This implements the algorithm qsufsort using the sort package
as a sorting primitive. Its worst-case performance is O(N*log(N)), and it
uses only an additional slice of N ints of memory during creation.
Benchmarks (seconds):
old new
10k nulls 149 0.044
1M English corpus 32.0 3.6
R=gri, gri1
CC=golang-dev
https://golang.org/cl/3752044
Implementation uses fast suffixarray lookup to find
initial matches if the regular expression starts with
a suitable prefix without meta characters.
R=r, rsc
CC=golang-dev
https://golang.org/cl/3720042
This is a replacement for pending CL 2219042. It only contains
the raw suffixarray functionality with two methods:
- New create a new index from some data
- Lookup lookup occurences of a bytes slice in the data
Any other functionality (dealing with multiple data sets and
the corresponding position lists) is generic and doesn't have
to be part of this package.
Known performance bug: This implementation works fine for data sets
up to several megabytes as long as it doesn't contain very long
contiguous sequences of equal bytes. For instance, index creation for
all .go files under GOROOT (250KLOCs, approx. 9MB) takes ~50s on
2.66 GHz Intel Xeon as long as test/fixedbugs/257.go is excluded.
With that file, index creation times takes several days. 257.go contains
a string of 1M smiley faces.
There are more sophisticated suffixarray creation algorithms which
can handle very long common prefixes. The implementation can be
updated w/o the need to change the interface.
R=rsc, r, PeterGo
CC=golang-dev
https://golang.org/cl/2265041
