Create comm.py

comm.py

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+import math
+from scipy.stats import binom
+def comm(N,delta,A,P):
+#N is the number of nodes, delta is the failure prob. which can be tolerated, A is the fraction of a committee (typical value is  1/3) and P  is the fraction of adversarial nodes (typical value is 1/4). 
+    K = 1
+    n = N
+    r = 0
+    Prob = 0.0
+    while Prob < delta:
+        K_1 = K
+        n_1 = n
+        r_1 = r
+        Prob_1 = Prob
+        K = K + 1
+        n = N // K
+        r = N % K
+        if 0 < r:
+            Prob_n = binom.cdf(math.floor(A * n), n, P)
+            Prob_n1 = binom.cdf(math.floor(A * (n+1)), n+1, P)
+            Prob = 1 - Prob_n ** (K - r) * Prob_n1 ** r
+        else:
+            Prob_n = binom.cdf(math.floor(A * n), n, P)
+            Prob = 1 - Prob_n ** K
+    #return number of committees, K_1, committee size, n_1, number of committees with size n_1+1, r_1 and prob. of failure, Prob_1. 
+    return K_1, n_1, r_1, Prob_1;