Here are my timings for sorting a 600 Mb file after giving "sort" one Gigabyte of memory and a very large workspace. It used about 800 Mb of disc workspace and didn't make a dent in the memory. The unsorted file is random order but I also reverse sorted it to be sure that the test is representative.
This test server is nothing special - a 10 year old HP 9000 with HP-UX 11i and slowish 36Gb 10k rpm discs.
Are you sure that you file is only 200 Mb ?
Last edited by methyl; 02-08-2011 at 08:56 AM..
Reason: paste errors
After my previous thread, I think I found out what causes the long delays.
I run this program on several Linux computers, and the sometimes (after the file with the arrays becomes big) the fwrite takes between 100 ms to 900 ms.
This is very bad for me, as I want a timer to halt each 30 ms.... ... (5 Replies)
Hello,
I have a C program that takes anywhere from 5 to 100 arguments and I'd like to run it from a script that makes sure it doesnt take too long to execute. If the C program takes more than 5 seconds to execute, i would like the shell script to kill it and return a short message to the user. ... (3 Replies)
Hi all,
I wrote this shell script to validate filed numbers for input file. But it take forever to complete validation on a file. The average speed is like 9mins/MB.
Can anyone tell me how to improve the performance of a shell script?
Thanks (12 Replies)
Hi,
I am trying to login using ssh on Red Hat Linux 5 server,
The password appears immediately but after I enter the password it takes about 90 seconds to login completely.
Please suggest what changes require?
Regards,
Manoj (4 Replies)
Hello,
like the title says, how can i measure the time it takes to load a module in Linux, and how how can i measure the time it takes to load a statically compiled module.
/Best Regards Olle
---------- Post updated at 01:13 PM ---------- Previous update was at 11:54 AM ----------
For... (0 Replies)
We are running unix. After a reboot of the server we have found that changing password takes a long time. if type in passwd "username" you can type in the 1st instance of the password , press enter , then it will wait for about 3 minutes before bringing up the confirm password line typing it in... (4 Replies)
Hi,
we currently having a issue where when we send jobs to the server for the application lawson, it is taking a very long time to complete. here are the last few lines of the database log.
2012-09-18-10.35.55.707279-240 E244403536A576 LEVEL: Warning
PID : 950492 ... (1 Reply)
Hi,
I wish to check the return value for wget $url.
However, some urls are designed to take 45 minutes or more to return.
All i need to check if the URL can be reached or not using wget.
How can i get wget to return the value in a few seconds ? (8 Replies)
Hi,
I am trying to search for a Directory called "mont" under a directory path "/opt/app/var/dumps"
Although "mont" is in the very parent directory called "dumps" i.e "/opt/app/var/dumps/mont" and it can never be inside any Sub-Directory of "dumps"; my below find command which also checks... (5 Replies)
It takes 6 hrs for a 90 GB zip file that i am copying / transferring from serverA onto serverB.
scp user1@serverA:/opt/setup/cash.zip .
Output:
cash.zip 21% 19GB 4.7MB/s 4:11:46 ETA
uname -a
SunOS serverB 5.11 11.2 sun4v sparc sun4vCan you please suggest if i could do... (11 Replies)
Discussion started by: mohtashims
11 Replies
LEARN ABOUT OSX
sort
sort(3pm) Perl Programmers Reference Guide sort(3pm)NAME
sort - perl pragma to control sort() behaviour
SYNOPSIS
use sort 'stable'; # guarantee stability
use sort '_quicksort'; # use a quicksort algorithm
use sort '_mergesort'; # use a mergesort algorithm
use sort 'defaults'; # revert to default behavior
no sort 'stable'; # stability not important
use sort '_qsort'; # alias for quicksort
my $current;
BEGIN {
$current = sort::current(); # identify prevailing algorithm
}
DESCRIPTION
With the "sort" pragma you can control the behaviour of the builtin "sort()" function.
In Perl versions 5.6 and earlier the quicksort algorithm was used to implement "sort()", but in Perl 5.8 a mergesort algorithm was also
made available, mainly to guarantee worst case O(N log N) behaviour: the worst case of quicksort is O(N**2). In Perl 5.8 and later,
quicksort defends against quadratic behaviour by shuffling large arrays before sorting.
A stable sort means that for records that compare equal, the original input ordering is preserved. Mergesort is stable, quicksort is not.
Stability will matter only if elements that compare equal can be distinguished in some other way. That means that simple numerical and
lexical sorts do not profit from stability, since equal elements are indistinguishable. However, with a comparison such as
{ substr($a, 0, 3) cmp substr($b, 0, 3) }
stability might matter because elements that compare equal on the first 3 characters may be distinguished based on subsequent characters.
In Perl 5.8 and later, quicksort can be stabilized, but doing so will add overhead, so it should only be done if it matters.
The best algorithm depends on many things. On average, mergesort does fewer comparisons than quicksort, so it may be better when
complicated comparison routines are used. Mergesort also takes advantage of pre-existing order, so it would be favored for using "sort()"
to merge several sorted arrays. On the other hand, quicksort is often faster for small arrays, and on arrays of a few distinct values,
repeated many times. You can force the choice of algorithm with this pragma, but this feels heavy-handed, so the subpragmas beginning with
a "_" may not persist beyond Perl 5.8. The default algorithm is mergesort, which will be stable even if you do not explicitly demand it.
But the stability of the default sort is a side-effect that could change in later versions. If stability is important, be sure to say so
with a
use sort 'stable';
The "no sort" pragma doesn't forbid what follows, it just leaves the choice open. Thus, after
no sort qw(_mergesort stable);
a mergesort, which happens to be stable, will be employed anyway. Note that
no sort "_quicksort";
no sort "_mergesort";
have exactly the same effect, leaving the choice of sort algorithm open.
CAVEATS
As of Perl 5.10, this pragma is lexically scoped and takes effect at compile time. In earlier versions its effect was global and took
effect at run-time; the documentation suggested using "eval()" to change the behaviour:
{ eval 'use sort qw(defaults _quicksort)'; # force quicksort
eval 'no sort "stable"'; # stability not wanted
print sort::current . "
";
@a = sort @b;
eval 'use sort "defaults"'; # clean up, for others
}
{ eval 'use sort qw(defaults stable)'; # force stability
print sort::current . "
";
@c = sort @d;
eval 'use sort "defaults"'; # clean up, for others
}
Such code no longer has the desired effect, for two reasons. Firstly, the use of "eval()" means that the sorting algorithm is not changed
until runtime, by which time it's too late to have any effect. Secondly, "sort::current" is also called at run-time, when in fact the
compile-time value of "sort::current" is the one that matters.
So now this code would be written:
{ use sort qw(defaults _quicksort); # force quicksort
no sort "stable"; # stability not wanted
my $current;
BEGIN { $current = print sort::current; }
print "$current
";
@a = sort @b;
# Pragmas go out of scope at the end of the block
}
{ use sort qw(defaults stable); # force stability
my $current;
BEGIN { $current = print sort::current; }
print "$current
";
@c = sort @d;
}
perl v5.16.2 2012-08-26 sort(3pm)