During the execution of object-oriented applications, several millions of objects are created, used and then collected if they are not referenced. Problems appear when objects are unused but cannot be garbage-collected because they are still referenced from other objects. This is an issue because those objects waste primary memory and applications use more primary memory than they actually need.

Relying on the operating system’s (OS) virtual memory is not always enough since it cannot take into account the domain and structure of applications. At the same time, applications have no easy way to parametrize nor cooperate with memory management.

In our latest paper published in JOT, we present Marea, an efficient application-level object graph swapper for object-oriented programming languages. Its main goal is to offer the programmer a novel solution to handle application-level memory. Developers can instruct our system to release primary memory by swapping out unused yet referenced objects to secondary memory. Our approach has been qualitatively and quantitatively validated. Our experiments and benchmarks on real-world applications show that Marea can reduce the memory footprint between 23% and 36%.

While working on robots, we needed to work with a sensor that uses a serial communication protocol. However, we also needed UDP sockets to work with other parts of the robot. The problem is:

  • SerialPlugin only work in squeak VM (old VM) and not in the Cog VM
  • UDP sockets only work in Cog VM and not in squeak VM

I decided to take the bull by the horns and modify the Cog VM so that the SerialPlugin works. In this post, I will quickly explain what I did.

1. Get the VM sources

git clone git://gitorious.org/cogvm/blessed.git

I cloned the git repository of Cog. I did not used the svn repository (http://squeakvm.org/svn/squeak/trunk) because the git repository also includes useful scripts. Then, I followed the steps described in the HOWTOBUILD file.

2. Create your own VMMaker image

cd image
PHARO_VM=/Applications/SmalltalkVMs/CogVM.app/Contents/MacOS/CogVM ./newImage.sh

You should specify your own VM path. Then, you can use the generator.image that has loaded the right VMMaker package.

3. Generate C source code from Slang

In the generator.image, a workspace contains a lot of useful snippets. Execute the right one depending on your setup. For me it was:

"Configuration for OSX"
CogCocoaIOSConfig new
addExternalPlugins: #( FT2Plugin );
addInternalPlugins: #( UnixOSProcessPlugin );
"generateForDebug;"
generateSources; generate.

You can analyse the generated C source code in the src/ directory.

4. Compile C code

# as of 10.7 llvm is the default but incompatible compiler
export CC='/usr/bin/gcc-4.2'
export MACOSX_DEPLOYMENT_TARGET=10.5
cd build
sh ../codegen-scripts/extract-commit-info.sh
cmake .
make

5. Check your new VM

In the result/ directory you should find your new VM.

6. Modify VM sources

You can now either modify the C source code (plugins, …) or the Slang code. In my case, I changed a single method in the SerialPlugin class. Then I rebuilt a new modified VM and tested it. I also verified that I worked on the latest version.

Note: In my case, I worked on the VMMaker-oscog branch (Pharo branch?) and not the VMMaker.oscog (Eliot’s branch).

7. Publish your patch

I am not sure that I followed the “right” process in this step. What I did is to fill a bug entry in the Cog bug tracker https://code.google.com/p/cog/issues/list and I attached a .mcz (or .st) file to the bug entry.

Thanks to Igor, Esteban and others who made this process simple.

This end of the year comes with good news. Our research on robotic exploration and mapping received a two years funding from the Région Nord-Pas de Calais for a proposal entitled: CAIRE. This project that will be kicked off in 2013 involves two other partners: the RMoD team from INRIA Lille, and the Telice team from the IEMN lab of Lille.

The goal of the CAIRE project is to propose a methodology as well as an infrastructure for developing modular software to control robot for building maps of unknown buildings. One originality of our approach is that we fully rely on dynamic languages and more specifically on the Pharo reflective language. Dynamicity enables fast development and eases debugging. Besides, we rely on reflective and meta-level facilities for building tools and adapting the language to fit our needs.

Research we will be conducting in the CAIRE project will complement our previous work on cooperative exploration of unknown terrain using a fleet of robots. CAIRE is also related to our ongoing project RoboShop which aims at experimenting with robots in a shopping mall. In both projects we are using human size wheeled robots. They also share the same middleware: the de facto standard ROS, from the Open Source Robotics Foundation.

Last october the 29th, Mariano Martinez Peck successufuly  defended his PhD entitled “Application-Level Virtual Memory for Object-Oriented Systems“. The jury agreed on the importance and the quality of the contributions that were published in different journals and conferences. If you are interested learn more, you can find below the slides of the defense, as well as the video recording of Mariano’s talk.

Slides of the PhD Defense

Video of the PhD Presentation

I’m happy to announce the arrival of a new colleague: Dr. Jannik Laval.

Officially, Jannik started working for our team since Friday 2nd november 2012. That was a Pharo sprint day hosted by our partner the RMoD INRIA Lille team. This was the opportunity to revive our dormant project: OCEAN. Luc Fabresse, Jannik Laval and my self are the main contributors of this new network library for Pharo. We worked a on it while Jannik was doing his PhD. An now that he is back, we have new energy to get this project done.

However, the main effort that we all concetrate on is Robotics. With the rest of the CAR team, we target models, software infrastructures and tools to ease the development of control architectures for robots. We expect to produce soon some cool demos.

