** Using WeBWorK **

At Hartford, we started the year with a new server, new version of WebWork and optimism.  The server is fast and we have more instructors using the system, more students and faster response.  But purple screens keep popping up.  They all seem to lead to PG_Sort.  We moved from WW1.7 to 1.9.  We moved form Unix to RedHat Linux Ver. 9.  We moved from Perl 5.6 to Perl 5.8.  I am betting on the last change as being the culprit.  I read in http://www.perldoc.com/perl5.8.0/lib/sort.html that sort changed from 5.6 to 5.8.  I don't know enough to go any farther. 

John Williams

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Unfortunately I don't have perl 5.8 running on any of our webwork systems here. Can you give a sample of the errors (including errors from the log file) that occur? If they are long you can send them to me via email rather than post them. I'll do what I can.

-- Mike (gage@math.rochester.edu)

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On one hand, you say that you are getting lots of pink screens, but not very many WW problems call sort directly. So, I assume you have examples of troublesome problems which don't mention sort.

The next thing I would check is if there are problems which don't use list or interval evaluators (each of which sorts things internally). Depending on the problems you use, these may occur pretty infrequently.

If all pink screen problems fall into the categories above, then sort probably is the problem. But, if you have a problem which causes pink screens and does not directly call sort, PG_sort, number_list_cmp, or interval_cmp, then sort seems unlikely to be the culprit. In that case, you might point to a simple problem or two which still causes pink screens.

John

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I have the error reproduced on our linux system. In the function PGsort in the file PGtranslator.pm the values $a and $b used in the sort are not being passed into the comparison function. I can't figure out why right at the moment. If someone else can duplicate they error, perhaps they can see what I'm missing.

--Mike

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Here is a set definition file for problems in the demo course that all cause pink screens.  They do seem to all rely on sort in some manner.

setNumber=SortProblems

openDate = 05/01/02, 0600

dueDate = 1/1/10 at 2:00am

answerDate = 1/1/10 at 2:00am

paperHeaderFile = paperSetHeader.pg

screenHeaderFile = screenSetHeader.pg

problemList =

setSampleAnswers/sample_str_ans.pg, 1

setGenericQuestions/CheckboxMult.pg, 1

setIntegrals25RationalFunctions/nsAP_F_22.pg, 1

setAlgebra23PolynomialZeros/srw3_3_21.pg, 1

John Williams

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-Tom

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You can run the script:

#!/path/to/webwork/perl
printf( "%-20s %10s\n","Module","Installed");
foreach $module ( GD,HTML::Parser,HTML::Tagset,MIME::Base64,Dig est::MD5,URI ){
   eval "require $module";
   printf( "%-20s%10s\n", $module, $module->VERSION) unles s ($EVAL_ERROR);
}

my output is

Module    Installed
GD    1.40
HTML::Parser    3.26
HTML::Tagset    3.03
MIME::Base64    2.12
Digest::MD5    2.20
URI    1.19

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On our site (where we can reproduce the error) this gives:

[apizer@hilbert test]$ perl test.pl
Module                Installed
GD                        2.07
HTML::Parser              3.28
HTML::Tagset              3.03
MIME::Base64              2.20
Digest::MD5               2.20
URI                       1.21

but I don't understand what any of these would have to do with PGsort.

Arnie

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#!/usr/bin/perl -w

use strict;

sub PGsort {

my $compare = shift;

sort {&$compare($a, $b) } @_;
}

my @list = (4, 5 ,10, 8, 9 );

my $str = join( " ", PGsort sub {$_[0] <=> $_[1] } , @list );

print $str;

Now to find out why it doesn't work in context.

--Mike

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http://archive.develooper.com/perl5-porters@perl.org/msg87643.html

has a discussion of how $_[1] is not handled quite right, I don't know if it applies here or not.

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