Dear All,
I have a long string and need to search for regular expressions in
there. However it becomes horribly slow as the string length
increases.
Below is an example: when "i" increases by 5, the time spent increases
by more! (my string is 11,000,000 letters long!)
I also noticed that
- the search time increases dramatically with the number of matches found.
- the perl=T option slows down the search
Any idea to speed this up would be greatly appreciated!
Best,
Emmanuel
> for (i in c(10000, 50000, 100000, 500000)){
+ aa = as.character(sample(1:9, i, replace=T))
+ aa = paste(aa, collapse='')
+ print(i)
+ print(system.time(gregexpr("[367]2[1-9][129]",aa)))
+ }
[1] 10000
user system elapsed
0.004 0.000 0.003
[1] 50000
user system elapsed
0.060 0.000 0.061
[1] 1e+05
user system elapsed
0.240 0.000 0.238
[1] 5e+05
user system elapsed
5.733 0.000 5.732
>
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