pytorch

1ff52225 - Unify SymIntNode and SymFloatNode into SymNode (#87817)

Unify SymIntNode and SymFloatNode into SymNode (#87817) This refactor was prompted by challenges handling mixed int/float operations in C++. A previous version of this patch added overloads for each permutation of int/float and was unwieldy https://github.com/pytorch/pytorch/pull/87722/ This PR takes a different approach. The general outline of the patch is to combine the C++ types SymIntNode and SymFloatNode into a single type, SymNode. This is type erased; we no longer know statically at C++ if we have an int/float and have to test it with the is_int()/is_float() virtual methods. This has a number of knock on effects. - We no longer have C++ classes to bind to Python. Instead, we take an entirely new approach to our Python API, where we have a SymInt/SymFloat class defined entirely in Python, which hold a SymNode (which corresponds to the C++ SymNode). However, SymNode is not pybind11-bound; instead, it lives as-is in Python, and is wrapped into C++ SymNode using PythonSymNode when it goes into C++. This implies a userland rename. In principle, it is also possible for the canonical implementation of SymNode to be written in C++, and then bound to Python with pybind11 (we have this code, although it is commented out.) However, I did not implement this as we currently have no C++ implementations of SymNode. Because we do return SymInt/SymFloat from C++ bindings, the C++ binding code needs to know how to find these classes. Currently, this is done just by manually importing torch and getting the attributes. - Because SymInt/SymFloat are easy Python wrappers, __sym_dispatch__ now takes SymInt/SymFloat, rather than SymNode, bringing it in line with how __torch_dispatch__ works. Some miscellaneous improvements: - SymInt now has a constructor that takes SymNode. Note that this constructor is ambiguous if you pass in a subclass of SymNode, so an explicit downcast is necessary. This means toSymFloat/toSymInt are no more. This is a mild optimization as it means rvalue reference works automatically. - We uniformly use the caster for c10::SymInt/SymFloat, rather than going the long way via the SymIntNode/SymFloatNode. - Removed some unnecessary toSymInt/toSymFloat calls in normalize_* functions, pretty sure this doesn't do anything. - guard_int is now a free function, since to guard on an int you cannot assume the method exists. A function can handle both int and SymInt inputs. - We clean up the magic method definition code for SymInt/SymFloat/SymNode. ONLY the user classes (SymInt/SymFloat) get magic methods; SymNode gets plain methods; this is to help avoid confusion between the two types. Signed-off-by: Edward Z. Yang <ezyang@fb.com> cc @jansel @mlazos @soumith @voznesenskym @yanboliang @penguinwu @anijain2305 Pull Request resolved: https://github.com/pytorch/pytorch/pull/87817 Approved by: https://github.com/albanD, https://github.com/anjali411