Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 2617 by [email protected]: cse not working correctly with
powers
http://code.google.com/p/sympy/issues/detail?id=2617
When working with powers and negative numbers cse yields incorrect
expressions. Example code is below (tested on 0.6.7 and 0.7.1). The issue
was also reported to the mailing list.
import sympy
from sympy import *
print('sympy version: %s' % sympy.__version__)
x1=Symbol('x1')
y1=Symbol('y1')
z=Symbol('z', negative=True)
eq=(x1**2/z**2+1/z**2)/z
v1,v2=cse(eq, sympy.numbered_symbols('a'))
print('equation: %s' % eq)
print('cse: %s, formula: %s' % (v1, v2) )
sdict={x1:1,y1:0, z:-1}
yy=eq.subs(sdict)
print('substitution in original: %s' % yy)
v1s=[ (x[0], x[1].subs(sdict)) for x in v1]
xx=v2[0].subs(sdict)
yy=xx.subs(dict(v1s))
print('substitution in cse expression: %s ' % yy)
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