Sponsored Content
Special Forums UNIX and Linux Applications High Performance Computing Massively parallel on single core? Post 302394358 by Andre_Merzky on Thursday 11th of February 2010 07:48:20 AM
Old 02-11-2010
Question Massively parallel on single core?

Hia all,

I am not sure how many people actually follow the HPC forum on unix.com, but you may be interested in discussing the following (academic) problem:

Assume you want to run a *very* large number (say 100.000) of very lightweight synchronous operations. As an example, assume that you want to run 100.000 instances of

Code:
sleep (3600); // thats one hour sleep

The trivial (aka braindead) approach would be

Code:
for ( int i = 0; i < 100000; i++ )
{
  ::sleep (3600);
}

Takes about 15 years to finish ;-)

One could start 1000 threads, and run a sleep in each of them. That reduces the runtime to 100 hours - still 4 days, and the system is totally idle all the time.

So, using more threads? Won't work, as the max-threads-per-process limit will be hit at some point.

So, spawn 100 processes which spawn 1000 threads each?
The max-threads-per-process limit is, on Linux, close to the max-threads-per-system limit, so that won't work. On other Unixes that is different, but I don't think you get 100.000 threads on a normal single CPU system. Do you?

So, what would your approach be?

I am not looking for a sleep replacement: so saying that I should set alarm or something similar is of not much use. Sleep is obviously only an example here - replace it with an extremely lightweight job, like running a very time consuming synchronous remote operation.

I am looking forward to the ideas you guys can come up with! :-)

Cheers, Andre.

Last edited by Andre_Merzky; 02-11-2010 at 08:48 AM.. Reason: layout...
 

9 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

parallel processing

Hi I want to run two shell script files parallely. These two scripts are interacting with the database. can any body help on this Pls Regards Audippa naidu.M (3 Replies)
Discussion started by: audippa
3 Replies

2. UNIX for Dummies Questions & Answers

difference between Dual-core & Core-to-duo

Can anybody tell What is the exact difference between a Dual-core processor and a Core-to-duo processor ?Advance thanks to all my friends. (1 Reply)
Discussion started by: Ajith kumar.G
1 Replies

3. Programming

how to know the application run on which core, and run how many times on this core

I have a dual core pc, I write a application with two child process. I know I can add sched_get_cpu to know the process run on which core, but, it just when the sched_get_cpu is called, it will tell me the result, my quesion is how to know the child proceess spend how many times on one core. (2 Replies)
Discussion started by: yanglei_fage
2 Replies

4. Shell Programming and Scripting

Replace single quote with two single quotes in perl

Hi I want to replace single quote with two single quotes in a perl string. If the string is <It's Simpson's book> It should become <It''s Simpson''s book> (3 Replies)
Discussion started by: DushyantG
3 Replies

5. Shell Programming and Scripting

Multiple lines in a single column to be merged as a single line for a record

Hi, I have a requirement with, No~Dt~Notes 1~2011/08/1~"aaa bbb ccc ddd eee fff ggg hhh" Single column alone got splitted into multiple lines. I require the output as No~Dt~Notes 1~2011/08/1~"aaa<>bbb<>ccc<>ddd<>eee<>fff<>ggg<>hhh" mean to say those new lines to be... (1 Reply)
Discussion started by: Bhuvaneswari
1 Replies

6. Shell Programming and Scripting

For loop in parallel

Hello, My script shell is: for i in $(seq $nb_lignes) do //command java done Please, how can i execute all iteration in parallel ? Thank you so much. (9 Replies)
Discussion started by: chercheur857
9 Replies

7. Shell Programming and Scripting

How to replace file massively?

Hi Gurus, I need to change a large amout of file name's. for example: current file name: file_ABCDE_sufix.txt I need to change them as file_FGHIGHKE_sufix.txt. Is there any way I can change them with script. Thanks in advance (1 Reply)
Discussion started by: ken6503
1 Replies

8. Shell Programming and Scripting

Paste 2 single column files to a single file

Hi, I have 2 csv/txt files with single columns. I am trying to merge them using paste, but its not working.. output3.csv: flowerbomb everlon-jewelry sofft steve-madden dolce-gabbana-watchoutput2.csv: http://www1.abc.com/cms/slp/2/Flowerbomb http://www1.abc.com/cms/slp/2/Everlon-Jewelry... (5 Replies)
Discussion started by: ajayakunuri
5 Replies

