Eric Arnold wrote:
I'm using win32 gvim70f. If I use the externan Cygwin grep
grep -i -r vimgrep .
it returns the results in under a second.
:vimgrep vimgrep **
takes about 20 seconds.
Without having looked at the code, let me assume that vimgrep is simply
re-using its regular expression
pattern matching code.
I believe that grep itself has several pattern matching algorithms
built-in. If one is looking for
a straight string, Boyer-Moore is a very good algorithm (it ends up
looking at approx O(N/M)
usually, where N=qty chars in text, M=qty chars in pattern). Regular
expressions will, at best,
usually be about O(N) (worst case is a _lot_ longer).
One can look for multiple words quickly with an Aho-Corasik pattern
matcher. Again, they must
be fixed words, no wildcards, etc.
So, unless Bram installed a lot of pattern matching algorithms into ViM
just to support :vimgrep,
I'm not surprised that grep can be a lot faster. Try both algorithms
with a pattern consisting
of a single (non-magic) character and comparing them.
Another point: :vimgrep is often making a list out of the matches,
thereby incurring memory
management overhead.
Regards,
Chip Campbell
