# Ruby and threads: a VTK example **URL:** \ **Category:** Ruby\ **Created:** [November 9, 2006, 6:09pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404 "2006-11-09T18:09:18Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 9, 2006, 6:09pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/1 "2006-11-09T18:09:18Z")
Hi, There is a ruby wrapper available for vtk which works, more or less, fine. For those who are not familiar with vtk, it is avisualisation library written in c++ and the output is a native window showing some interactive OpenGL graphics. The VTK code usually ends with: iren = Vtk::RenderWindowInteractor.new iren.start() Here is where the problem comes: iren.start() starts a new thread in c++, while, I am trying to run the script in irb and interactively change the objects properties and see the live results in the OpenGL window. Unfortunately, after iren.start() ruby goes to a deep sleep. This is the irb output: > > ?\> iren.Start() which obviously does not let me to enter any more commands unless I close the window: =\> nil > > which is too late for manipulating objects interactively. It is surprising when a multi-threaded c++ library is single-threaded after wrapping to ruby. If this does something have to do with ruby not supporting native threads, perhaps it is a big sacrifice for portability. What is the best way to have irb command line, while also having the graphics rendering window? ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 9, 2006, 6:25pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/2 "2006-11-09T18:25:34Z")
On Fri, 2006-11-10 at 02:09 +0900, Aureliano B. wrote: > Here is where the problem comes: iren.start() starts a new thread in > > =\> nil > > > > > > which is too late for manipulating objects interactively. I don’t have any of this stuff installed, so I’m guessing, but couldn’t you just do e.g.: winthr = Thread.new { iren.Start() } // do whatever else you need to do winthr.kill # or close the window may be better Obviously I don’t know about the concurrency issues but with this being interactive I’d guess it’s not something you’d worry much about. ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 9, 2006, 7:09pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/3 "2006-11-09T19:09:52Z")
On Fri, 2006-11-10 at 02:36 +0900, Aureliano B. wrote: > ?\> winthr = Thread.new { iren.Start() } > > Still no command line. All I want is a command line with access to the > the objects in the running thread. Well, it looks like something in the library is blocking the calling process (and all Ruby’s green threads) completely. If so, it’s probably something you’d have to talk to the binding’s maintainer about. I did just try to install VTK but it barfed horribly on my Linux box so I’m afraid I can’t be much more help. > You do not need to have access to this library, it can be emulated > easily: Assume you want to run a very long process names > VeryLongProcess(). I want a command line when VeryLongProcess() is > running and I want this command line to have acees to all the objects > that VeryLongProcess() has access to them. Assuming you mean ‘process’ in the sense of ‘something happening in Ruby’, then the thread thing I suggested should work. If OTOH I’m missing something and you’re referring to actual processes, then it gets more involved… ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 9, 2006, 6:36pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/4 "2006-11-09T18:36:03Z")
Ross B. wrote: > winthr = Thread.new { iren.Start() } > > // do whatever else you need to do > > winthr.kill # or close the window may be better I get the same thing: ?\> winthr = Thread.new { iren.Start() } Still no command line. All I want is a command line with access to the the objects in the running thread. You do not need to have access to this library, it can be emulated easily: Assume you want to run a very long process names VeryLongProcess(). I want a command line when VeryLongProcess() is running and I want this command line to have acees to all the objects that VeryLongProcess() has access to them. ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 9, 2006, 7:21pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/5 "2006-11-09T19:21:29Z")
Ross, Forget about vtk, put it this way. Save this in a script and run it by irb: i = 1 while 1 puts i end It doesn’t allow you to add any more command lines unless the never-ending while-loop is over. Wrapping this in a thread does not help it too: Thread.new{ i = 1 while 1 puts i end } All I want to do is to have the while loop, and then enter i = 2 in the command line to get 2 printed. ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 9, 2006, 7:51pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/6 "2006-11-09T19:51:59Z")
On Thu, 09 Nov 2006 18:21:38 -0000, Aureliano B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > It doesn’t allow you to add any more command lines unless the > never-ending while-loop is over. True. > Wrapping this in a thread does not help it too: > > Thread.new{ > i = 1 > while 1 > puts i > end > } Apart from the fact that the output makes it difficult to type, that works fine for me, with one small change - you need to declare ‘i’ before you start the thread - otherwise, it’ll be local to the block you run in the thread. So try (rubified a bit): i = 1 Thread.new { loop { puts i } } You’ll get lots of '1’s printed out. If you just jump in and type ‘i = 2’ and hit return, the '1’s become '2’s. Does that not work for you? ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 10, 2006, 3:06pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/7 "2006-11-10T15:06:21Z")
From: Aureliano B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Subject: Re: Ruby and threads: a VTK example Date: Fri, 10 Nov 2006 03:21:38 +0900 Message-ID: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > It doesn’t allow you to add any more command lines unless the > never-ending while-loop is over. Wrapping this in a thread does not help > it too: What is your OS ? If it is Windows, your trouble may depends on console I/O. Console I/O of Win (e.g. to get a conmmand line on IRB) blocks thread-switching of Ruby. # Please see [ruby-talk:223935] also. ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 10, 2006, 6:18pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/8 "2006-11-10T18:18:14Z")
Hidetoshi NAGAI wrote: > > It doesn’t allow you to add any more command lines unless the > > never-ending while-loop is over. Wrapping this in a thread does not help > > it too: > > What is your OS ? > If it is Windows, your trouble may depends on console I/O. > Console I/O of Win (e.g. to get a conmmand line on IRB) > blocks thread-switching of Ruby. > > # Please see [ruby-talk:223935] also. Hidetoshi, The OS is WinXP, I have also tried IRB with eclipse as an external tool with no luck. What Ross described does not work on windows as he has ruby on a linux box. The example you mentioned in runy-talk was done with tk. Is there any ways or doing this in simple dos command prompt (or eclipse)? I expected ruby to me more portable than this! ---
**Author:** ![buendia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/54ee81/32.png) [@buendia](https://www.ruby-forum.com/u/buendia)\ **Post date:** [November 11, 2006, 3:11pm UTC](https://www.ruby-forum.com/t/ruby-and-threads-a-vtk-example/75404/9 "2006-11-11T15:11:26Z")
From: Aureliano B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Subject: Re: Ruby and threads: a VTK example Date: Sat, 11 Nov 2006 02:18:18 +0900 Message-ID: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > The example you mentioned in runy-talk was done > with tk. Is there any ways or doing this in simple dos command prompt > (or eclipse)? I’m sorry, but I have no idea. If I had, I didn’t make irbtkw.rbw.😉 Probably, it requires rewriting IRB::StdioInputMethod#gets. I don’t know how it has to be changed, because I’m not familiar with programing on Windows.