Mark Shannon <m...@hotpy.org> added the comment:
This is going in the wrong direction.
Rather than add more complex instructions for use only by pattern matching, we
need to simplify the individual operations and re-use existing instructions.
That way pattern matching can benefit from the general performance improvements
that we are making.
If you are serious about improving the performance of pattern matching, you
need to do the following in the compiler:
1. Generate a decision tree.
2. Improve that decision tree so that fewer decisions are required.
3. Generate bytecode from that tree that uses lower level operations.
E.g.
match x:
case [1]:
A
case [2]:
B
The initial decision tree looks like:
if is_sequence(x):
if len(x) == 1:
if x[0] == 1:
A
if is_sequence(x):
if len(x) == 1:
if x[0] == 2:
B
which can be improved to:
if is_sequence(x):
if len(x) == 1:
if x[0] == 1:
A
elif x[0] == 2:
B
For a sequence of integer constants, introducing the test `type(x) == int` at
the start would allow you to convert the linear sequence of tests into a tree.
Reducing `n` tests to `ln(n) + 1` tests.
----------
nosy: +Mark.Shannon
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44283>
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