HotCRP is the best available software for managing the conference review process, including paper submission, review and comment management, rebuttals, and the PC meeting. Its main strengths are flexibility and ease of use in the review process, especially through smart paper search and an extensive tagging facility. It is widely used in computer science conferences and for internal review processes at several large companies.

HotCRP also has weaknesses. It requires that you run your own server, and it does not natively support multitrack conferences (although you can hack something together).

HotCRP runs on Unix, including Mac OS X. It requires the following software:

• Apache, http://apache.org/ (You may be able to use another web server that works with PHP.)
• PHP version 5.2 or higher, http://php.net/
  • Including MySQL and GD support
• MySQL version 5 or higher, http://mysql.org/
• The zip compressor, http://www.info-zip.org/
• pdftohtml, http://poppler.freedesktop.org/ (Only required for format checking.)

Apache is preloaded on most Linux distributions. You may need to install additional packages for PHP, MySQL, and GD, such as:

• Fedora Linux: php-mysql, php-gd, zip, (poppler-utils)
• Debian Linux: php5-common, php5-gd, php5-mysql, libapache2-mod-php5 (or libapache-mod-php5 for Apache 1.x), zip, (poppler-utils)
• Ubuntu Linux: php5-common, php5-gd, php5-mysql, libapache2-mod-php5 (or libapache-mod-php5 for Apache 1.x), zip, (poppler-utils), and a package for SMTP support, such as sendmail

You may need to restart the Apache web server after installing these packages (sudo apachectl graceful or sudo apache2ctl graceful).

pdftohtml notes: HotCRP and the banal script use pdftohtml for paper format checking. As of 2013, many current Unix distributions ship with a suitable version of pdftohtml, such as “pdftohtml version 0.18.4, Copyright 2005-2011 The Poppler Developers.” Older versions of pdftohtml may not be suitable. In particular, version 0.40a can be hundreds of times slower than other versions, and version 0.39 doesn’t understand the most current PDF standard. If your pdftohtml is bad, try installing Geoff Voelker’s patched version of pdftohtml; see http://www.sysnet.ucsd.edu/sigops/banal/download.html.

Load notes: HotCRP requires a system with at least 256MB of memory, more if paper format checking is used and submission load is expected to be high. If you run HotCRP in a virtual machine, make sure you configure suitable swap space! HotCRP uses the fast, but less reliable, MyISAM database engine. If MySQL is killed your database may be corrupted.

1. Run lib/createdb.sh to create the database. Use lib/createdb.sh OPTIONS to pass options to MySQL, such as --user and --password. Many MySQL installations require privilege to create tables, so you may need sudo lib/createdb.sh OPTIONS. Run lib/createdb.sh --help for more information. You will need to decide on a name for your database (no spaces allowed).

   The username and password information for the conference database is stored in conf/options.php, which HotCRP marks as world-unreadable. You must ensure that your web server can read this file, for instance by changing its group.

2. Edit conf/options.php, which is annotated to guide you. (lib/createdb.sh creates this file based on src/distoptions.php.)

3. Redirect Apache so your server URL will point at the HotCRP directory. (If you get an Error 500, see "Configuration notes".) This will generally require adding a <Directory> for the HotCRP directory, and an Alias redirecting a particular URL to that directory. This section of httpd.conf makes "/testconf" point at a HotCRP installation in /home/kohler/hotcrp; it works in Apache 2.2 or earlier.

    <Directory "/home/kohler/hotcrp">
        Options Indexes Includes FollowSymLinks
        AllowOverride all
        Order allow,deny
        Allow from all
    </Directory>
    Alias /testconf /home/kohler/hotcrp
   

   Apache 2.4 or later requires this instead.

    <Directory "/home/kohler/hotcrp">
        Options Indexes Includes FollowSymLinks
        AllowOverride all
        Require all granted
    </Directory>
    Alias /testconf /home/kohler/hotcrp
   

   Note that the first argument to Alias should NOT end in a slash. The "AllowOverride all" directive is required.

   All files under HOTCRPROOT (here, "/testconf") should be served by HotCRP. This normally happens automatically. However, if HOTCRPROOT is /, you may need to turn off your server’s default handlers for subdirectories such as /doc.

4. Update the systemwide setting for PHP’s session.gc_maxlifetime configuration variable. This provides an upper bound on HotCRP session lifetimes (the amount of idle time before a user is logged out automatically). On Unix machines, systemwide PHP settings are often stored in /etc/php.ini. The suggested value for this setting is 86400, e.g., 24 hours:

    session.gc_maxlifetime = 86400
   

   If you want sessions to expire sooner, we recommend you set session.gc_maxlifetime to 86400 anyway, then edit conf/options.php to set $Opt["sessionLifetime"] to the correct session timeout.

