A-M baby

Task/Lucas-Lehmer-test/Python/lucas-lehmer-test.py

@@ -0,0 +1,36 @@
+from sys import stdout
+from math import sqrt, log
+
+def is_prime ( p ):
+  if p == 2: return True # Lucas-Lehmer test only works on odd primes
+  elif p <= 1 or p % 2 == 0: return False
+  else:
+    for i in range(3, int(sqrt(p))+1, 2 ):
+      if p % i == 0: return False
+    return True
+
+def is_mersenne_prime ( p ):
+  if p == 2:
+    return True
+  else:
+    m_p = ( 1 << p ) - 1
+    s = 4
+    for i in range(3, p+1):
+      s = (s ** 2 - 2) % m_p
+    return s == 0
+
+precision = 20000   # maximum requested number of decimal places of 2 ** MP-1 #
+long_bits_width = precision * log(10, 2)
+upb_prime = int( long_bits_width - 1 ) / 2    # no unsigned #
+upb_count = 45      # find 45 mprimes if int was given enough bits #
+
+print (" Finding Mersenne primes in M[2..%d]:"%upb_prime)
+
+count=0
+for p in range(2, upb_prime+1):
+  if is_prime(p) and is_mersenne_prime(p):
+    print("M%d"%p),
+    stdout.flush()
+    count += 1
+  if count >= upb_count: break
+print