Well, a lot of people seem to be having the same kind of questions across different forums and different problems. Here is a brief list of questions that have been coming up quite frequently over the past few weeks, and some hints on what you should do to solve the issue.
Q. What compilers do we use?
A. The compilers for the different languages are specified when you select the language while submitting the solution. Code compiled on other non-standard compilers cannot be guaranteed to compile on the online judge system.
Q. What are the system specifications?
A. As of now, the specifications of the system on which the judge executes the solutions are :
Operating System : Gentoo Linux
Processor : Quad Core Intel running at 2.33 GHz
Memory : 4 GB of RAM (64 MB guaranteed for each submission)
Storage : 160 GB effective storage using SATA RAID 0 configuration
Network Link : 144 Mbit maximum throughput
Q. I can’t seem to find the compilers being used by Codechef. Can you give me a link?
A. The IDEs / Compilers / Interpreters for some commonly used languages are listed below.
C / C++ : You can use the Dev C++ IDE if you are on windows - http://www.bloodshed.net/dev/devcpp.html
Java : Download the Java Development Kit from the Sun website - http://java.sun.com/javase/downloads/index.jsp
Python : Download the python interpreter from - http://www.python.org/download/
Perl : Download perl from http://www.perl.com/download.csp
Ruby : Download it from http://www.ruby-lang.org/en/downloads/
C# : Download it from http://www.microsoft.com/express/vcsharp/
You can use flags like -O2 in C or C++ to turn on compiler level optimization.
Q. Why does my code compile fine in Turbo C but not on the Codechef Judge?
A. The Codechef Judge uses the GNU compiler collection. Turbo C uses some non-standard headers and as such should not be used. A standards compliant C code written under Turbo C will compile fine on the online judge.
Q. Can I include the file conio.h?
A. No, conio.h is not a standard header file and as such is not available under the GNU compiler collection. Code which includes conio.h will not compile on the online judge.
Q. What should I name the class in a java solution?
A. You should name the class as Main. Failure to do so will result in a compilation error on the online judge system.
Q. Do I need to take the input for all testcases at once before processing it?
A. No, you need not take all the input at once. You can take the input for a particular test case and output the answer and then proceed to the next test case. Program should read from standard input and write into standard output. There is no need to read all data first, compute them all and then print all output. It is recommended to read and write data as simultaneously. Technically, server redirects standard stream to files. You can test you programs in the same way at home.
Q. Can I get the input for which my program failed?
A. Currently it is not possible to get the input for which your program fails. Thinking out corner cases is a part of the fun associated with algorithms 
Q. How do I take input for problems which do not specify a distinct terminating condition or the number of test cases?
A. In cases where the total number of test cases are not specified or some input doesn’t serve as the terminating input, you are expected to take input till an EOF marker is encountered. While testing, you can terminate the input in the command line by pressing the <ctrl> and <z> keys together.
Q. How do I get the execution time of a program in Linux?
A. After compiling the program, say you have the output file with the name ’solution’, then, you can get the execution time by using the command “time ./solution”. The sys and user times are what you should be looking at in the output.
Q. The code runs within the time limit on my system, but I get a TLE on Codechef. Why is that so?
A. TLE stands for Time Limit Exceeded. The configuration of your system might be different from the one we use. You need to optimize your algorithm or come up with a better algorithm.
Q. I can’t even take input or print output within the time limit, let alone processing the input. What should I do?
A. Make sure you have submitted an efficient solution to http://www.codechef.com/problems/INTEST/ and http://www.codechef.com/problems/TEST/ and make sure you read http://blog.codechef.com/2009/02/24/54/
Q. The time limit for the problem is 2 seconds, but some accepted solutions take more time. How is that possible?
A. This can happen if the problem has multiple test case files. The time mentioned in the constraints is per input file. If there are multiple input files, then the total time taken for executing all of them is displayed. For example, if the time constraint for the problem is 2 seconds and there are 8 input files, then your program must take at most 2 seconds for any particular input file, but the total time displayed will be the sum of the execution times for the 8 input files and this may exceed 2 seconds.
Q. Why do I get an error called SIGSEGV?
A. A SIGSEGV is an error(signal) caused by an invalid memory reference or a segmentation fault. You are probably trying to access an array element out of bounds or trying to use too much memory. Some of the other causes of a segmentation fault are : Using uninitialized pointers, dereference of NULL pointers, accessing memory that the program doesn’t own.
Q. Why do I get an error called SIGABRT?
A. A SIGABRT is caused if your program aborted due to a fatal error. This can also be caused if you are using an assert() which fails or an abort().
Q. Why do I get an error called SIGFPE?
A. A SIGFPE is caused by a floating point error. Your program is encountering such an error, probably a division by zero or some similar undefined operation.
Q. Why do I get an error called NZEC?
A. NZEC stands for Non Zero Exit Code. Usually, returning non-zero values from main() will cause this error. It helps telling crash from WA (Wrong Answer) with interpreted languages. Typically this would happen if you omit a return 0; from main() in C. For interpreted languages or Java/C++, this could happen if your program threw an exception which was not caught (e.g. Trying to allocate too much memory in a vector).
If you have any other questions, do post them as a comment and we will try to incorporate them into the FAQ.
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Name : Anton Lunyov Age : 23 yrs Inst/Company : Institute of Applied Mathematics and Mechanics of National Academy of Science of Ukraine Userid : anton_lunyov |
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June 29th, 2009 at 6:19 am
what are the list of c++ header files that i can use?
June 29th, 2009 at 1:41 pm
Check here http://www.cppreference.com/
June 29th, 2009 at 11:09 pm
Hi! Why can I only view the submissions of others for particular problems?