As a response to a question in the Pharo-dev mailing list, Esteban Lorenzano explains how to make an iOS app that makes use of Pharo. There should be soon a web page on the Pharo web site that summarizes this and provides other details. In the meanwhile, I would like to share with you this solution. Note that Esteban also announced that  in a couple of weeks there will be a jenkins job to build iOS VMs.

Assuming that you already has in your system:

1) Xcode (I’m using version 4.4)
2) CMake (I’m using version 2.8.8)

And assuming also that you already has an iOS development user.
For use pharo in your iPad you need to follow the following steps:

1) clone https://git.gitorious.org/~estebanlm/cogvm/cog-osx.git
2) in ./image dir prepare a VMMaker image (using pharo 1.4):

Gofer it
squeaksource: 'MetacelloRepository';
package: 'ConfigurationOfCog';
load.
(Smaltalk at: #ConfigurationOfCog) project lastVersion load.

3) Generate sources for iPhone:

StackIPhoneConfig new
generateSources; generate.

4) Generate your iPhone image (follow the instructions in iosbuild/resources/README), which is the place where iOS images need to be placed.

5) In dir ./build

build$ ../codegen-scripts/extract-commit-info.sh
build$ cmake -G Xcode .
build$ open iStackVM.image

5.1) you probably need to add your own development profile, the default one is named “iPhone Developer”

6) run

ALTERNATE
To run in Simulator:
Replace in Step 3 from StackIPhoneConfig to StackSimulatorConfig

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On Monday 29th october 2012 at 10am will be held the defense of the PhD of Mariano Martinez-Peck. This work is part of our partnership with  the INRIA RMoD team and proposes Marea an Application-Level Virtual Memory for Object-Oriented Systems. His experiments were obviously made using Pharo and result into  byproducts that are interesting for the community, namely: Fuel fast serializer and Ghost universal proxies.

The defense jury will be composed of:

  • Pr. Christophe Dony, Lirmm, Univ. Montpellier, France (Reviewer)
  • Pr. Robert Hirschfeld, HPI, Postdam, Germany (Reviewer)
  • Dr. Jean-Bernard Stéfani, DR Equipe SARDES, INRIA Grenoble-Rhone-Alpes, France
  • Dr. Roel Wuts, Principal Scientist at IMEC et Professeur à l’universté catholique de Leuven, Belgium
  • Dr. Stéphane Ducasse, DR Equipe RMod, INRIA Lille Nord Europe, France (Director)
  • Dr. Marcus Denker, CR Equipe RMod, INRIA Lille Nord Europe, France (co-supervisor)
  • Dr. Luc Fabresse,  Ecole des Mines de Douai, Université de Lille Nord de France (co-supervisor)
  • Dr. Noury Bouraqadi,  Ecole des Mines de Douai, Université de Lille Nord de France (co-supervisor)

You’ll find below a summary of the thesis:

Application-Level Virtual Memory for Object-Oriented Systems

During the execution of object-oriented applications, several millions of objects are created, used and then collected if they are not referenced. Problems appear when objects are unused but cannot be garbage-collected because they are still referenced from other objects. This is an issue because those objects waste primary memory and applications use more primary memory than what they actually need. We claim that relying on operating systems (OS) virtual memory is not always enough since it is completely transparent to applications. The OS cannot take into account the domain and structure of applications. At the same time, applications have no easy way to control nor influence memory management.

In this dissertation, we present Marea, an efficient application-level virtual memory for object-oriented programming languages. Its main goal is to offer the programmer a novel solution to handle application-level memory. Developers can instruct our system to release primary memory by swapping out unused yet referenced objects to secondary memory.

Marea is designed to: 1) save as much memory as possible i.e., the memory used by its infrastructure is minimal compared to the amount of memory released by swapping out unused objects, 2) minimize the runtime overhead i.e., the swapping process is fast enough to avoid slowing down primary computations of applications, and 3) allow the programmer to control or influence the objects to swap.

Besides describing the model and the algorithms behind Marea, we also present our implementation in the Pharo programming language. Our approach has been qualitatively and quantitatively validated. Our experiments and benchmarks on real-world applications show that Marea can reduce the memory footprint between 25% and 40%

After an experiment with MediaWiki, we chose to switch to WordPress. We prefer this latter because we get quickly a nice look and feel. Even if WordPress is not a wiki, we can still collaboratively fill it with contents. One can easily create and edit pages. The blog part of it eases sharing our team’s news, and other stories about our experiments especially the cool ones with robots. Stay tuned!

Santiago Bragagnolo joined the team since the beginning of the month, as we announced during our talk on Smalltalk for robotics last ESUG conference (see slides below). Santiago is working full time on the RoboShop project where we aim at building an infrastructure for service robotics in the context of a shopping mall. We are using ROS (Robot Operating System) as a middleware. Currently, we are focusing on RoSt a framework to bridge Pharo Smalltalk with ROS. The end of the tunnel is becoming closer. We can call services provided by ROS nodes and we can send ROS topic messages. We are currently making tests with the ROS turtle simulator. We hopefully will soon start experimenting with our human size robots.