Re: [PATCH i-g-t 4/5] benchmarks/gem_exec_trace: use hars_petruska_f54_1_random() from lib/rand

[Jani Nikula <jani.nikula@intel.com>]

On Mon, 22 Jun 2026, Jani Nikula <jani.nikula@intel.com> wrote:
> On Fri, 19 Jun 2026, Zbigniew Kempczyński <zbigniew.kempczynski@intel.com> wrote:
>> On Thu, Jun 18, 2026 at 05:09:52PM +0300, Jani Nikula wrote:
>>> Remove the local duplicate of hars_petruska_f54_1_random() by switching
>>> to use lib/rand.
>>> 
>>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>> ---
>>>  benchmarks/gem_exec_trace.c | 12 +++---------
>>>  1 file changed, 3 insertions(+), 9 deletions(-)
>>> 
>>> diff --git a/benchmarks/gem_exec_trace.c b/benchmarks/gem_exec_trace.c
>>> index 4263ccb03dbd..c27639105903 100644
>>> --- a/benchmarks/gem_exec_trace.c
>>> +++ b/benchmarks/gem_exec_trace.c
>>> @@ -42,6 +42,7 @@
>>>  #include "drm.h"
>>>  #include "drmtest.h"
>>>  #include "i915/gem_create.h"
>>> +#include "igt_rand.h"
>>>  #include "igt_stats.h"
>>>  #include "intel_io.h"
>>>  #include "ioctl_wrappers.h"
>>> @@ -92,14 +93,7 @@ struct trace_wait {
>>>  	uint32_t handle;
>>>  } __attribute__((packed));
>>>  
>>> -static uint32_t hars_petruska_f54_1_random(void)
>>> -{
>>> -	static uint32_t state = 0x12345678;
>>> -
>>> -#define rol(x,k) ((x << k) | (x >> (32-k)))
>>> -	return state = (state ^ rol (state, 5) ^ rol (state, 24)) + 0x37798849;
>>> -#undef rol
>>> -}
>>> +static uint32_t random_state = 0x12345678;
>>>  
>>>  static double elapsed(const struct timespec *start, const struct timespec *end)
>>>  {
>>> @@ -277,7 +271,7 @@ static double replay(const char *filename, long nop, long range)
>>>  				sizeof(*exec_objects)))->handle = bo[0];
>>>  
>>>  			if (nop > 0) {
>>> -				eb.batch_start_offset = hars_petruska_f54_1_random();
>>> +				eb.batch_start_offset = hars_petruska_f54_1_random(&random_state);
>>
>> With random_state as above this offset is not random. I think adding nop
>> to random_state would do this.
>
> I'm only aiming to do a non-functional conversion to existing library
> functions. Please explain how this patch changes behaviour; I don't see
> it.

Zbigniew, ping?

>
>
> BR,
> Jani.
>
>>
>> --
>> Zbigniew
>>
>>>  				eb.batch_start_offset =
>>>  					((uint64_t)eb.batch_start_offset * range) >> 32;
>>>  				eb.batch_start_offset = ALIGN(eb.batch_start_offset, 64);
>>> -- 
>>> 2.47.3
>>> 

-- 
Jani Nikula, Intel