Revisit rotation conversation to csv. It's way too slow!

[OlafHaag]

The conversion is walking the BVH tree for each frame. But the file already has all the rotation values and it just needs to be filtered.

Maybe the values still need conversion because of rotation order or something else. Should check.
There's definitely much room for performance impovement.

[koya-ken]

After profiling with cProfile, I found that the majority of the time was spent in the search function of bvh.py.

Upon reviewing the processing during execution, I noticed that the patterns of arguments being input were only a few variations of joint definitions, so the same processing seemed to be repeated in most calls.

bvh-toolbox/src/bvhtoolbox/bvh.py

Lines 107 to 122 in 81892e4

	def search(self, *items):
	found_nodes = []
	def check_children(node):
	if len(node.value) >= len(items):
	failed = False
	for index, item in enumerate(items):
	if node.value[index] != item:
	failed = True
	break
	if not failed:
	found_nodes.append(node)
	for child in node:
	check_children(child)
	check_children(self.root)
	return found_nodes

As a result, simply caching this function can significantly improve performance.
The modification only requires adding an import and a decorator.
Please consider applying this fix.

import functools

    @functools.lru_cache(maxsize=None)
    def search(self, *items):
        found_nodes = []

I wanted to use functools.cache, but since the Python version needs to be 3.9 or higher, I used lru_cache(maxsize=None) instead.

https://docs.python.org/3.13/library/functools.html

With this modification, the performance improves as shown below when running the bvh2csv command on the bvh file I have at hand.
The test was performed on the same PC.

Before:

bvh2csv  test.BVH
Converting 1 file...
Processing took: 42.38 seconds

After:

bvh2csv test.BVH
Converting 1 file...
Processing took: 1.43 seconds

The BVH file used for the test has 2130 frames, but the effect becomes more significant as the number of frames increases.

Due to certain circumstances, I cannot upload the BVH file.
However, I believe you can quickly verify the behavior with the files you have on hand.

I am using ChatGPT for the English translation.