June 29th, 2009 at 11:25 pm
Currently only previous contest problem submissions are available as well as two easy practice problems. We will continue to make solutions to past contests available. Soon we will have a visual indicator showing which problems have solutions available.
Cheers
June 30th, 2009 at 6:26 am
many programs submitted in codechef written in C/C++ include header file
as far as i kno… there’s no such header file in Turbo C compiler ( the one i use)…. please mention which header file is it?
June 30th, 2009 at 7:47 am
Please read the FAQ. Turbo C++ is a non standard compiler. Use gcc if you are on Linux or mingw if you are on Windows. The list of files can be seen at http://www.cppreference.com.
July 3rd, 2009 at 6:17 pm
JAVA
my compilations are correct then why do i get a compile error on submitting. I even made the class name as Main.
July 8th, 2009 at 3:37 pm
Will support for Objective-C be added as one of the languages to submit code in?
July 16th, 2009 at 6:13 am
i am doing in ruby
i am getting Runtime Error: NZEC. even though it Exit code: 0 in my platform.
Why is this?
July 16th, 2009 at 6:34 am
@nitin You might want to go through the sample programs in the help section on the site. http://www.codechef.com/help/
@Frank No plans to do this at the moment. If something comes up, we will let you know.
@Johnes You are probably having some issues with the way you are doing your IO. You might want to check that again.
July 27th, 2009 at 4:25 pm
I am using Turbo c++ IDE …is there any way…i can use this compiler and avoid the runtime error (NZEC) that i am getting, everytime i submit a sulution…
July 28th, 2009 at 1:26 am
No, you need to use a more standards compliant compiler like the GNU compiler collection.
August 6th, 2009 at 8:55 am
How to participate in the August Mini Challenge?
August 7th, 2009 at 1:53 am
You can participate in it in the same way you participate in any of the current contests.
August 8th, 2009 at 11:35 pm
But I can’t find any link to it. Can u help me out?
August 9th, 2009 at 3:18 am
A link will be up soon. You can mail us your queries at admin@codechef.com. Don’t go offtopic on the FAQ’s comment section.
August 15th, 2009 at 9:28 am
Hey people,
Just now I submitted my first program in this site but it said “Compilation Failed” though it compiled fine in my system JDK1.6 . Even I was looking for JDK1.6 option in the drop down provided while submitting it but there was only JDK1.5. Now what should I do?
Thanks !
August 15th, 2009 at 2:00 pm
As of now, it is 1.5 We will upgrade soon.
August 20th, 2009 at 2:45 pm
I had tested my program independently. It was working fine. I had tested for few scenarios including the sample input given in the CEO Ride problem. Only after successfully testing I had submitted it here. It is said that it was failed due to run time error. How can I get more info on this.
Thanks
Maheshwar
August 21st, 2009 at 1:36 am
i have an error received when i submitt my solution to factorial that RUNTIME ERROR NZEC
plz…. try to solve my problem
August 21st, 2009 at 1:44 am
You can get a runtime error because of a variety of reasons. You can get a segfault if you are accessing memory which you are not supposed to. You can get a NZEC if your code does not exit with a return status of 0 etc. Depending on what the error code is, you can debug your code and try finding out what is going wrong and where.
August 26th, 2009 at 1:19 pm
Some Language takes More time of execution then Others for eg compare java and c++ so don’t You think there Should be separate time Limit and judging criteria for these languages because it makes impossible for java programmers like me to compete in your competitions…
August 27th, 2009 at 1:42 am
http://blog.codechef.com/2009/04/01/announcing-time-limits-based-on-programming-language/ This has already been addressed.
September 1st, 2009 at 3:11 am
Please tell me what version of PHP codechef is using and what libraries are being enabled.
Thanks.
September 2nd, 2009 at 4:41 pm
I solving Bibi frog problem in python 2.5 and my code is running perfectly on my system but i am getting runtime error wen i submit the solution…plz help me….
September 4th, 2009 at 4:26 am
Can any one tell me that how to submit the programs procedure … and from where the input file gonna be taken … i dont know which input to use for processing the program and checking out the results
… plz help
September 4th, 2009 at 4:27 am
Can any one tell me that how to submit the programs procedure … and from where the input file gonna be taken … i dont know which input to use for processing the program and checking out the results
… plz help
September 4th, 2009 at 5:25 am
The input is to be taken from stdin and the output should be written to stdout.
September 5th, 2009 at 9:43 am
i have written a code in java. it is running fine on my machine but when i upload it online(code chef) it shows run time error ???
plzz help me
September 6th, 2009 at 10:35 pm
Whether i have to give input for all the test cases once or one by one in each test case.
September 7th, 2009 at 2:36 am
@pulkit Check out http://www.codechef.com/help for a sample solution in Java.
@dinesh Either way is fine.
September 7th, 2009 at 4:36 pm
I’ve error at SIGSEGV. Do you have a program to see the false runtime? I see my code. Seems correct n not out of bounds.
September 8th, 2009 at 2:40 am
A segfault can occur due to a number of reasons other than an array access going out of bounds
September 16th, 2009 at 8:49 am
I m keep on trying submitting my code.. but its either showing incorrect or compile error.. its working with no errors in my compiler.. i m using dev-C++ 4.9.9.2… what should i do to successfully submit my code..
September 16th, 2009 at 11:35 am
What do you mean by Trying to allocate too much memory in a vector?…in java??…
September 16th, 2009 at 5:57 pm
What should the main function for a Scheme submission look like?
September 17th, 2009 at 2:44 am
Please take a look at http://discuss.codechef.com/showthread.php?p=135 for sample solutions in different languages for the problem http://www.codechef.com/problems/TEST.
December 1st, 2009 at 1:33 am
can anyone share the Bash script used to test our programs, i'm using python and my code works perfectly on my machine, but the problem every time is with CodeChef