Virtual Programming Laboratory
Frequently Asked Questions
Question: My problem is that the "File Contents" get truncated. Here is what happened:
1) I add few lines at the end of the file.
2) Save the file and close the editor window.
Then, if I edit the file again (or view it from the directory manager) the lines I just added are missing. In any case I even renamed the file but the problem persisted. What should I do?
Answer: VPL text editor's original 8 KB limit was increased, and it currently supports files of up to 64 KB. Larger files are truncated. Be aware!
Question: I try to access VPL, but nothing shows up in the screen. What do I need to do?
Answer: You should use Netscape 4.0 (or newer versions with AWT) supporting both Java and JavaScript. Otherwise, all or some things will not show up.
Question: Although the Lab window is closed, VPL says it is open, and then rejects openning it. Sometime a similar situation happens for closed windows. Help?
Answer: You should always use the supplied "open/close" buttons in order to open or close VPL windows. Otherwise, the state of the window may stay as locked and appears to be in an inconsistent state.
Question: I have just noticed that the problem with some files not being correctly displayed int the File Manager's "Current File View" is connected to "<" and ">" characters. E.g., lines like #include <xyz.h> have problems while lines like #include "xyz.h" are fine. Apart from that, the first line in my program that has a "<" is the first line to have a problem. Any idea why that might be?
Answer: This problem will be fixed in future releases.
Answer: A bug in the program has caused the files being not shown in the directory manager, although they are actually there. VPL does whatever you ask for. If you have deleted a file, you may try going into the cache of your browser (usually in ~/.netscape/cache) and see if a copy of it still exists in there.
Question: I am getting "Error: Socket not connected" error.
Answer: The server is probably dead, let us know and we will be happy to restart it.
Question: I am getting the following error when I try to use VPL:
Error: HTTPd/CGI: could not fork new process, errno is 35.
Answer: Sometimes run-away processes accumulate and make the system unusable. Let us know, so that we can clean it up. Please be patient while we do that.
Question: It seems like running jobs using VPL takes more time than running jobs directly from my UNIX account. Why is that?
Answer: Because VPL copies the executable files to /tmp first in accordance with the system use policy, before starting the execution. You should, too, observe the same system policy :
/tmp is available for use for TEMPORARY files. Please use it when doing IO intensive work.
WARNING: If you run an MPI-based job, you MUST make that code local to each osprey (SunUltra) by copying it to the /tmp of each osprey and run it there. If you VIOLATE this policy, YOU LOSE ACCESS TO The Cluster. Repeat: you will lose your access if violate this policy.
Question: I am submitting jobs using VPL, yet getting the results takes much longer time than it used to take. Why?
Answer: The problem apparently was too many processes got started but never terminated or it didn't terminate successfully so they just got hung. If we notice that, those processes will be killed and VPL get restarted. If this problem occurs, please don't hesitate to let us know about it immediately.
Make sure you use the correct functions. Also make sure your job terminates successfully. First, check your code (the non-MPI part) to see if it is in a correct order, for example, no infinite loops, etc. You always need to terminate your MPI with MPI_Finalize() ...
Question: I have problems with the text editor. When I compile HPF programs it complains about extra characters at the end of each line in the source program although they are not part of my program. How to handle this?
Answer: The VPL editor is really not an editor in the class of emacs or vi. So when you edit a file and use for example the control commands of emacs to remove/add things, etc. after you save it you will get the file you want and you can view/print with no problem. But, when you did the "save" there was more than just the text that got saved; the editor will also stick a control-M "^M" at the end of every line in the file. Of course, when you compile you will get those weird error messages complaining about those control characters. Fortunately, they don't seem to have any effect on the object file so the program will run ok unless you have some other errors in it. So, the point is when you do the editing you will get more than what you asked for, unseen control characters, and the only way at the moment of avoiding this is to do the boring stuff by editing things off-line and then upload the edited file. The editor has some resemblance with the "script" command which makes a typescript of term session. After exiting the file will have "^M" all over it.
Question: I cannot remove or edit some of the files in my directories. For example, I cannot do anything with the files in the directories that contains program examples. Why?
Answer: These files and examples are not physically present at each user's account but linked to one physical set that is not accessed by the users. So, before editing and saving those examples, FIRST copy them to different files and edit or do whatever you would like to do with those new files.
Question: Where can I find more examples on MPI?
Answer: We will supply more examples as needed. Also you can check other places on the web .
Question: Fortran-wise, what is the difference between fixed and free form programs?
Answer: Fixed form programs dictates certain constraints found on the formatting of older Fortran IV style. The first 6 columns are reserved for special use, programs start from the 7th column, and expand up to 72th column. Free form programs follow the formatting of Fortran 90 programs, basically no restrictions on placement of program.
For problems or more help, contact gcf@npac.syr.edu --or-- saleh@npac.syr.edu