gmpy_cffi is slow
As you can see, the time taken to initialize an mpz instance is about 10x slower under gmpy_cffi when compared to gmpy.
The gmpy mpz initialisation code uses the CPython internals to access the raw bits storing the value of a python integer (or long). In comparison, gmpy_cffi converts the number to a hex string and then uses mpz_set_str with base 16 to set the GMP mpz value
def _pyint_to_mpz(n, a): """ Set `a` from `n`. :type n: int,long :type a: mpz_t """ if -sys.maxsize - 1 <= n <= sys.maxsize: gmp.mpz_set_si(a, n) elif sys.maxsize < n <= MAX_UI: gmp.mpz_set_ui(a, n) else: gmp.mpz_set_str(a, hex(n).rstrip('L').encode('UTF-8'), 0)
I've tried other methods such as using bit twiddling to break the python int into an array of C ints and then using mpz_import, but it was slower than using hex
def _pyint_to_mpz(n, a): """ Set `a` from `n`. :type n: int,long :type a: mpz_t """ neg = n < 0 n = abs(n) tmp = array.array('L') size = tmp.itemsize numb = (8 * size) mask = ~(~0 << numb) while n: v = n & mask n = n >> numb tmp.append(v) addr, count = tmp.buffer_info() gmp.mpz_import(a, count, -1, size, 0, 0, ffi.cast('void *', addr)) if neg: gmp.mpz_neg(a, a)
The conversion from python long to gmp mpz is by far the main reason why initializing mpzs in gmpy_cffi is so slow, but there isn't really an obvious way to improve on this.
Perhaps cffi could provide a fast method for converting python longs to an array of C ints, but I doubt there's a huge demand for that right now.
We're within a factor of 10 of evil low level C hackery. For now that will have to do.