Katharine Berry 7defa796fe cover: significantly improve the speed of cover.ParseProfiles ... ParseProfiles currently uses a regex to parse each line. This is not very fast, and can lead to ParseProfiles being excessively slow on certain pathological inputs. This change substantially improves the performance by parsing manually instead. On an input of about 3 GB of data containing about 36 million lines, the time spent in ParseProfiles drops from 72 seconds to 11 seconds, with actual string parsing time dropping from 61 seconds to 2 seconds. Since this change completely changes the parsing, it also adds some tests for ParseProfiles to help ensure the new parsing is correct. A benchmark for parseLine is also included. Here is a comparison of the old regex implementation versus the new manual one: name old time/op new time/op delta ParseLine-12 2.43µs ± 2% 0.05µs ± 8% -97.98% (p=0.000 n=10+9) name old speed new speed delta ParseLine-12 42.5MB/s ± 2% 2103.2MB/s ± 7% +4853.14% (p=0.000 n=10+9) Fixes golang/go#32211 Change-Id: If8f91ecbda776c08243de4e423de4eea55f0082b Reviewed-on: https://go-review.googlesource.com/c/tools/+/179377 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>		2019-10-24 07:44:52 +00:00
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profile_test.go	cover: significantly improve the speed of cover.ParseProfiles	2019-10-24 07:44:52 +00:00
profile.go	cover: significantly improve the speed of cover.ParseProfiles	2019-10-24 07:44:52 +00:00