sympy/sympy — pull request #1607 by smichr (2012-10-24 20:57:42+00:00)
Title: 1400: cse removes single-usage reps

I've noticed that expressions still can appear in the cse output that were only used once in the reduced expressions. Now a check is made that indeed they appear more than once.

http://code.google.com/p/sympy/issues/detail?can=2&q=1400