Right! Ok. Yes, that makes a lot more sense. I'm parking my random
vector/matrix stuff because it's clear (to me at least) that
Vector&Matrix need some revamping.
But still, how should a random based on MurmurHash work?
Lance
On Fri, May 20, 2011 at 7:29 PM, Ted Dunning <ted.dunn...@gmail.com> wrote:
> No. I was referring to the specific use of random number generators to
> generate an ephemeral random matrix. I prefer to hash the element location
> in order to generate the element value than to use a random number generator
> seeded by the element location. These are formally equivalent but
> practically quite different since hash functions are often designed with
> fast startup and PRNG's are often designed without much regard to startup or
> reseeding cost. MersenneTwister in particular is a very bad generator with
> respect to the cost of reseeding. Murmurhash is a very good example of a
> lean hash function.
>
> On Fri, May 20, 2011 at 7:25 PM, Lance Norskog (JIRA) <j...@apache.org>wrote:
>
>>
>> Ted, you mentioned wanting a MurmurHash Random class. Is this what you
>> envisioned? (It is not finished code; see below).
>>
>> {code}
>> public class MurmurHashRandom extends Random {
>> private long murmurSeed;
>> private final ByteBuffer buf;
>>
>> public MurmurHashRandom() {
>> this(0);
>> }
>>
>> public MurmurHashRandom(int seed) {
>> SeedGenerator gen = new FastRandomSeedGenerator();
>> byte[] bits = RandomUtils.longSeedtoBytes(gen.generateSeed());
>> buf = ByteBuffer.wrap(bits);
>> this.murmurSeed = MurmurHash.hash64A(bits, seed);
>> }
>>
>> @Override
>> public long nextLong() {
>> long oldSeed = murmurSeed;
>> murmurSeed = MurmurHash.hash64A(buf, (int) murmurSeed);
>> return oldSeed;
>> }
>>
>> {code}
>>
>>
>
--
Lance Norskog
goks...@gmail.com
