Commit 3b7919d9 authored by Robert David Graham's avatar Robert David Graham
Browse files

blackrock unshuffle

parent 87159068

src/rand-blackrock.c

+47 −3
Original line number Diff line number Diff line
@@ -206,6 +206,32 @@ fe(unsigned r, uint64_t a, uint64_t b, uint64_t m, uint64_t seed) 
        return a * R + L;

    }

}

static inline uint64_t

unfe(unsigned r, uint64_t a, uint64_t b, uint64_t m, uint64_t seed)

{

    uint64_t L, R;

    unsigned j;

    uint64_t tmp;



    if (r & 1) {

		R = m % a;

		L = m / a;

    } else {

		L = m % a;

		R = m / a;

    }



    for (j=r; j>=1; j--) {

        if (j & 1) {

            tmp = (R - F(j, L, seed)) % a;

        } else {

            tmp = (R - F(j, L, seed)) % b;

        }

        R = L;

        L = tmp;

    }

	return a * R + L;

}



/***************************************************************************

 ***************************************************************************/
@@ -221,6 +247,21 @@ blackrock_shuffle(const struct BlackRock *br, uint64_t m) 
    return c;

}



/***************************************************************************

 ***************************************************************************/

uint64_t

blackrock_unshuffle(const struct BlackRock *br, uint64_t m)

{

    uint64_t c;



    c = unfe(br->rounds, br->a, br->b, m, br->seed);

    while (c >= br->range)

        c = unfe(br->rounds, br->a, br->b,  c, br->seed);



    return c;

}





/***************************************************************************

 ***************************************************************************/

static unsigned
@@ -260,7 +301,7 @@ blackrock_verify(struct BlackRock *br, uint64_t max) 
int

blackrock_selftest()

{

    unsigned i;

    uint64_t i;

    int is_success = 0;

    uint64_t range;
@@ -269,10 +310,13 @@ blackrock_selftest() 
	 */

	{

        struct BlackRock br;

		uint64_t result;

		uint64_t result, result2;

        blackrock_init(&br, 1000, 0);



		result = blackrock_shuffle(&br, 10);

		for (i=0; i<10; i++) {

			result = blackrock_shuffle(&br, i);

			result2 = blackrock_unshuffle(&br, result);

		}



	}