Status: Accepted Owner: ---- Labels: Type-Defect Priority-Medium New issue 1400 by ondrej.certik: make cse optionally not to generate subexpressions that are only used once http://code.google.com/p/sympy/issues/detail?id=1400
Example: In [1]: a1, a2, a3, a4, a5, a6 = symbols(["a1", "a2", "a3", "a4", "a5", "a6"]) In [2]: result = sqrt((a1-a4)**2 + (a2-a5)**2 + (a3-a6)**2) In [3]: grad = [diff(result, s) for s in (a1, a2, a3, a4, a5, a6)] In [5]: output = [result] + grad In [7]: cse(output) Out[7]: ⎛⎡ ⎛ 2⎞ ⎛ 2⎞ ⎛ 2⎞ ⎜⎢(x₀, a₁ - a₄), (x₁, a₃ - a₆), ⎝x₂, x₁ ⎠, ⎝x₃, x₀ ⎠, (x₄, a₂ - a₅), ⎝x₅, x₄ ⎠ ⎜⎢ ⎝⎣ ⎛ 1 ⎞⎤ ⎡1 , (x₆, x₂ + x₃ + x₅), ⎜x₇, ──────⎟⎥, ⎢──, x₀⋅x₇, x₄⋅x₇, x₁⋅x₇, x₇⋅(a₄ - a₁), x ⎜ ⎽⎽⎽⎽⎟⎥ ⎣x₇ ⎝ ╲╱ x₆ ⎠⎦ ⎤⎞ ₇⋅(a₅ - a₂), x₇⋅(a₆ - a₃)⎥⎟ ⎦⎟ ⎠ The x2, x3 and x5 are only used once. So there should be a parameter to cse() that would optionally make cse return something like: ( [ (x0, a1 - a4), (x1, a3 - a6), (x3, a2 - a5), (x7, (x1**2 + x3**2 + x0***2)**(-1/2)) ], [ 1/x7, x0*x7, x3*x7, x1*x7, x7*(a4 - a1), x7*(a5 - a2), x7*(a6 - a3) ] ) -- You received this message because you are listed in the owner or CC fields of this issue, or because you starred this issue. You may adjust your issue notification preferences at: http://code.google.com/hosting/settings --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy-issues" group. To post to this group, send email to sympy-issues@googlegroups.com To unsubscribe from this group, send email to sympy-issues+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sympy-issues?hl=en -~----------~----~----~----~------~----~------~--~---