Re: Too slow readln
On 07/16/2017 10:37 AM, Jon Degenhardt wrote:
There's a good discussion in this thread ("Why GNU grep is fast" by Mike
Haertel):
https://lists.freebsd.org/pipermail/freebsd-current/2010-August/019310.html
--Jon
Another fast GNU utility was on Reddit a month ago:
https://www.reddit.com/r/programming/comments/6gxf02/how_is_gnus_yes_so_fast_xpost_runix/
Ali
Re: Too slow readln
I understand the main problem. dirEntries by default follows symlinks. Without it my first grep works only 28.338s. That really cool!
Re: Too slow readln
On Sunday, 16 July 2017 at 17:37:34 UTC, Jon Degenhardt wrote:
On Sunday, 16 July 2017 at 17:03:27 UTC, unDEFER wrote:
[snip]
How to write in D grep not slower than GNU grep?
GNU grep is pretty fast, it's tough to beat it reading one line
at a time. That's because it can play a bit of a trick and do
the initial match ignoring line boundaries and correct line
boundaries later. There's a good discussion in this thread
("Why GNU grep is fast" by Mike Haertel):
https://lists.freebsd.org/pipermail/freebsd-current/2010-August/019310.html
--Jon
Thank you. I understand yet another trick:
$ find . -exec file -bi {} +
is the same
$ file -bi `find .`
Re: Too slow readln
On Sunday, 16 July 2017 at 17:03:27 UTC, unDEFER wrote:
[snip]
How to write in D grep not slower than GNU grep?
GNU grep is pretty fast, it's tough to beat it reading one line
at a time. That's because it can play a bit of a trick and do the
initial match ignoring line boundaries and correct line
boundaries later. There's a good discussion in this thread ("Why
GNU grep is fast" by Mike Haertel):
https://lists.freebsd.org/pipermail/freebsd-current/2010-August/019310.html
--Jon
Too slow readln
Hello, there!
I have the next "grep" code:
https://dpaste.dzfl.pl/7b7273f96ab2
And I have the directory to run it:
$ time /home/undefer/MyFiles/Projects/TEST/D/grep "HELLO" .
./strace.log: [pid 18365] write(1, "HELLO\n", 6HELLO
real1m17.096s
user0m54.828s
sys 0m13.340s
The same result I get with ldc2..
The same with bash and grep:
$ time for i in `find .`; do file -b "$i" | grep -q text && grep
-a "HELLO" "$i"; done
[pid 18365] write(1, "HELLO\n", 6HELLO
real0m42.461s
user0m23.244s
sys 0m22.300s
Only `file` for all files:
$ time find . -exec file {} + >/dev/null
real0m15.013s
user0m14.556s
sys 0m0.436s
Only grep for all files:
$ for i in `find .`; do file -b "$i" | grep -q text && echo "$i";
done > LIST1
$ time for i in `cat LIST1`; do grep -a "HELLO" "$i"; done
[pid 18365] write(1, "HELLO\n", 6HELLO
real0m4.431s
user0m1.112s
sys 0m3.148s
So 15+4.4 much lesser than 42.46. Why? How "find" so fast can run
"file" so many times?
And why 42.461s much lesser 1m17.096s?
The second version of grep:
https://dpaste.dzfl.pl/9db5bc2f0a26
$ time /home/undefer/MyFiles/Projects/TEST/D/grep2 "HELLO" `cat
LIST1`
./strace.log: [pid 18365] write(1, "HELLO\n", 6HELLO
real0m1.871s
user0m1.824s
sys 0m0.048s
$ time grep -a "HELLO" `cat LIST1`
./strace.log:[pid 18365] write(1, "HELLO\n", 6HELLO
real0m0.075s
user0m0.044s
sys 0m0.028s
The profiler says that readln eats CPU. So why 0m0.075s much
lesser 0m1.871s?
How to write in D grep not slower than GNU grep?