5. Edit MySQL’s my.cnf (typical location: /etc/mysql/my.cnf) to ensure that MySQL can handle paper-sized objects. It should contain something like this:

    [mysqld]
    max_allowed_packet=32M
   

   max_allowed_packet must be at least as large as the largest paper you are willing to accept. It defaults to 1M on some systems, which is not nearly large enough. HotCRP will warn you if it is too small. Some MySQL setups, such as on Mac OS X, may not have a my.cnf by default; just create one. If you edit my.cnf, also restart the mysqld server. On Linux try something like sudo /etc/init.d/mysql restart.

6. Sign in to the site to create an account. The first account created automatically receives system administrator privilege.

   If your server configuration doesn’t let .htaccess files set options, Apache will report an “Error 500” when you try to load HotCRP. Change your Apache configuration to AllowOverride All in the HotCRP directory, as our example does above.

You can set up everything else through the web site itself.

• Configuration notes

  • Uploaded papers and reviews are limited in size by several PHP configuration variables, set by default to 15 megabytes in the HotCRP directory’s .htaccess.

  • HotCRP PHP scripts can take a lot of memory, particularly if they're doing things like generating MIME-encoded mail messages. By default HotCRP sets the PHP memory limit to 128MB.

  • HotCRP benefits from Apache’s mod_expires and mod_rewrite modules; consider enabling them.

  • Most HotCRP settings are assigned in the conference database’s Settings table. The Settings table can also override values in conf/options.php: a Settings record with name "opt.XXX" takes precedence over option $Opt["XXX"].

Run lib/backupdb.sh at the shell prompt to back up the database. This will write the database’s current structure and comments to the standard output. HotCRP stores all paper submissions in the database, so the backup file may be quite large.

Run lib/restoredb.sh BACKUPFILE at the shell prompt to restore the database from a backup stored in BACKUPFILE.

Run lib/runsql.sh at the shell prompt to get a MySQL command prompt for the conference database.

HotCRP code can be updated at any time without bringing down the site. If you obtained the code from git, use git pull. if you obtained the code from a tarball, copy the new version over your old code, preserving conf/options.php. For instance, using GNU tar:

% cd HOTCRPINSTALLATION
% tar --strip=1 -xf ~/hotcrp-NEWVERSION.tar.gz

HotCRP can run multiple conferences from a single installation. The last directory component of the URL will define the conference name. For instance:

http://read.seas.harvard.edu/conferences/testconf/doc/testconf-paper1.pdf
                                         ^^^^^^^^
                                      conference name

The conference name can only contain characters in [-_.A-Za-z0-9], and it must not start with a period. HotCRP will check for funny conference names and replace them with __invalid__.

To turn on multiconference support, edit conf/options.php and set $Opt["multiconference"] to true. You will then need to tell HotCRP how to find the options relevant for each conference. The most flexible mechanism is to use $Opt["include"] to include a conference-specific options file. For example (note the single quotes):

$Opt["include"] = 'conf/options-${confname}.php';

The ${confname} substring is replaced with the conference name. HotCRP will refuse to proceed if the conference-specific options file doesn’t exist. To ignore nonexistent options files, use wildcards:

$Opt["include"] = 'conf/[o]ptions-${confname}.php';

${confname} replacement is also performed on these settings: dbName, dbUser, dbPassword, sessionName, downloadPrefix, conferenceSite, and paperSite.

You will still need to create a database for each conference using the lib/createdb.sh script (the -c CONFIGFILE option will be useful). Also, you will need to convince your Apache to use the HotCRP install directory for all relevant URLs.

If you don't want to use the last directory component, set $Opt["multiconferenceUrl"] to a URL regular expression, a space, and a replacement pattern. HotCRP matches the input URL to the regex. If it matches, it constructs a conference name from the replacement pattern. For example, this setting will use "conf_CONFNAME" as the conference name for a URL like "http://CONFNAME.crap.com/":

$Opt["multiconferenceUrl"] = '\w+://([^./]+)[.]crap[.]com[.]?/ conf_$1';

HotCRP is available under the Click license, a BSD-like license. See the LICENSE file for full license terms.

Eddie Kohler, Harvard/UCLA

• HotCRP is based on CRP, which was written by Dirk Grunwald, University of Colorado
• banal by Geoff Voelker, UCSD