Re: Indexes for hashes

Crc32 is great because it is supported by Intel Hardware, unfortunatelly
you have to code something like this:

http://stackoverflow.com/questions/31184201/how-to-implement-crc32-taking-advantage-of-intel-specific-instructions

int32_t sse42_crc32(const uint8_t *bytes, size_t len){
uint32_t hash = 0;
size_t i = 0;
for (i=0;i<len;i++) {
hash = _mm_crc32_u8(hash, bytes[i]);
}

return hash;}

It is supported by GCC and will implemented as hardware computing which
really fast.
you can use 64bit integer to have more precise hashing, so don't worry
about uniformity.

Btw: crc32 is not part of the cryptography, it is part of hashing or
signature.

Regards,

On Fri, Jun 17, 2016 at 3:32 PM, Ivan Voras <ivoras(at)gmail(dot)com> wrote:

> And in any case, there's no crc32 in the built-in pgcrypto module.
>
>
> On 17 June 2016 at 06:18, Claudio Freire <klaussfreire(at)gmail(dot)com> wrote:
>
>> On Fri, Jun 17, 2016 at 1:09 AM, julyanto SUTANDANG
>> <julyanto(at)equnix(dot)co(dot)id> wrote:
>> > This way is doing faster using crc32(data) than hashtext since crc32 is
>> > hardware accelerated in intel (and others perhaps)
>> > this way (crc32) is no way the same as hash, much way faster than
>> others...
>> >
>> > Regards,
>>
>> Sure, but I've had uniformity issues with crc32.
>>
>
>

--

Julyanto SUTANDANG

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