[Gzz-commits] manuscripts/Sigs birthday.py

[Tuomas J. Lukka]

CVSROOT:        /cvsroot/gzz
Module name:    manuscripts
Changes by:     Tuomas J. Lukka <address@hidden>        03/05/19 15:58:25

Modified files:
        Sigs           : birthday.py 

Log message:
        drive out numerical inaccuracy

CVSWeb URLs:
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/manuscripts/Sigs/birthday.py.diff?tr1=1.3&tr2=1.4&r1=text&r2=text

Patches:
Index: manuscripts/Sigs/birthday.py
diff -u manuscripts/Sigs/birthday.py:1.3 manuscripts/Sigs/birthday.py:1.4
--- manuscripts/Sigs/birthday.py:1.3    Mon May 19 15:52:24 2003
+++ manuscripts/Sigs/birthday.py        Mon May 19 15:58:25 2003
@@ -4,10 +4,8 @@
     """return log2(p(k balls thrown to n bins, all end up alone))
     """
     return (
-           (n+.5) * log(n) 
-           - (n-k+.5) * log(n-k) 
+           (n-k+.5) * (log(n) - log(n-k))
            - k
-           - k * log(n)
            ) / log(2)
 
 print log2birthdayprob(41, 31)
@@ -15,3 +13,8 @@
 print log2birthdayprob(41, 11)
 print log2birthdayprob(41, 2)
 print log2birthdayprob(2L**56, 2L**23)
+
+for k in [20, 23]:
+    for n in [56, 60]:
+       print n,k,log2birthdayprob(2L**n,2L**k)
+