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(gmp.info)Random State Initialization

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Random State Initialization
===========================

 - Function: void gmp_randinit_default (gmp_randstate_t STATE)
     Initialize STATE with a default algorithm.  This will be a
     compromise between speed and randomness, and is recommended for
     applications with no special requirements.

 - Function: void gmp_randinit_lc_2exp (gmp_randstate_t STATE, mpz_t A,
          unsigned long C, unsigned long M2EXP)
     Initialize STATE with a linear congruential algorithm X = (A*X +
     C) mod 2^M2EXP.

     The low bits of X in this algorithm are not very random.  The least
     significant bit will have a period no more than 2, and the second
     bit no more than 4, etc.  For this reason only the high half of
     each X is actually used.

     When a random number of more than M2EXP/2 bits is to be generated,
     multiple iterations of the recurrence are used and the results
     concatenated.

 - Function: int gmp_randinit_lc_2exp_size (gmp_randstate_t STATE,
          unsigned long SIZE)
     Initialize STATE for a linear congruential algorithm as per
     `gmp_randinit_lc_2exp'.  A, C and M2EXP are selected from a table,
     chosen so that SIZE bits (or more) of each X will be used, ie.
     M2EXP >= SIZE/2.

     If successful the return value is non-zero.  If SIZE is bigger
     than the table data provides then the return value is zero.  The
     maximum SIZE currently supported is 128.

 - Function: void gmp_randinit (gmp_randstate_t STATE,
          gmp_randalg_t ALG, ...)
     *This function is obsolete.*

     Initialize STATE with an algorithm selected by ALG.  The only
     choice is `GMP_RAND_ALG_LC', which is `gmp_randinit_lc_2exp_size'.
     A third parameter of type `unsigned long' is required, this is the
     SIZE for that function.  `GMP_RAND_ALG_DEFAULT' or 0 are the same
     as `GMP_RAND_ALG_LC'.

     `gmp_randinit' sets bits in `gmp_errno' to indicate an error.
     `GMP_ERROR_UNSUPPORTED_ARGUMENT' if ALG is unsupported, or
     `GMP_ERROR_INVALID_ARGUMENT' if the SIZE parameter is too big.

 - Function: void gmp_randclear (gmp_randstate_t STATE)
     Free all memory occupied by STATE.