On Thursday, April 30, 2015 at 2:30:48 AM UTC-7, Eric Gourgoulhon wrote:
>
> Hi,
>
> I've recently faced this surprising appearance of a logarithm (in Sage
> 6.7.beta3 as well as in any older versions I've tried, down to Sage 6.3):
>
> sage: var('y')
> y
> sage: f = function('H', x, y); f
> H(x, y)
> sage: loads(dumps(f))
> -x*log(-x*y + 1)
>
This is probably just a nameclash, since pickling symbolic expressions.
Pickling symbolic expressions rather directly depends on pynac's
serialization, so we're restricted by the limitations that has. Note the
following:
sage: function('sin')(x).diff()
D[0](sin)(x)
sage: loads(dumps(function('sin')(x))).diff()
cos(x)
As you can see, pickling a fresh symbolic function that happens to clash
with an existing one doesn't work properly.
My guess is that the segfaults are probably triggered by some violated
assumptions subsequently.
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