Symbol specialization in auto_optimizer() never took effect.

[philip-paul-mueller]

The dict that was storing all the symbols, known_symbols, was emptied just after its creation. The efect was that the specialization never took effect.

[phschaad]

I'm a bit confused, the change (now) seems to be the exact inverse of what it originally was. While I see that this line should be removed, shouldn't this have no effect on behavior whatsoever since it is effectively a dead (or succeeded) line of code?

[philip-paul-mueller]

I think the difference is because of the following loop (see file dace/transformation/auto/auto_optimize.py, line 650ff).
There on line 653 it is checked if the value v is a sympy.Integer and if so it tries to transform it into a Python int, in case this fails the symbol is ignored (I am not sure why though), and will thus not enter known_symbols.
Therefore known_symbols will only contain Python float and int.

However, if known_symbols is first directly constructed, this transformation is not done, and the "offending" (in the sense of having type sympy.Integer which can not be transformed to int) symbols will remain inside the dict.
While the loop will replace all sympy.Integers that can be transformed to Python int with a corresponding Python int it will not remove the sympy.Integer for which this transformation fails and this probably causes the issues we are seeing.

[BenWeber42]

I agree. Basically, if you only look at these two lines, it would seem that the reset should be removed (as initially proposed):

dace/dace/transformation/auto/auto_optimize.py

Lines 649 to 650 in 6691322

	known_symbols = {s: v for (s, v) in symbols.items() if s in sdfg.free_symbols}
	known_symbols = {}

However, looking at the larger context, it becomes clear that the dict comprehension of the first initialization is a strict super set of the later filtering code:

dace/dace/transformation/auto/auto_optimize.py

Lines 649 to 659 in 6691322

	known_symbols = {s: v for (s, v) in symbols.items() if s in sdfg.free_symbols}
	known_symbols = {}
	for (s, v) in symbols.items():
	if s in sdfg.free_symbols:
	if isinstance(v, (int, float)):
	known_symbols[s] = v
	if isinstance(v, sympy.Integer):
	try:
	known_symbols[s] = int(v)
	except TypeError:
	pass

And this is in line with the doc-string:

dace/dace/transformation/auto/auto_optimize.py

Line 559 in 6691322

:param symbols: Optional dict that maps symbols (str/symbolic) to int/float

So it seems like it's best to initialize empty and remove the redundant dict comprehension.