ccode

IMPORTANT: ccode is now defunct. It has been replaced by CodeRunner (see https://github.com/trampgeek/CodeRunner) which offers far more features and functionality.

@version 26 May 2012 @author Richard Lobb, University of Canterbury, New Zealand.

ccode is a Moodle question type that requests students to submit C code to some given specification, e.g. write a function int sqr(int x) that returns its parameter squared. The submission is graded by running a series of testcases of the code in a sandbox, comparing the output with the expected output. If all testcases pass, the question is deemed correct, otherwise it is incorrect. ccode is expected to be run in a special adaptive mode, so the student submits each question repeatedly, until a correct result is obtained. Their mark for the question is then determined by the number of submissions and the per-submission penalty set within Moodle in the usual way.

State of the play

I used ccode with a class of 200 students learning C programming. Over a 6 week period there were around 40 ccode quiz questions attempted by all students, often many times over. So there have been at least 10,000 quiz question submissions. Apart from a couple of minor bugs, the system appears to have performed almost faultlessly. I now declare it stable. So it must be time for me to start hacking it again :)

Processing of a typical ccode quiz question seems not to take much longer than processing of an ordinary Moodle quiz question (e.g. multichoice). We ran two live invigilated 1-hour tests with 100 students in each sitting and 6 questions in each test. The works out to about one submission every 5 seconds. The server was a quad core, but except at start up when everyone logged in was never more than about 25% loaded.

INSTALLATION

A. Install the C/C++ sandbox

ccode uses the sandbox that comes with the Moodle online judge assignment plugin (https://github.com/hit-moodle/moodle-local_onlinejudge), so this must be installed first. Installation under Ubuntu was straightforward; I just followed the install instructions at https://github.com/hit-moodle/moodle-local_onlinejudge/blob/master/README.md

Under RedHat, however, it proved a bit more problematic:

1. pcntl is compiled into PHP on my version of Red Hat (RHEL6), so I had to remove the check to see if it was a loaded extension in /var/www/html/moodle/local/onlinejudge/cli/judged.php by commenting out lines 83 - 85:

    if (!extension\_loaded('pcntl') || !extension\_loaded('posix')) {
        cli\_error('PHP pcntl and posix extension must be installed!');
    }
   

2. I had to install php posix, which in RHEL6 is part of php-devel, with

    sudo yum install php-devel
   

B. Install the pycode plug-in

Pycode is a Python equivalent of ccode, and was developed before it. It defines a set of base classes for programming question plugins, referred to generically as progcode. [The Moodle 2.1 question architecture doesn't allow for the possibility of abstract question types, so to prevent users from instantiating the base types, they are hidden inside pycode. This isn't very satisfactory, but was the suggestion made by Tim Hunt in a forum posting and I can't immediately think of a better solution.]

Installing pycode and the progcode base classes is done by:

    git clone https://github.com/trampgeek/pycode
    sudo mv pycode <moodle\_base>/question/type/

A problem here is that pycode questions will not be usable unless the pypy sandbox is also installed -- see the pycode documentation if you wish to do this. Without the pypy sandbox you won't be able to run pycode questions, but ccode should still work fine.

C. Install the moodle quiz question behaviour.

A special Moodle quiz question behaviour is required for progcode-based question types, called adaptive_adapted_for_progcode. It's available as a GIT repo. Install it by:

    git clone https://github.com/trampgeek/adaptive_adapted\_for\_progcode
    sudo mv adaptive_adapted_for_progcode/ <moodle\_base>/question/behaviour/

D. Install the ccode plug-in

Install (at last) the c-code plug itself by:

    git clone https://github.com/trampgeek/ccode
    sudo mv pycode <moodle\_base>/question/type/

E. Test ccode/progcode in Moodle

• Log in as an administrator
• You should be told there are modules available to update.
• Update them.
• Select Settings > Site administrations > Development > Unit tests
• Run the tests in folder question/type/ccode
• You shouldn't get any errors. If you do, you're in trouble. Panic.