Posts Tagged ‘ differences ’

BD-incollo 0.9 is out!

It took me about one year to find some time to enhance my project BD-incollo. I worked hard for 5 days and to add new features and fight the (huge) amount of spam that was wasting my database space. Now I’m very proud to announce bd-incollo 0.9, a free, light, speedy, anonymous Pastebin clone written in Python Django. This version introduces a lot of new features, including the possibility to make diffs between pastes, and fights spam using Akismet. Read more about the features on the project page and on the new News section on the website that makes use of BD-incollo, incollo.com .

BD-incollo 0.9 is free software as always, under the Gnu Affero General Public License 3.

Currently, you can:

  • Copy, Paste and store a text / source code snippet to the system
  • NEW! Give other people the possibility to discover your Paste (make a Paste either public or private)
  • Decide to colorize the syntax of the Paste
  • Share it using its URL
  • NEW! Enhance Pastes! Create a Paste starting from an old one
  • NEW! View differences! Makes use of the powerful diff-match-patch by Neil Fraser to see differences between two Pastes
  • NEW! Antispam protection using Akismet and akismet.py by Michael Foord
  • Download it as plain text
  • View it as plain text
  • Search something interesting through other pastes!
  • Report abuses to site admins

It also uses a very smart hash system that automatically re-computes a hash key in case of collision.

Here is an example of Paste: http://incollo.com/f341e6a4b
Here is an example of enhancement of the Paste: http://incollo.com/ba22929ac
Here is a full-screen diff of the Pastes: http://incollo.com/compare/f341e6a4b/ba22929ac

Play with them! Use incollo.com, spread it!

Road to 1.0

1.0 development will start after my next examination session (on September) and will surely include:

  • Some asynchronous improvements
  • The possibility to teach Akismet about Spam and Ham in Pastes (when admin user is logged in)
  • More cleaner code
  • The possibility to associate a user to its Pastes via a Cookie (always anonymous) and let him delete them
  • Comments to snippets?
  • What else? Contact me if you’ve got ideas!

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2009
07/26
CATEGORY
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Intel Graphic cards, Linux, Xorg and UXA performance boost

For people having Intel graphic chipset under Gnu/Linux, performance using 3D applications or Compiz-* window manager effects has always been a problem. Intel drivers for Xorg never gave problems but have also never been brilliant. I always looked around searching for xorg.conf tuning configuration entries.
Today I was simply browsing Ubuntu Wiki and discovered the UxaTesting page. I wanted to know something about UXA and Intel drivers, so I found a Wikipedia definition:

In computing, UXA is the reimplementation of the EXA graphics acceleration architecture of the X.Org Server developed by Intel. Its major difference with EXA is the use of GEM, replacing Translation Table Maps.

Yeah cool, the official Xorg Wiki Intel Graphics Driver page Gives also some more information, so if you’ve got one of these chipsets (you can verify using lspci | grep VGA ):

  • i810 and variants thereof
  • i815
  • i830M
  • 845G
  • i852GM
  • 855GM
  • 865G
  • 915G and variants (GMA 900)
  • E7221
  • 945G and variants (GMA 950)
  • 946GME
  • G33
  • Q33
  • Q35
  • 965G/Q
  • G35
  • G41
  • G43
  • G/GM/Q45

You may want to try out the new acceleration method by adding this line


Option "AccelMethod" "uxa"

To your /etc/X11/xorg.conf file, in section “Device”.

Please note that:

  1. UXA is not yet stable as EXA. Try it out, signal your experience on the Ubuntu wiki page and fill out a bug if necessary
  2. You will need at least Xorg server 1.6.0
  3. You will need at least xf86-video-intel-2.6.2 drivers
  4. I don’t think this is mandatory, but please tell me if you encounter differences when updating to 2.6.30.x kernel. I already have 2.6.30.0 on Sid so I don’t know if with a previous version this is working

On Debian Sid I just had to add the Option line to my xorg.conf file.
The performance differences are noticeable and incredible. Everything runs faster and smoother.
My glxgears output went from 60 FPS (using EXA) to 425 FPS (using UXA).
This is a 700% performance improvement!

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2009
06/21
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Heap vs. Stack in C++

After the study of pointers versus references, the second natural question that comes in head of a ex Java developer turning to C++ is:

“What are the difference between static and dynamic memory allocation in C++?”

which can be translated as:

“When should I use the stack and when do I have to use the heap in C++?”

that can be further simplified to:

“When should I use the new operator in C++?”

I could simply summarize the answer to: “Use stack when possible”, but I think that this time there is the need of more explanations. Let’s have the following model for a process in the system:

A simplified model for a process

A simplified model for a process

I’m not really interested in an real representation of a process (see Modern Operating Systems by A. S. Tanenbaum for a very good explanation on processes), but focus on the stack and on the heap.
In reality the heap is a software abstraction but you can also imagine it like the stack.
In C++ programs there are also several other memory areas in which objects and non-object values may be stored (see this article on GotW for further details).

Why then choose between stack or heap? Quoting my publication on object-oriented memory management in Java:

Stack-based variables have their extent determined by their scope, so the former is constrained by the structure of the code at compile-time .

Sometimes there is a need for the variables with unconstrained extent in order to cope with
problems where lifetime of a variable can only be known at run-time.
In this case heap-based variables, whose extent is strictly under control of the programmer, are used. [..]

