Re: [PATCH v3 2/4] hash: add dynamic polynomial calculation

["Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>]

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Hi Stephen,

On 15/10/2024 23:29, Stephen Hemminger wrote:
> On Fri, 11 Oct 2024 18:17:00 +0000
> Vladimir Medvedkin<vladimir.medvedkin@intel.com>  wrote:
>
>> +
>> +uint32_t
>> +rte_thash_get_rand_poly(uint32_t poly_degree)
>> +{
>> +	uint32_t ret_poly;
>> +
>> +	if (poly_degree > 32)
>> +		return 0;
>> +
>> +	do
>> +		ret_poly = __thash_get_rand_poly(poly_degree);
>> +	while (thash_test_poly_order(ret_poly, poly_degree));
> Unbounded loop adds some risk, should there be an upper limit on retries.

Thisis the probabilisticpartof the algorithm.

__thash_get_rand_poly() returns a random polynomial that either 
satisfies the order criteria (element <x> of the field must generate 
multiplicative subgroup of order not less than some number), or not. The 
probability that it does not meet this criteria is strictly less than 1. 
Thus, with each attempt, the probability of not finding suitable 
polynomial exponentially tends to zero.

>
>> +
>> +	return ret_poly;
>> +}
>> diff --git a/lib/hash/version.map b/lib/hash/version.map
>> index 4f13f1d5aa..7ce6ab1121 100644
>> --- a/lib/hash/version.map
>> +++ b/lib/hash/version.map
>> @@ -61,4 +61,5 @@ INTERNAL {
>>   
>>   	rte_thash_gfni_stub;
>>   	rte_thash_gfni_bulk_stub;
>> +	rte_thash_get_rand_poly;
> Why does this function need to be moved to its own file?
> Only used in one place in rte_thash.c.
It was done just for convenience. If you insist, I'll move it to rte_thash.c

-- 
Regards,
Vladimir

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