** Using WeBWorK **

Sometimes, when trying to view problems, users get an error message like the following. If the user reloads the page, the problem is shown correctly. This happens inconsistently, can happen with any problem, including those that have been used for years and we know there is nothing wrong with them. Restarting the server solves the problem temporarily, but within a couple of days this starts happening again.

Any ideas why this could be happening?

Error messages

Can't locate object method "getCopy" via package "Parser::Context" at line 988 of [PG]/macros/PGnumericevaluators.pl Died within main::NUM_CMP called at line 411 of [PG]/macros/PGnumericevaluators.pl from within main::num_cmp called at line 45 of [TMPL]/Library/Rochester/setTrig09Laws/srw6_1_53.pg
Error details

Problem2
ERROR caught by Translator while processing problem file:Library/Rochester/setTrig09Laws/srw6_1_53.pg
****************
Can't locate object method "getCopy" via package "Parser::Context" at line 988 of [PG]/macros/PGnumericevaluators.pl
Died within main::NUM_CMP called at line 411 of [PG]/macros/PGnumericevaluators.pl
from within main::num_cmp called at line 45 of [TMPL]/Library/Rochester/setTrig09Laws/srw6_1_53.pg

Request information
Time Wed Jan 27 14:34:14 2010
Method GET
URI /webwork2/Math5-Nogin/set_01/2/
HTTP Headers
Keep-Alive 300
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
User-Agent Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.11) Gecko/2009061613 CentOS/3.0.11-2.el5.centos Firefox/3.0.11
Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Connection keep-alive
Referer http://webwork2.math.csufresno.edu/webwork2/Math5-Nogin/set_01/1/?effectiveUser=mnogin&displayMode=images&key=qHJmiTg2iVxdpFd9IJCyBWqYPGg9NHhZ&user=mnogin
Accept-Encoding gzip,deflate
Cookie __qca=P0-2132759669-1251736433489; __utma=110011415.2469005800571971600.1251736434.1264451351.1264612528.50; __utmz=110011415.1264612528.50.50.utmcsr=zimmer.csufresno.edu|utmccn=(referral)|utmcmd=referral|utmcct=/~mnogin/; __unam=69a926a-123727f0344-37280b6e-5; cssln116HFR1-84915=6Rv7Lv3J5GdmnQprTM9pqw1TBhzjtPcK!-484220617; csuf_info=Maria Nogin~mnogin@csufresno.edu; csuf_auth=facstaf; https%3a%2f%2fmy.csufresno.edu%2fpsp%2fmfs%2fcsu%2ffresno%2frefresh=list:||||||||||||||||||||||||||||||||||||||||||||||||; PS_TOKEN=AAAAogECAwQAAQAAAAACvAAAAAAAAAAsAARTaGRyAgBOcwgAOAAuADEAMBThC0wHImLFgiDSdcQtXTiY8ihm4gAAAGIABVNkYXRhVnicLYpJCoAwEAQrKh49+I9ITCTRu8tNgl/xez7ONjhD10xBA7ep6gaDpno+9ow4AjNejLLQsnFydGR2LkkW10kFV8q2XCtP/z8oUQyFS9mkeF5zrwtr; ExpirePage=https://my.csufresno.edu/psp/mfs/; __utmc=110011415; cssln113HFR1-84915=rv3dLd1QvBCf1Z7D9WJ7pFCHjzgc2tTn!-168500861; cssln114HFR1-84915=LpvLLg1BlyXTJ0nhn9PzrxQhhfm8KqLT!1321201705; cssln137FFR1-84816=25fQLg0Yy5Rnch3tbHnZbj2pyrhfWk8D!-1469688737; cssln139FFR1-84816=HHg1Ld1fR7g9l751CvgpCHvkGynzgT7s!547896607; cssln133FFR1-84816=hR1nLGgLFbSZPkZ5qQPGlh9s2K6dtsGD!-733685691; cssln111HFR1-84915=ByksLGgQhJ69nNJkvTxC5PKvJMJq2jwT!565465510; cssln110HFR1-84915=nvCNLh1Q3sgcyWR2WdTG9yZJGQpkBznf!782771185; cssln112HFR1-84915=LWMDLFLCLPV6YRhtBMm46RcCKYrpvslQ!-551190033; frspplwebn2-csufresno-edu-443-PORTAL-PSJSESSIONID=Lg0Jnby8rQ4ppCfXMMsVCSYydwgnwV12!-1508339898
Accept-Language en-us,en;q=0.8,ru;q=0.5,fr;q=0.3
Host webwork2.math.csufresno.edu

or

Hi Mike,

I think moodle doesn't refresh the perl code once it has shown it (that's why in compound problems it always shows the first part), I've tested an example to see if the 'score' changes when you submit the correct answer and it's always printing score 0.