I promise that I will update my 17 pages about OO-memory management to cover also C++ by the end of June. By the way, following some forums, wikipedia, my publication and GotW, I also summarized pros and cons of stack and heap use in C++:

Stack Heap
Its size is determined at compile-time Size determined at run-time
Therefore, it is less expensive and quick Therefore, it is more expensive and slower than stack
The preferred way to store objects and variables if their size is limited. To be used only if needed: the amount of memory needed is variable and unknown, and may increase rapidly.
There is an AUTOMATIC CLEANUP of objects when they go out of their scope Objects STAY IN MEMORY even when you don’t use them anymore.
Programmers don’t have to bother to free resources Therefore, programmers HAVE TO CLEAN memory manually. However, all modern OS free the resources when the program exits.

Update 2009-07-03
After 4 months of heavy GUI and Database C++ programming, here are my thoughts: if you are planning to write a program with something more than a couple of objects interacting, using associations and therefore, objects as attributes, use the heap. Every serious program, even if not really big, uses heap for object allocation. Just take care to delete the objects when you don’t need them anymore. Objects on the heap are dynamically allocated and it is more comfortable to pass them through other objects using pointers. The use of the heap assures the live of objects even if the method that generated them runs out of scope ( =dies ). If you also plan to write GUIs, solid toolkits like QT recommend the use of heap to create graphical objects.

In some Operating Systems, stack is also very limited while heap is usually not.

Here are listed the sources I used for writing this article:

  • http://www.velocityreviews.com/forums/t278261-stack-vs-heap.html
  • http://www.computing.net/answers/programming/stackheap-c/2293.html
  • http://www.codeguru.com/forum/showthread.php?p=1186307#post1186307
  • http://www.codeguru.com/forum/showthread.php?t=350945
  • http://www.gotw.ca/gotw/009.htm
  • http://en.wikipedia.org/wiki/Process_(computing)#Representation
  • http://bd-things.net/object-oriented-memory-management/

Hope that this article helped you to clearly understand the differences between stack and heap allocation in C++, write me if there are other issues or you need more explanations!

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2009
03/20
CATEGORY
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Reference vs. Pointer

In Software Engineering Project course we need to learn some C++ to develop the project. A question that some programmers have when passing from Java to C++ (like me) is “Which are the differences between pointers and references?“. You can find a lot of answers around developers forum, but I summarized them in the following table. Glad if you found it useful!

Reference Pointer
is an object which IS AN ALIAS for another object is an object that CONTAINS THE ADRRESS IN MEMORY of another object
the preferred way of undirectly access objects you should use it just if you really need it, as it lets you to work in a lower level than a reference does
keeps your code clear the code is less clear but still understandable
it must be initialized when created you don’t have to initialize it when declared
it references to the one object and only that one, therefore you can not modify the address referenced because it contains an address, it can point to many different objects during lifetime. The address can be manipulated
when used, the address is dereferenced without using any particular operator the address must be dereferenced using the * operator

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2009
03/18
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BD-theme 1.0 beta 1 released

I’ve finally found the time to make the necessary fixes and improvements to the theme of my blog.
I decided to not name it a final release just because I could not test it with Internet Explorer 6. I believe that the differences with this beta release and the final one will just be some test with that browser and a better code cleanup :-)
Valid XHTML 1.0 Strict.
Yes, this is the theme you’re actually seeing in the blog.
You can go and download it!

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2008
11/27
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BD-incollo

BD-incollo is a collaborative debugging tool like pastebin but written using Django.
Why did I write another pastebin clone?
Pastebin is (sometimes) slow, and I’m not (yet) interested to categorize pastes or to associate them to a user. Pastebin is free and the code is available, but is a single php file, and not a Django project!
There are already other services there, even written using Django, but no one is free software. BD-incollo IS free software. Well, BD-incollo has been written after those Django pastebin clones, so i could learn from their mistakes and write a better one! Everybody is welcome to grab the code and modify it, or even to submit suggestions!
Report feedbacks, feature requests and bugs on the issue tracker.

Quick Jump:

Features

Download

License

Features

  • Copy, Paste and store a text / source code to the system
  • NEW! Give other people the possibility to discover your Paste (make a Paste either public or private)
  • Decide to colorize the syntax of the Paste
  • Share it using its URL
  • NEW! Enhance Pastes! Create a Paste starting from an old one
  • NEW! View differences! Makes use of the powerful diff-match-patch by Neil Fraser to see differences between two Pastes
  • NEW! Antispam protection using Akismet and akismet.py by Michael Foord
  • Download it as plain text
  • View it as plain text
  • Search something interesting through other pastes!
  • Report abuses to site admins

Interesting Stuffs

  • Fast, really fast!
  • It works well and has nice urls, thanks to Django
  • A very clean interface, a minimalist design that gives space to the code (as it should always be)
  • Compatible with every browser (tested with Internet Explorer 6,7,8, Mozilla Firefox 3, Apple Safari, Google Chrome)
  • Resolution friendly! Liquid design that adapts to every monitor resolution (tests from 1024×768)
  • Developer friendly! Every functionality of BD-incollo can be done with max 2 mouse clicks and without a mouse scroll!
  • Tested with lots of pastes, quite every source code should be perfectly viewed (this does not happen with every pastebin clones I’ve tried)
  • Uses Pygments for code highlighting

Download

License

BD-incollo is released under The Gnu Affero GPL version 3! This is different from the license of the contents of the blog

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program. If not, see < http ://www.gnu.org/licenses/ >.

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2008
09/24
CATEGORY
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