On Mon, 3 Nov 2025 at 16:47, Ashutosh Chauhan <[email protected]> wrote:
>
> I suggest enhancing SymPy’s numeric evaluation process by adding a step to
> algebraically rewrite expressions into simpler or more numerically stable
> forms before substituting numeric values.
There have been previous proposals around the Herbie algorithm which
is for this. In general a difficulty of using something like this is
that SymPy expressions don't preserve things like the order of
associative operations e.g. there is no distinction between (x + y) +
z and x + (y + z) even though these can be very different for floating
point accuracy.
Note that in your example it is recommended to use
expr.evalf(subs={x:0.1})
rather than
expr.subs({x:0.1}).evalf()
The former is recommended because it is more accurate.
--
Oscar
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