Here the example:

$a1 = 10;


BEGIN_TEXT
Write $a1
$BR $BR \{ans_rule(10) \}
$BR
END_TEXT

$ans_eval1 = num_cmp($a1);
$score = $ans_eval1->evaluate()->{score};
BEGIN_TEXT
$score
END_TEXT

ANS($ans_eval1);


I attached the screenshot once I have submitted the correct answer.

Next week I will try the solution about the page break and let you know about it.

Thanks to all,

Angel

Brian,

There seems to be an issue with reseeding the problems with dynamically generated graphs. I've just run into the issue with some of my classes.

It looks like the name of the file name of the graph image is generated by the line
my $imageName = "$studentLogin-$main::problemSeed-set${setName}prob${main::probNum}";
in the init_graph(...) from the PGgraphmacros.pl

The $main::problemSeed seems to refer to the initial problem seed, not the re-randomized problem seed. If there is a way to change that, the problem we have should go away.

It looks like there is a way to prohibit the use of cached images by setting the
$refreshCachedImages=1;
since the insertGraph(...) checks that variable. The issue with this ``solution'' is that the problem would not use the image cache at all.

It's an "external link", with the URL like this one:
http://webwork2.math.csufresno.edu/webwork2/Math75B-Nogin/

Sometimes, same students are not able to get the login page to work at some place, but then, on the same computer but in a different location, it works.

The error message they get looks like this:

Warning messages

Error messages

Expected token not present

Call stack

The information below can help locate the source of the problem.

• in Apache2::Cookie::fetch called at line 622 of /opt/webwork2/lib/WeBWorK/Authen.pm
• in WeBWorK::Authen::fetchCookie called at line 277 of /opt/webwork2/lib/WeBWorK/Authen.pm
• in WeBWorK::Authen::get_credentials called at line 219 of /opt/webwork2/lib/WeBWorK/Authen.pm
• in WeBWorK::Authen::do_verify called at line 150 of /opt/webwork2/lib/WeBWorK/Authen.pm
• in WeBWorK::Authen::verify called at line 290 of /opt/webwork2/lib/WeBWorK.pm

Request information

Method	GET
URI	/webwork2/Math76-Cusick/
HTTP Headers	User-Agent Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; WOW64; SLCC1; .NET CLR 2.0.50727; .NET CLR 3.0.04506; Media Center PC 5.0) Accept */* Connection Keep-Alive UA-CPU x86 Referer http://bb-app.csufresno.edu/webapps/blackboard/content/listContent.jsp?course_id=_24612_1&content_id=_477979_1&mode=reset Accept-Encoding gzip, deflate Cookie frspplwebn2-csufresno-edu-443-PORTAL-PSJSESSIONID=KTM2ffqky1MyVqVL0kDhrD8BGJrdymvG!-755107663; https%3a%2f%2fmy.csufresno.edu%2fpsp%2fmfs%2fcsu%2ffresno%2frefresh=list:|; ExpirePage=https://my.csufresno.edu/psp/mfs/; PS_LOGINLIST=https://my.csufresno.edu/mfs; PS_TOKENEXPIRE=24_Aug_2009_21:56:32_GMT; PS_TOKEN=AAAApAECAwQAAQAAAAACvAAAAAAAAAAsAARTaGRyAgBOcwgAOAAuADEAMBR1+/L0d7ZgKOoiOZq/I2HVo06ZxgAAAGQABVNkYXRhWHicHYs5DoAwDAQnAVFS8A+iJOLsOTqE+Arf43FsbEvjtXcNvM5XNQ6V/wo7EpGJrJlNxYadi7Pl5uDRcovbYHZkpRcXMTOYngmMegx2CZYquaT+AXKYC1M=; SignOnDefault=; csuf_auth=student; csuf_info=Hilary Heinrich~hheinrich@csufresno.edu Accept-Language en-us Host webwork2.math.csufresno.edu

Hi all,

I just finished installing WebWork on a Fedora 8 server, and everything works fine until I add the admin course. Once I click on the admin course, I get the following error:

error instantiating DB schema WeBWorK::DB::Schema::NewSQL::NonVersioned for table set_user: Can't locate object method "new" via package "WeBWorK::DB::Schema::NewSQL::NonVersioned" at /opt/webwork/webwork2/lib/WeBWorK/DB.pm line 262.
at /opt/webwork/webwork2/lib/WeBWorK.pm line 286

Also, randomly when refreshing the error page, I will get the error that it cant locate Iterator/Util.pm in @INC, however Util.pm is located at "/usr/lib/perl5/site_perl/5.8.8/Iterator/Util.pm", and "/usr/lib/perl5/site_perl/5.8.8/" is in the @INC variable path list...

