From 2ac5c9f10ad115631dc3ae32916e80e9e20aaa98 Mon Sep 17 00:00:00 2001
From: Jonathan Li <jonathanliworld@gmail.com>
Date: Thu, 15 Mar 2018 14:02:48 -0400
Subject: [PATCH] Added a calculate PI function

I added a calculate pi function. I used the Chudnovsky algorithm
---
 primelib/primelib.py | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/primelib/primelib.py b/primelib/primelib.py
index 70bde8a3982..a284d7f3c22 100644
--- a/primelib/primelib.py
+++ b/primelib/primelib.py
@@ -38,6 +38,25 @@
 goldbach(number)  // Goldbach's assumption
 
 """
+def pi(maxK=70, prec=1008, disp=1007):
+    """
+    maxK: nuber of iterations
+    prec: precision of decimal places
+    disp: number of decimal places shown
+    """
+    from decimal import Decimal as Dec, getcontext as gc
+    gc().prec = prec
+    K, M, L, X, S = 6, 1, 13591409, 1, 13591409 
+    for k in range(1, maxK+1):
+        M = Dec((K**3 - (K<<4)) * M / k**3)
+        L += 545140134
+        X *= -262537412640768000
+        S += Dec(M * L) / X
+        K += 12
+    pi = 426880 * Dec(10005).sqrt() / S
+    pi = Dec(str(pi)[:disp])
+    return pi
+
 
 def isPrime(number):
     """
@@ -602,4 +621,4 @@ def fib(n):
         ans += fib1
         fib1 = tmp
         
-    return ans
\ No newline at end of file
+    return ans