Unscientific profiling suggests that my IMP code is spending much of
it time in check code, specifically checking that a particle contains
a given attribute when fetching or setting its value. This check is
not needed in C++ code that is not currently being debugged and it is
extremely hard for the compiler to prove they are not needed. So I
think the right solution is probably to replace the IMP_check in the C+
+ code with an IMP_assert and wrap the methods with python code which
checks that the attribute is there and throws an exception if it is
not. There are probably a few other places like get_particle where
this is also the case, but they don't seem to be bottlenecks at this
point. Any thoughts?