# A threaded 'find' library?

**URL:** <https://www.ruby-forum.com/t/a-threaded-find-library/117193>\
**Category:** Ruby\
**Created:** [October 14, 2007, 4:37pm UTC](https://www.ruby-forum.com/t/a-threaded-find-library/117193 "2007-10-14T16:37:13Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![danielb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/c57346/32.png) [@danielb](https://www.ruby-forum.com/u/danielb)\
**Post date:** [October 14, 2007, 4:37pm UTC](https://www.ruby-forum.com/t/a-threaded-find-library/117193/1 "2007-10-14T16:37:13Z")

</div>

Hi all,

The recent talk of threaded access to a file made me wonder if I could  
do the same with a file searching lib (file-find in my case). This is  
the basic logic:

paths.each{ |path|  
Dir.foreach(path){ |file|  
paths \<\< file if file is a directory (and not already searched)  
next unless file matches user-supplied pattern  
}  
}

I thought I setting up a thread queue and spawning a new thread for each  
new directory would speed it up, but my (probably poor) attempts to  
implement it did not result in any speed improvements, and usually  
slowed it down a little bit.

Any suggestions?

Thanks,

Dan

---

<div class="post-metadata">

**Author:** ![danielb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/c57346/32.png) [@danielb](https://www.ruby-forum.com/u/danielb)\
**Post date:** [October 14, 2007, 8:00pm UTC](https://www.ruby-forum.com/t/a-threaded-find-library/117193/2 "2007-10-14T20:00:10Z")

</div>

On 14/10/2007, Daniel B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ```
> }
> 
> ```
> 
> }
> 
> I thought I setting up a thread queue and spawning a new thread for each  
> new directory would speed it up, but my (probably poor) attempts to  
> implement it did not result in any speed improvements, and usually  
> slowed it down a little bit.

That’s because ruby does not really support concurrent threads. Any  
overhead you add by threading only slows things down. And after you  
run the program for the first time you probably have most of the  
directories cached so you cannot cover any waiting for io with threads  
either.

To fake the delay you could put a sleep in front of calling  
Dir.foreach. This is where the directory would be likely opened and  
the filesystem might need to fetch a block or two.

You can also perform a test with a floppy, just unmount, eject, and  
remount it each time to make sure the cache is invalidated 🙂

Thanks

Michal