Simplify backend handling in libintmath.py/libmpf.py

Author: skirpichev

mpmath/libmp/backend.py

@@ -26,11 +26,13 @@
     try:
         import gmpy2 as gmpy
         BACKEND = 'gmpy'
-        MPZ = gmpy.mpz
-        MPQ = gmpy.mpq
     except ImportError:
         pass
 
+    if gmpy:
+        MPZ = gmpy.mpz
+        MPQ = gmpy.mpq
+
 MPZ_ZERO = MPZ(0)
 MPZ_ONE = MPZ(1)
 MPZ_TWO = MPZ(2)

mpmath/libmp/libintmath.py

@@ -10,7 +10,7 @@
 import sys
 from functools import lru_cache
 
-from .backend import BACKEND, MPZ, MPZ_ONE, MPZ_ZERO, gmpy
+from .backend import MPZ, MPZ_ONE, MPZ_ZERO, gmpy
 
 
 small_trailing = [0] * 256
@@ -73,8 +73,7 @@ def bitcount(n):
     """Calculate bit size of abs(n)."""
     return MPZ(n).bit_length()
 
-if BACKEND == 'gmpy':
-    bitcount = gmpy.bit_length
+if gmpy and hasattr(MPZ, 'bit_scan1'):
     def trailing(n):
         return MPZ(n).bit_scan1() if n else MPZ(0)
 
@@ -146,10 +145,10 @@ def numeral_gmpy(n, base=10, size=0, digits=stddigits):
     bd = numeral(B, base, half, digits).rjust(half, "0")
     return ad + bd
 
-if BACKEND == "gmpy":
+numeral = numeral_python
+
+if gmpy:
     numeral = numeral_gmpy
-else:
-    numeral = numeral_python
 
 _1_800 = 1<<800
 _1_600 = 1<<600
@@ -257,7 +256,7 @@ def sqrt_fixed(x, prec):
 
 sqrt_fixed2 = sqrt_fixed
 
-if BACKEND == 'gmpy':
+if gmpy:
     isqrt_small = isqrt_fast = isqrt = gmpy.isqrt
     sqrtrem = gmpy.isqrt_rem
 else:
@@ -270,10 +269,8 @@ def sqrt_fixed(x, prec):
     sqrtrem = sqrtrem_python
     _gcd2 = math.gcd
 
-
-if BACKEND == 'python':
-    gcd = math.gcd
-elif BACKEND == 'gmpy':
+gcd = math.gcd
+if gmpy:
     gcd = gmpy.gcd
 
 
@@ -318,13 +315,12 @@ def ifac2(n, memo_pair=[{0:1}, {1:1}]):
             memo[k] = p
     return p
 ifac2_python = ifac2
+ifac = math.factorial
 
-if BACKEND == 'gmpy':
+if gmpy:
     ifac = gmpy.fac
     ifac2 = gmpy.double_fac
     ifib = gmpy.fib
-else:
-    ifac = math.factorial
 
 ifac = lru_cache(maxsize=1024)(ifac)
 
@@ -386,7 +382,7 @@ def test(a):
     return True
 isprime_python = isprime
 
-if BACKEND == 'gmpy':
+if gmpy and hasattr(gmpy, 'is_prime'):
     isprime = gmpy.is_prime
 
 def moebius(n):

mpmath/libmp/libmpf.py

@@ -186,7 +186,7 @@ def _normalize(sign, man, exp, bc, prec, rnd):
 
 _exp_types = (int,)
 
-if BACKEND == 'gmpy':
+if gmpy:
     _normalize = gmpy._mpmath_normalize
 
 def normalize(sign, man, exp, bc, prec, rnd):
@@ -234,7 +234,7 @@ def from_man_exp(man, exp, prec=0, rnd=round_fast):
 
 int_cache = dict((n, from_man_exp(n, 0)) for n in range(-10, 257))
 
-if BACKEND == 'gmpy':
+if gmpy:
     from_man_exp = gmpy._mpmath_create
 
 def from_int(n, prec=0, rnd=round_fast):
@@ -804,11 +804,10 @@ def python_mpf_mul_int(s, n, prec, rnd=round_fast):
     bc += man>>bc
     return normalize(sign, man, exp, bc, prec, rnd)
 
+mpf_mul_int = python_mpf_mul_int
 
-if BACKEND == 'gmpy':
+if gmpy:
     mpf_mul_int = gmpy_mpf_mul_int
-else:
-    mpf_mul_int = python_mpf_mul_int
 
 def mpf_shift(s, n):
     """Quickly multiply the raw mpf s by 2**n without rounding."""