Hi,

The attached patch modifies the ~org-babel-tangle~ function to avoid a
quadratic behavior in the number of blocks tangled to a single file.

Tangling an org buffer with 200 blocks to 5 different files yields a
25 % speedup.


* lisp/ob-tangle.el (org-babel-tangle-collect-blocks): Group
collected blocks by tangled file name.
(org-babel-tangle): Avoid quadratic behavior in number of blocks.

--
Sébastien Miquel