Can anyone shed some light on what is wrong here, anything I can try to troubleshoot? Thanks!

Jay

Hi Joel,

Make sure that you use "shift reload" on your browser to make sure that the image is not being cached by
your browser. Having said that -- yes the image is also likely
cached on the machine as well. There is some effort made to insure that this image
is "current" but since you are doing something a bit outside the standard box
it's possible that in this case the refresh isn't behaving properly. It would take some experimenting
to figure out exactly what the problem is.

Take care,

Mike

Dear Rich,

Sometimes this problem arises because the "Refresh"
function on some operating systems and browser combinations
is a repeating key, so that a student who accidentally holds
down the F5 key (e.g., by resting a textbook on the keyboard)
can generate so many requests (6-10 per second) that the server
and Apache can't handle the load. In such cases, RAM is quickly
exhausted and swapping begins, which is untenable.

When using Apache 1, the solution involves using
Apache::SizeLimit and httpd.conf to limit
the size and number of Apache children.

Then WeBWorK can survive, but users will experience
a brief period of reduced service until the unintended
denial of service attack ends.

Your server (Pentium 3 Xeon, 512 MB RAM) may be a bit weak for a WeBWorK server.
We have 5-8 GB RAM on ours here at IU Bloomington.

Sincerely,

Bill Wheeler

I am writing a problem where the ranges on the horizontal and vertical axes depend on student inputs. I found this old thread started by nandor that suggests a fix. I ended up using a modified version of his code:
$in=time();
$gr->gifName($gr->gifName()."$in");

Anyways, in the thread John suggests that
$refreshCashedImages= 1;
will also work in webwork 2, but I couldn't get it to work in 2.4.5 using Firefox (didn't try other browsers). Not an issue since there is a workaround, just thought I would point it out.

Hi,

I'd make a couple of tests to see what is going on.

It's possible that the browser has some kind of imperfect cache of the equation pictures. Holding down the shift key while clicking refresh or reload will force the browser to fetch a new copy of the equation pictures. You could also ask the students to clear the cache of their browser and see if that helps.

The other information is to find out url of the equation picture and load it
into a separate page (right click gives you a menu that allows you to do this in some browsers -- otherwise you can inspect page source). See if that address seems recognizable. On the server side you can check to see if the file is there, delete it and then force it to be recreated.

You may have already done all of these things, but if not this will give you a bit more information to work with.

-- Mike

Workshop on Online Assessment Systems for Mathematics and Computer Science

What's Next?

Call for Submissions / Call for Participation

http://atlantis.seidenberg.pace.edu/wiki/nycoasys2008

webworknyc2008@gmail.com

There is no fee to attend this workshop.

Where: Pace University, 163 William Street, New York, NY 10038, 15th floor

When: Friday, May 2nd 2008 – 9:30 am to 5 pm

Invited speakers include:

• Dr. Michael Gage, University of Rochester, WeBWorK

• Dr. David Arnow, Brooklyn College, CodeLab

Context:

Numerous web-based assessment systems have emerged in the past few years to support the teaching and learning of mathematics (e.g., calculus, pre-calculus, algebra, and finite and discrete mathematics) and programming (e.g., for the Java, C and C++ programming languages) in introductory classes. These systems permit instructors to deliver, and (automatically) grade homework problems and distribute their solutions. Many of them are commercial initiatives (rather than free or open source) and often linked with textbooks; students pay to use them and problem sets are administered centrally. Some of them permit instructors to select and edit problems from a problem library. Rarely, they allow instructors for writing their own customized problems.

The main objectives of these systems are to: 1) engage students in active on-line learning to augment traditional practices; 2) present students with immediate and customized feedback on their progress; 3) provide students with tailored and constructive support for any problem areas they encounter; and 4) offer instructors the ability to continually monitor and assess student performance (both individually and across classes), to help guide class sessions.

These systems typically manage authenticity to prevent plagiarism and support problems ranging from true / false, multiple-choice and fill-in-the-blank type problems. To address a wider range of problems in mathematics, they need to include a particular mechanism for the treatment of symbolic mathematical formulae; for example, x+1, (x^{2-1)/(x-1) or x+sin(x)}2+cos(x)^2 should be equally accepted as an answer. In programming, such systems must be able to measure the correctness and quality (e.g., code typography) of code fragments. Correctness is generally evaluated based on running shell scripts and unit testing mechanisms. Very few systems deal extensively with code quality.

