Limit on number of exams and pages

Added by S. McKay over 7 years ago

Hi,
I have looked through the manual, but couldn't find the answer I need. If it is there, I apologize.
I would like to know the upper limit for number of exams and pages. Since every page of every exam has a unique barcode, this translates to the practical limit of the barcode. For example, if I have 1000 calculus students take an exam, that is 10 pages long, I would need 10*1000 separate barcodes. My questions are:

a) Can this even be done in AMC?
b) If so, is it practical?
c) Has anyone used AMC for this many tests?

There are logistical problems associated with this many exams, such as scanning, etc. However, I am worried about the practical limitations of the software.

I would like to run a "test", one midterm via AMC, but am a little worried.

Thanks,
S.M.


Replies (11)

RE: Limit on number of exams and pages - Added by Alexis Bienvenüe over 7 years ago

See note 4 of #302 for a description of the barcode.
The default values (you can change it at the beginning of your document)

\AMC@NCBetud=12
\AMC@NCBpage=6

mean that you should be able to make up to 2^12-1=4095 different papers, with up to 2^6-1=63 pages each.

I've not used AMC with more than 100 students, but see RE: Performance d'AMC sur 634 copies for a (french) report of using AMC with 634 students (one separate answer sheet), and a user also reported a 4080 students run in Trop grand nombre de fichiers générés (also in french, some problems that should not appear anymore with recent versions of AMC). Be ready to fill your hard drive with a lot of rubish: AMC is not very thrifty.

Please tell us your feelings after the test!

RE: Limit on number of exams and pages - Added by S. McKay over 7 years ago

Thanks! my numbers should be less than that. I am still trying to convince them to try AMC. I'll let you know if and when it happens.

RE: Limit on number of exams and pages - Added by shreikant kv over 7 years ago

We ran AMC recently with about 3000 students. The question paper had
80 questions on around 10 pages with some extra pages for rough work.
I suppressed printing of bar codes on question paper part. There were
separate bubble sheets.

Please avoid oval bubbles with this number of students. On a "modern"
desktop you would need a couple of hours for to generate DOC-sujet and
similar time for evaluation. Scan the bubble sheets to jpg directly (page
by page option -- hopefully available on your scanner) rather than pdf.
The native print to pdf took over 12 hours to split DOC-sujet to individual
files for each student. In hindsight I would recommend that you run a
script using pdftk on DOC-sujet.

Please do not run AMC without fully testing it on such large classes. However,
I persistently faced and still face the following problem: I had macros in
.tex file with 1 or 2 students in test phase and full 3000 students in actual
phase. However, when I ran the full AMC cycle (including evaluation) on test
phase and switched to actual phase -- the "update marking scheme" never
worked. If you are running test phase I would advise you to run it as a
separate AMC project.

I can post scripts and template if you are interested.

If you are modifying \AMC@NCBetud -- you have to wrap it within \makeatletter
and \makeatother.

RE: Limit on number of exams and pages - Added by Alexis Bienvenüe over 7 years ago

Thank you very much for this very interesting report. Can you tell us which version of AMC you used for this run?

However, when I ran the full AMC cycle (including evaluation) on test
phase and switched to actual phase -- the "update marking scheme" never
worked.

Can you help us reproduce this bug with some source files and instructions? I made a short test with a simple source file, running a full cycle with 5 students and then another full cycle with more students, but I could not reproduce the problem.

RE: Limit on number of exams and pages - Added by shreikant kv over 7 years ago

I used AMC version 1.2.1.

I tried to reproduce the bug but (un)fortunately could not!

RE: Limit on number of exams and pages - Added by Alexis Bienvenüe over 7 years ago

The native print to pdf took over 12 hours to split DOC-sujet to individual
files for each student. In hindsight I would recommend that you run a
script using pdftk on DOC-sujet.

AMC 1.2.1 uses gs to split DOC-sujet to individual files, which shows to be faster than pdftk in some situations.
Can you try the following commands on your large (more than 500 pages) DOC-sujet.pdf?

time pdftk DOC-sujet.pdf cat 500-510 output a.pdf
time gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=b.pdf -dFirstPage=500 -dLastPage=510 DOC-sujet.pdf

and compare the times (and the produced files a.pdf and b.pdf) for different slice positions?
What script are you using to split DOC-sujet?

RE: Limit on number of exams and pages - Added by shreikant kv over 7 years ago

Output of "timing" pdftk and gs for splitting a pdf file:

Looks like pdftk uses more "system time" but less "user time" and "real time".

$ time gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=b.pdf -dFisrtPage=500 -dLastPage=1000 DOC-sujet.pdf

real 2m6.300s
user 2m4.168s
sys 0m1.300s

$ time pdftk DOC-sujet.pdf cat 500 1000 output a.pdf

real 0m16.481s
user 0m13.213s
sys 0m3.084s

RE: Limit on number of exams and pages - Added by shreikant kv over 7 years ago

In the eariler reply, I had cat "500 1000" instead of "500-1000".

Even then, pdftk beats gs in "real time".

$ time pdftk DOC-sujet.pdf cat 500-1000 output a.pdf

real 0m16.609s
user 0m13.201s
sys 0m3.208s

RE: Limit on number of exams and pages - Added by shreikant kv over 7 years ago

I use the attached script to split DOC-sujet.pdf.

It figures out number of students, number of pages per student -- of question paper
and bubble sheets and then uses pdftk to split.

filesplitter (1.3 kB)

RE: Limit on number of exams and pages - Added by Alexis Bienvenüe over 7 years ago

OK, thanks. When copies do not have the same number of pages, this can fail.
I will add a configuration option to AMC to use pdftk or gs (with default value pdftk) to extract pages from the PDF.

RE: Limit on number of exams and pages - Added by Alexis Bienvenüe over 7 years ago

I will add a configuration option to AMC to use pdftk or gs (with default value pdftk) to extract pages from the PDF.

Done with hg:685fc3228f2e.

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