[NTG-pdftex] [pdftex-Bugs][4290] processing speed: pdftex slows down when processes long files in DVI mode

Bugs item #4290, was opened at 2009-06-26 17:55 Status: Open Priority: 3 Submitted By: The Thanh Han (hanthethanh) Assigned to: Nobody (None) Summary: processing speed: pdftex slows down when processes long files in DVI mode Category: None Group: None Resolution: None Initial Comment: see http://www.ntg.nl/pipermail/ntg-pdftex/2009-May/003786.html ----------------------------------------------------------------------

Comment By: The Thanh Han (hanthethanh) Date: 2009-07-01 19:46

Message: with the help from Taco and Hartmut, the problem has been traced down to this: section 816 from tex the program says: ,-------- | This code assumes that a |glue_node| and a |penalty_node| occupy the | same number of |mem|~words. | @^data structure assumptions@> | | @= | link(temp_head):=link(head); | if is_char_node(tail) then tail_append(new_penalty(inf_penalty)) | else if type(tail)<>glue_node then tail_append(new_penalty(inf_penalty)) | else begin type(tail):=penalty_node; delete_glue_ref(glue_ptr(tail)); | flush_node_list(leader_ptr(tail)); penalty(tail):=inf_penalty; | end; `-------- and synctex has changed glue_node_size to 4, so that when a paragraph is processed, there is one node that was located with size=4 but freed with size=2. Therefore the problem is only visible with very long document like Reinhard's test file. Taco's suggestion for the problem:

I strongly suggest you just change the penalty size to 4, because the other possibilities that I see have much more impact. Starting from the head node each time is quite slow (much slower than the speed penalty incurred by the extra size of the penalty node).

There are other options, but increasing the penalty size is simplest by far. And it is not like a typical paragraph has hundreds of penalties, anyway.

In luatex this worked out reasonably well in the end because in luatex the node list is doubly linked. But in pdftex there is no room for an extra back pointer in the node objects (nor is there in either tex or xetex) so that won't work without a lot of work.

and my response: ,-------- | yes this seems a good option. There is still one catch that | pdftex without synctex still has glue_node_size=2 and | doesn't need this change. Therefore this should better be | done by synctex. `-------- I have sent an email asking synctex's author for this change. ---------------------------------------------------------------------- You can respond by visiting: http://sarovar.org/tracker/?func=detail&atid=493&aid=4290&group_id=106