Re: [PATCH i-g-t v2] tests/kms_flip: Adjust tolerance when counting frames

[Gabriel Feceoru <gabriel.feceoru@intel.com>]

On 10.05.2016 18:39, Jani Nikula wrote:
> On Tue, 10 May 2016, Gabriel Feceoru <gabriel.feceoru@intel.com> wrote:
>> If count == 100 and expected == 99 this condition fails (99*101/100 = 99.99).
>>
>> (v2): Increased the tolerance range, as suggested by Jani.
>>
>> Cc: Jani Nikula <jani.nikula@intel.com>
>> Cc: Daniel Vetter <daniel.vetter@intel.com>
>> Signed-off-by: Gabriel Feceoru <gabriel.feceoru@intel.com>
>> ---
>>   tests/kms_flip.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tests/kms_flip.c b/tests/kms_flip.c
>> index eda2fcc..ceb0e0b 100644
>> --- a/tests/kms_flip.c
>> +++ b/tests/kms_flip.c
>> @@ -1187,7 +1187,7 @@ static void check_final_state(struct test_output *o, struct event_state *es,
>>
>>   		count *= o->seq_step;
>>   		expected = elapsed / frame_time(o);
>> -		igt_assert_f(count >= expected * 99/100 && count <= expected * 101/100,
>> +		igt_assert_f(count >= expected * 98/100 && count <= expected * 102/100,
>
> I was thinking of
>
> #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
>
> igt_assert_f(count >= expected * 99 / 100 &&
>               count <= DIV_ROUND_UP(expected * 101, 100));
>
> but maybe someone who knows how accurate this should really be could
> chime in.
>
> BR,
> Jani.

I've just realized that frame_time(0) is a float, so converting to int 
in that division will lose precision.

Proposing this now:

diff --git a/tests/kms_flip.c b/tests/kms_flip.c
index eda2fcc..c2d3929 100644
--- a/tests/kms_flip.c
+++ b/tests/kms_flip.c
@@ -1182,13 +1182,13 @@ static void check_final_state(struct test_output 
*o, struct event_state *es,
         /* Verify we drop no frames, but only if it's not a TV encoder, 
since
          * those use some funny fake timings behind userspace's back. */
         if (o->flags & TEST_CHECK_TS && !analog_tv_connector(o)) {
-               int expected;
+               double expected;
                 int count = es->count;

                 count *= o->seq_step;
-               expected = elapsed / frame_time(o);
-               igt_assert_f(count >= expected * 99/100 && count <= 
expected * 101/100,
-                            "dropped frames, expected %d, counted %d, 
encoder type %d\n",
+               expected = (double)elapsed / frame_time(o);
+               igt_assert_f(fabs((double)count - expected)/expected < 0.01,
+                            "dropped frames, expected %f, counted %d, 
encoder type %d\n",
                              expected, count, 
o->kencoder[0]->encoder_type);
         }
  }

Regards,
Gabriel.

>
>
>>   			     "dropped frames, expected %d, counted %d, encoder type %d\n",
>>   			     expected, count, o->kencoder[0]->encoder_type);
>>   	}
>
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