Java中的自动编译，自动运行，自动比较结果

Question

dear all, i am new in Java and at now i am trying to develop an application under Java to do such these things: assumption: there is a file contains source code in Java. let's assume that the file contains a main class (and it's main method with several additional methods) and some inner classes which will be used during the main class running time.

processes:

1. the application which i want to develop (call it as ASIN), will try to compile the source code we have assumed above.
2. after compilation phase is finished. i want the ASIN will allocate some memory space 32 Mb (for instance), and give a maximum running time 2 seconds (for instance).
3. after allocating the memory and the maximum time limit for running, ASIN will try to run the java byte code by using allocated resource (memory 32 Mb) with given maximum time. Then ASIN will record/capture result. if the running byte code is using more than allocated memory, or exceeding the given time limit, ASIN will force to stop the execution. so, the normal case is when the execution finished before the maximum time limit and use less than allocated memory.

can java do thing above? any suggestion what should i do?

regards,

Answer 1

Is this supposed to be a grading system for a programming contest or for exercises in a university course? There might exist open-source systems for that, so google it first if you haven't already. If you have to / want to make one yourself, I'm not sure if Java lets you limit the time spent by a program (but you could, of course, simply kill the program after waiting a certain amount of time), but the memory limit of a java program can be specified with eg -Xmx32m when starting the program with the java command. If this is on a unix system, the simplest solution will probably be to use ulimit to limit both the memory usage and the run time.

In either case, I think you'll have to use Runtime.exec() to launch both the compiler and the program. This will also let you feed input into the process and read the output from the process (although I/O redirection could also be performed to/from files if you launch the program with eg

Runtime.getRuntime().exec("java -Xmx32m Program.class < input.txt > output.txt");

As for the comparison: unless you require an exact match (even in whitespace), the simplest solution is probably to redirect the output to a file and invoke diff with either -b or -w , and possibly --ignore-blank-lines ; if the return code is 0, the output is equal to the solution (except for whitespace differences). On the other hand, if you need interactive grading (the program is supposed to "converse" with the grader) or if the output may be formed in different ways such that there is no unique correct answer, you can't use diff ; the grader must read the process' output stream instead.

Answer 2

I'd do this in shell script rather than java. Would that be an option?

You can do the memory and time limiting using ulimit. If you write a small shell script that does this:

set -e
ulimit -v 32768 # ulimit -v works in 1 kB blocks, so this is 32 MB
ulimit -t 2 # ulimit -t works in seconds
java ProgramUnderTest >output

Then when you run it, it will give itself memory and time limits, and launch java as a subprocess. If the program completes in time (note that the limit is on CPU time, not real time), it will finish with exit status 0; otherwise, it will have some nonzero exit status.

If you want to record how much actual time was used within the limit, run java under time :

time java ProgramUnderTest >output

That will print the total amount of time used after the output.

Compiling the code from a script is also easy, of course - just run javac. Remember to check the exit status to see if the code compiled correctly.