9. Shell Programming and Scripting

Python GNU parallel single command on multiple cores

Hello, I have a 4 core machine. Here is my initial script cd /work/ python script.py input.txt output.txt 1 2 3 This script runs for 1.5hrs. So I read across the web and figured out that you can use GNU parallel to submit multiple jobs using parallel. But I am not sure if I can run... (4 Replies)
Discussion started by: jacobs.smith
4 Replies
TAP::Parser::Scheduler(3)				User Contributed Perl Documentation				 TAP::Parser::Scheduler(3)

NAME
TAP::Parser::Scheduler - Schedule tests during parallel testing VERSION
Version 3.28 SYNOPSIS
use TAP::Parser::Scheduler; DESCRIPTION
METHODS
Class Methods "new" my $sched = TAP::Parser::Scheduler->new(tests => @tests); my $sched = TAP::Parser::Scheduler->new( tests => [ ['t/test_name.t','Test Description'], ... ], rules => \%rules, ); Given 'tests' and optional 'rules' as input, returns a new "TAP::Parser::Scheduler" object. Each member of @tests should be either a a test file name, or a two element arrayref, where the first element is a test file name, and the second element is a test description. By default, we'll use the test name as the description. The optional "rules" attribute provides direction on which tests should be run in parallel and which should be run sequentially. If no rule data structure is provided, a default data structure is used which makes every test eligible to be run in parallel: { par => '**' }, The rules data structure is documented more in the next section. Rules data structure The ""rules"" data structure is the the heart of the scheduler. It allows you to express simple rules like "run all tests in sequence" or "run all tests in parallel except these five tests.". However, the rules structure also supports glob-style pattern matching and recursive definitions, so you can also express arbitarily complicated patterns. The rule must only have one top level key: either 'par' for "parallel" or 'seq' for "sequence". Values must be either strings with possible glob-style matching, or arrayrefs of strings or hashrefs which follow this pattern recursively. Every element in an arrayref directly below a 'par' key is eligible to be run in parallel, while vavalues directly below a 'seq' key must be run in sequence. Rules examples Here are some examples: # All tests be run in parallel (the default rule) { par => '**' }, # Run all tests in sequence, except those starting with "p" { par => 't/p*.t' }, # Run all tests in parallel, except those starting with "p" { seq => [ { seq => 't/p*.t' }, { par => '**' }, ], } # Run some startup tests in sequence, then some parallel tests than some # teardown tests in sequence. { seq => [ { seq => 't/startup/*.t' }, { par => ['t/a/*.t','t/b/*.t','t/c/*.t'], } { seq => 't/shutdown/*.t' }, ], }, Rules resolution o By default, all tests are eligible to be run in parallel. Specifying any of your own rules removes this one. o "First match wins". The first rule that matches a test will be the one that applies. o Any test which does not match a rule will be run in sequence at the end of the run. o The existence of a rule does not imply selecting a test. You must still specify the tests to run. o Specifying a rule to allow tests to run in parallel does not make the run in parallel. You still need specify the number of parallel "jobs" in your Harness object. Glob-style pattern matching for rules We implement our own glob-style pattern matching. Here are the patterns it supports: ** is any number of characters, including /, within a pathname * is zero or more characters within a filename/directory name ? is exactly one character within a filename/directory name {foo,bar,baz} is any of foo, bar or baz. is an escape character Instance Methods "get_all" Get a list of all remaining tests. "get_job" Return the next available job as TAP::Parser::Scheduler::Job object or "undef" if none are available. Returns a TAP::Parser::Scheduler::Spinner if the scheduler still has pending jobs but none are available to run right now. "as_string" Return a human readable representation of the scheduling tree. For example: my @tests = (qw{ t/startup/foo.t t/shutdown/foo.t t/a/foo.t t/b/foo.t t/c/foo.t t/d/foo.t }); my $sched = TAP::Parser::Scheduler->new( tests => @tests, rules => { seq => [ { seq => 't/startup/*.t' }, { par => ['t/a/*.t','t/b/*.t','t/c/*.t'] }, { seq => 't/shutdown/*.t' }, ], }, ); Produces: par: seq: par: seq: par: seq: 't/startup/foo.t' par: seq: 't/a/foo.t' seq: 't/b/foo.t' seq: 't/c/foo.t' par: seq: 't/shutdown/foo.t' 't/d/foo.t' POD ERRORS
Hey! The above document had some coding errors, which are explained below: Around line 102: Unknown directive: =over4 Around line 104: '=item' outside of any '=over' perl v5.16.3 2013-05-02 TAP::Parser::Scheduler(3)
All times are GMT -4. The time now is 05:42 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy