Re: [Unicon-group] Walk of file directory

[Sergey Logichev]

Jafar,

 

You've provided very interesting version of walk directory algorithm. Communication with active threads' is a great thing!

I have checked your program under Windows 7. I was confused the fact that execution time is negligibly depended on number of concurrent threads. I dug into and discovered that the first operation open(s) takes near ALL execution time! 95% at least. Check it yourself when you slightly edit getdirs():

...

if ( stat(s).mode ? ="d" ) & ( tm := &time, d := open(s) ) then {

      if n=1 then write(s," : ",&time-tm)

...

 

 

So, if first open() is so long then all other enhancements have no sense. Please clarify if I am wrong.

 

Best regards,

Sergey

 

22.01.2015, 00:58, "Jafar Al-Gharaibeh" <to.ja...@gmail.com>:

Here is a slightly tweaked/reformatted version. It now by default auto-detect the number of available cores in the machine and launch twice as many threads.

 

--Jafar

On Wed, Jan 21, 2015 at 12:17 PM, Jafar Al-Gharaibeh <to.ja...@gmail.com> wrote:

David,

 

    I added a threaded solution @ http://rosettacode.org/wiki/Walk_a_directory/Recursively#Icon_and_Unicon 

   Please review/edit as you see fit. (The source file is attached). Combining recursion with thread might not be the best solution for this problem. If I were to put this in real use I'd go with an iterative approach using master/workers model. Anyway, this is a excellent demonstration on how to use threads!. The key features are:

 

   1- How to create threads, limit their numbers, self-load balanced (new threads  are spawned at the time/place where needed. One they are done, they vanish allowing new threads to pop up in new places in the directory structure)

   2- pass data and collect results to/from the threads using the new language features.

 

 

Here is some sample output from my desktop machine (quad-core with mechanical HDD. I will try another machine with an SSD and see if more threads scale better). 

 

the first argument to the program is the target directory. The second is the maximum number of  concurrent threads to use at any given moment. (soft limit! my counters are "unmutexed", so the actual number might deviate). Note that this is different from the actual number of threads used during the run which is reported at the end. The program can create/destroy threads as needed, but cannot  use more than "max" # of threads at any given moment, and again "max" is "soft". :)

 

Cheers,

Jafar

 

c:\proj>tdir c:\ 1

39708 directories in 99867 ms using 1 threads

 

c:\proj>tdir c:\ 4

39708 directories in 62222 ms using 4 threads

 

c:\proj>tdir c:\ 4

39708 directories in 87650 ms using 4 threads

 

c:\proj>tdir c:\ 1

39708 directories in 92525 ms using 1 threads

 

c:\proj>tdir c:\ 4

39708 directories in 95655 ms using 4 threads

 

c:\proj>tdir c:\ 16

39708 directories in 66138 ms using 21 threads

 

c:\proj>tdir c:\ 8

39708 directories in 69307 ms using 8 threads

 

c:\proj>tdir c:\ 4

39708 directories in 70539 ms using 4 threads

 

c:\proj>tdir c:\ 16

39708 directories in 76392 ms using 32 threads

 

 

On Sun, Jan 11, 2015 at 1:25 PM, David Gamey <david.ga...@rogers.com> wrote:

Sergey,

 

I am responsible for much of the Rosetta code contributions (thanks also to Steve, Andrew, Matt, Peter, and about 4 others) and this one in particular dating from 2010. As I recall this was before the multi-threading versions were widely available. I think multi-threading is underrepresented in Rosetta/Unicon.

 

If you come up with a multi-threading version, we should add it to the post as an alternative version.  If you don't feel comfortable doing this, post the code and I can add it.

 

David

 

---

From: Sergey Logichev <slogic...@yandex.ru>
To: Jafar Al-Gharaibeh <to.ja...@gmail.com>
Cc: Unicon group <unicon-group@lists.sourceforge.net>
Sent: Sunday, January 11, 2015 1:16 AM
Subject: Re: [Unicon-group] Walk of file directory

Jafar,

 

Thank you for a whole bundle of advices and suggestions! Threads are worth to try. The thought of search by file attributes is very useful too. Your suggestion about slow I/O partly is right. For UNIX I tried the program on Raspberry Pi with 6 Class microSD as HDD (it's slow, agree). But for Windows it was quite fast HDD. It would be interesting to compare performance of the program on Windows with classic approach based on Win32 _FINDFIRST, _FINDNEXT functions. I have threaded Delphi/Lazarus implementations of this algorithm. Feel that it will be faster but in which degree?

 

Sergey

 

10.01.2015, 21:50, "Jafar Al-Gharaibeh" <to.ja...@gmail.com>:

Sergey,

 

  There are so many things that came to mind when I saw your program.

 

1-  At the end of your email, sourceforge ad says "Go Parallel", Which is not a bad idea for this highly parallel application. 

 

 There is a similar program "wordcount" listed in my dissertation (available on unicon.org) that go through directories and count words in every file using threads (Chapter 7, page 107)

 

2- Unicon open() already supports " pattern matching that would greatly (I believe) speedup your program. For example you can do this:

    L := open("*.icn")

 

   to get a list of all of Unicon source files in the current directory. 

 

  Note: It would be nice if there were a way to tell open() to return files not only based on a pattern, but also on file attribute to allow something like "get me all directories in the current directory", or "get me all read only file". There are a lot of situations where filtering directory names for example is very useful - like this program

 

3- The program on Rosetta Code is not optimized for speed. You can minimize the number of lists created and put() by careful rewriting of the code.

 

4- Depending on how deep the directory tree is, there might be a lot of I/O going on. A slow disk might limit how fast you can go regardless of how optimized your code is.

 

I will share results if get around trying any of these options.

 

Cheers,

Jafar

 

 

On Sat, Jan 10, 2015 at 5:51 AM, Sergey Logichev <slogic...@yandex.ru> wrote:

Hello all!

 

Now I investigate the best approach to get list of files in specified directory and beneath in Unicon.

I found excellent example at rosettacode.org: http://rosettacode.org/wiki/Walk_a_directory/Recursively#Icon_and_Unicon

 

I reconstructed this one to implement matching of filenames to specified pattern (regular _expression_). My program recursively walks a directory and prints appropriate filenames. The same as dir (ls) does. All working fine except performance. If directory has a lot of subdirs the search may took 10-20 seconds before starting output. Could you provide some advices how to enchance the performance?

 

Some notes how to make and use. Unpack content of udir.zip to your local directory. Define which environment you use in env.icn file - uncomment line "$define _UNIX 1" in the case of UNIX. Nothing to do in the case of Windows.

Make udir program:

unicon -c futils.icn

unicon -c options.icn

unicon -c regexp.icn

unicon udir.icn

 

Usage: udir -f<filemask>

for example: udir -f*.icn

shall list of icn files in the current dir and all its subdirectories.

 

Best regards,

Sergey Logichev

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