It might be possible to work around this with the optimizations flag,
but I'd say cse should just be updated to treat derivatives as
separate symbols.
Aaron Meurer
On Wed, Jul 30, 2025 at 1:33 AM Jason Moore <moorepa...@gmail.com> wrote:
>
> Hi,
>
> I tried:
>
> In [18]: import sympy as sm
>
> In [19]: a, b, c = sm.symbols('a, b, c')
>
> In [20]: f = sm.Function('f')(a)
>
> In [21]: expr = f + f.diff() - f.diff()/(f + f.diff()) - a*b + (a*b)**2
>
> In [22]: sm.cse(expr)
> Out[22]:
> ([(x0, f(a)), (x1, Derivative(x0, a)), (x2, x0 + x1)],
> [a**2*b**2 - a*b - x1/x2 + x2])
>
> In [23]: sm.cse(expr, ignore=[f.diff()])
> Out[23]:
> ([(x0, f(a)), (x1, Derivative(x0, a)), (x2, x0 + x1)],
> [a**2*b**2 - a*b - x1/x2 + x2])
>
> The outcome I desire is:
>
> ([(x0, f(a)), (x1, Derivative(f(a), a)), (x2, x0 + x1)],
> [a**2*b**2 - a*b - x1/x2 + x2])
>
> or:
>
> ([(x1, Derivative(f(a), a)), (x2, f(a) + x1)],
> [a**2*b**2 - a*b - x1/x2 + x2])
>
> that is, that the functions or derivatives are treated like symbols.
>
> The ignore flag is cse does not seem to do that.
>
> Is there a way to use the pre/post processors in cse to do this?
>
> Jason
> moorepants.info
> +01 530-601-9791
>
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