Existing Systems:

• BOSS (http://www.dcs.warwick.ac.uk/boss, Open Source, Computer Science)

• CodeLab (http://www.turingscraft.com, Commercial, Computer Science)

• CourseMarker (http://www.cs.nott.ac.uk/coursemarker, Commercial, Computer Science)

• DevSquare (http://www.devsquare.com, Commercial, Computer Science)

• Gradiance (http://www.gradiance.com, Commercial, Computer Science)

• JavaBat (http://javabat.com, Free, Computer Science)

• MathXL (http://www.mathxl.com, Commercial, Mathematics)

• MyMathTest (http://www.mymathtest.com, Commercial, Mathematics)

• OWL (http://owl.course.com, Commercial , Computer Science)

• Quiz PACK (http://www.sis.pitt.edu/~taler/QuizPACK.html, Open Source, Computer Science)

• Viope (http://www.viope.com, Commercial, Computer Science)

• WebCAT (http://web-cat.cs.vt.edu, Open Source, Computer Science)

• WeBWorK (http://webwork.rochester.edu and http://atlantis.seidenberg.pace.edu/~scharff/webwork, Open Source, Mathematics and Computer Science)

(Note: This is not an exhaustive list.)

Objectives of the Workshop:

This workshop will permit attendees to discover and/or practice with a wide range of online assessment systems for mathematics and programming. The systems will be presented by their own designers, extensive users or contributors who will focus on the philosophy behind the system, the state-of-the-art of the system and its future. This workshop is also intended to create a space of discussion for instructors in mathematics and computer science interested in building a community of instructors in mathematics and computer science interested in online assessment systems. The experience of each community can transfer to the other and create synergies.

Another objective is to discuss the future and features of the next generation of such systems. For example, some of the newest systems offer graphical-based progress and performance visualization, with error highlighting of code and hints on how to correct it. They also begin to use sophisticated data mining techniques on the repository of existing submissions to provide students' learning profiles and generate dynamic questions at the appropriate level of difficulty. After the workshop we will survey the attendees to assess their impression on the features of the next generation of online assessment systems in mathematics and programming.

Themes:

• The state-of-the-art of online assessment systems in mathematics and programming

• Teaching introductory mathematics and programming courses with online assessment systems

• Experience with teaching with different online assessment systems

• Comparison of different online assessment systems

• Designing online assessment systems for mathematics and programming

• Survey of online assessment systems in mathematics and programming

• The next generation of online assessment systems in mathematics and programming

Intended audience:

This workshop is intended for instructors involved in teaching courses in mathematics and programming, and/or interested in the design and use of online assessment systems to support students' learning and their teaching.

Schedule:

• The workshop will run from 9:30 am to 5 pm. Parallel session will be organized in the afternoon to permit mathematics and programming instructors to meet separately and discuss specifics, before convening again to share ideas.

• Refreshments and lunch will be served during the day.

Labs:

Attendees will have access to a lab to practice with existing online assessment systems in mathematics and programming.

Call for Submissions:

If you are interested in presenting at the workshop, please submit a 300-word abstract at: webworknyc2008@gmail.com with subject submission by April 15th. The abstracts will be posted on the web page of the workshop. During their presentations, speakers will be provided with a laptop, a projector and a whiteboard with pens.

Submissions will be acknowledged and authors will be notified of acceptance/rejection by April 17th.

Call for Participation:

If you do not plan to present but are interested in attending this workshop, please rsvp by sending an email to: webworknyc2008@gmail.com by April 15th with subject participation.

Contact email:

webworknyc2008@gmail.com

Support:

This workshop is funded by an NSF CCLI AI grant "Adapting and Extending WeBWorK for Use in the Computer Science Curriculum" (#0511385 and #0511391, 2005-2008)

Organizers:

Christelle Scharff, Pace University, Seidenberg School of Computer Science and Information Systems, New York, NY 10038, cscharff@pace.edu, Tel: 212 346 1016, Fax: 212 346 1863

Olly Gotel, Pace University, Seidenberg School of Computer Science and Information Systems, New York, NY 10038, ogotel@pace.edu

Andrew Wildenberg, Cornell College, Department of Computer Science, Mt Vernon, IA 52314, awildenberg@cornellcollege.edu

Richard Kline, Pace University, Seidenberg School of Computer Science and Information Systems, New York, NY 10038, rkline@pace.edu