Lee Naish wrote:
> The "J" command seems to have a complexity bug when given a large numeric
> argument, eg 100000J
>
> eg:
>
> % yes | head -100000 > vimtest
> % time vim vimtest
>
> <Joined all lines using 99999J>
>
> 17.2u 0.0s 2:29.74 11.5% 0+0k 0+10232io 0pf+0w
> % yes | head -200000 > vimtest
> % time vim vimtest
>
> <Joined all lines using 199999J>
>
> 68.8u 0.4s 1:41.22 68.3% 0+0k 0+39648io 0pf+0w
>
> ie, doubling the number of lines increased the runtime by a factor of 4
> exactly - seems like there is a O(N^2) component to the algorithm.
This is a known problem. It works like doing J 100000 times. So near
the end you are appending a short line to a very long line, copying
everything into newly allocated memory.
Allocating all the memory at once is a bit complicated. Perhaps an easy
solution would be to join two lines at a time.
> I've checked out a copy under SVN, found the O(N^2) code and hacked up
> a possible fix, but haven't been able to test it because I have some
> shared library problem - I can create vim7/src/vim but when I run it
> (even the original version) I get:
>
> ld.so.1: vim: fatal: libintl.so.3: open failed: No such file or directory
> Killed
Make sure you do "make distclean" before building and check the
configure output for any trouble.
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