Initialization Functions

The functions for integer arithmetic assume that all integer objects are initialized. You do that by calling the function mpz_init.

Function: void mpz_init (mpz_t integer)

Initialize integer with limb space and set the initial numeric value to 0. Each variable should normally only be initialized once, or at least cleared out (using mpz_clear) between each initialization.

Here is an example of using mpz_init:

{
  mpz_t integ;
  mpz_init (integ);
  ...
  mpz_add (integ, ...);
  ...
  mpz_sub (integ, ...);

  /* Unless the program is about to exit, do ... */
  mpz_clear (integ);
}

As you can see, you can store new values any number of times, once an object is initialized.

Function: void mpz_clear (mpz_t integer)

Free the limb space occupied by integer. Make sure to call this function for all mpz_t variables when you are done with them.

Function: void * _mpz_realloc (mpz_t integer, mp_size_t new_alloc)

Change the limb space allocation to new_alloc limbs. This function is not normally called from user code, but it can be used to give memory back to the heap, or to increase the space of a variable to avoid repeated automatic re-allocation.

Function: void mpz_array_init (mpz_t integer_array[], size_t array_size, mp_size_t fixed_num_bits)

Allocate fixed limb space for all array_size integers in integer_array. The fixed allocation for each integer in the array is enough to store fixed_num_bits. If the fixed space will be insufficient for storing the result of a subsequent calculation, the result is unpredictable.

This function is useful for decreasing the working set for some algorithms that use large integer arrays.

There is no way to de-allocate the storage allocated by this function. Don't call mpz_clear!

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