Jump functions for Xorshift family

[GregPlowman]

From http://xoroshiro.di.unimi.it

All generators, being based on linear recurrences, provide jump functions that make it possible to simulate any number of calls to the next-state function in constant time, once a suitable jump polynomial has been computed. We provide ready-made jump functions for a number of calls equal to the square root of the period, to make it easy generating non-overlapping sequences for parallel computations.

Would it be possible to implement jump functions in this package?
This seems like a nice addition for parallel usage.

[sunoru]

Thanks for the suggestion. I will look into how to implement jump functions for Xorshift family. Maybe you can also have a look at the advance! functions provided by PCG family.

[kafisatz]

http://xoshiro.di.unimi.it/xoroshiro128plus.c

how about this (which I have not tested):

function jump!(r::RandomNumbers.Xorshifts.AbstractXoroshiro128) 
	#static const uint64_t JUMP[] = { 0xdf900294d8f554a5, 0x170865df4b3201fc };
	s0 = UInt64(0)
    s1 = UInt64(0)
    for i=0:1
        #for(int i = 0; i < sizeof JUMP / sizeof *JUMP; i++)
        if i==0
            v=0xdf900294d8f554a5
        else 
            v=0x170865df4b3201fc
        end
		for b=0:64-1
            if !(iszero(v & UInt64(1) << b)) #(JUMP[i] & UINT64_C(1) << b)
                #Bitwise exclusive OR and assignment operator.	C ^= 2 is same as C = C ^ 2
				@inbounds s0=xor(s0,r.x) #s0 ^= s[0]; #s0=s0^s[0]
				@inbounds s1=xor(s1,r.y) #s1 ^= s[1]; #s1=s1^s[1]
            end
			RandomNumbers.Xorshifts.xorshift_next(r)
		end
        r.x = s0;
        r.y = s1;
    end
nothing
end