to cache/timing effect after the

// previous loop.

// Finally, ctrs[3] is skipped because it's also very fast on ARM targets.

#define SKIPPED_SAMPLES 6

// FUNCTIONS

static int

my_abs(int i)

{

    return (i < 0) ? -i : i;

} // my_abs()

// Clock measurement is done in a separate function so that alignment

// constraints are deterministic - some processors may perform better

// in loops that are better aligned, so by making it always the same

// function, this is prevented.

// FIXME: how do we guarantee the compiler won't inline this on -O3?

static unsigned long

clock_loop( const int timeout, clock_t prevclock, clock_t *newclock )

{

    clock_t c=0;

    long i;

    for (i=0; i<timeout; i++) {

        c = clock();

        if ( c != prevclock )

            break; // Hit the next clock pulse

    }

    if (i==timeout)

        CYG_TEST_FAIL_FINISH("No change in clock state!");

    // it should not overflow in the lifetime of this test

    if (c < prevclock)

        CYG_TEST_FAIL_FINISH("Clock decremented!");

    *newclock = c;

    return i;

} // clock_loop()

// both of these get zeroed out

static unsigned long ctrs[SAMPLES];

static clock_t clocks[SAMPLES];

int

main(int argc, char *argv[])

{

    unsigned long mean=0, sum=0, maxerr=0;

    int i;

    unsigned int absdev;

    CYG_TEST_INIT();

    CYG_TEST_INFO("Starting tests from testcase " __FILE__ " for C library "

                  "clock() function");

    // First disable the caches - they may affect the timing loops

    // below - causing the elapsed time during the clock() call to vary.

    {

        register CYG_INTERRUPT_STATE oldints;

        HAL_DISABLE_INTERRUPTS(oldints);

        HAL_DCACHE_SYNC();

        HAL_ICACHE_DISABLE();

        HAL_DCACHE_DISABLE();

        HAL_DCACHE_SYNC();

        HAL_ICACHE_INVALIDATE_ALL();

        HAL_DCACHE_INVALIDATE_ALL();

        HAL_RESTORE_INTERRUPTS(oldints);

    }

    // This waits for a clock tick, to ensure that we are at the

    // start of a clock period. Then sit in a tight loop to get

    // the clock period. Repeat this, and make sure that it the

    // two timed periods are acceptably close.

    clocks[0] = clock();

    if (clocks[0] == (clock_t)-1)  // unimplemented is potentially valid.

    {

#ifdef CYGSEM_LIBC_TIME_CLOCK_WORKING

        CYG_TEST_FAIL_FINISH( "clock() returns -1, meaning unimplemented");

#else

        CYG_TEST_PASS_FINISH( "clock() returns -1, meaning unimplemented");

#endif

    } // if

    // record clocks in a tight consistent loop to avoid random variations

    for (i=1; i<SAMPLES; i++) {

        ctrs[i] = clock_loop( MAX_TIMEOUT, clocks[i-1], &clocks[i] );

    }

    for (i=0;i<SAMPLES;i++) {

        // output what we got - useful for diagnostics of occasional

        // test failures

        diag_printf("clocks[%d] = %d, ctrs[%d] = %d\n", i, clocks[i],

                    i, ctrs[i]);

        // Now we work out the error etc.

        if (i>=SKIPPED_SAMPLES) {

            sum += ctrs[i];

        }

    }

    // deduce out the average

    mean = sum / (SAMPLES-SKIPPED_SAMPLES);

    // now go through valid results and compare against average

    for (i=SKIPPED_SAMPLES;i<SAMPLES;i++) {

        unsigned long err;

        absdev = my_abs(ctrs[i]-mean);

        // use mean+1 as divisor to avoid div-by-zero

        err = (100 * absdev) / (mean+1);

        if (err > TOLERANCE && absdev > FUDGE_FACTOR) {

            diag_printf("mean=%d, ctrs[%d]=%d, err=%d\n", mean, i, ctrs[i],

                        err);

            CYG_TEST_FAIL_FINISH("clock() within tolerance");

        }

        if (err > maxerr)

            maxerr=err;

    }

    diag_printf("mean=%d, maxerr=%d\n", mean, maxerr);

    CYG_TEST_PASS_FINISH("clock() stable");

} // main()

#endif // ifndef NA_MSG

// EOF clock.c