Each machine that you use to execute modules remotely must have most of Explorer installed on it. In general, the version installed remotely must match the version installed on the local machine.

This sense of remote execution is different from that offered by the X Window System, which lets you remotely log into a workstation on which Explorer is installed, reset the DISPLAY environment variable to reference your own screen, and then run Explorer. In this case, all of Explorer will initially be running on the remote machine, but the user interface will appear on the local machine.

To execute Explorer modules remotely, you must first add any host names used to your .explorerrc file, in this format:

host hostname

For example, suppose your local machine, called billiejoe, is networked to another machine named bob. If you can remotely login into bob, Explorer is installed on it, and then you can very simply set up the two machines for remote execution.

Add this line to the .explorerrc file:

host bob

Do this for every host you want to run modules on. When you execute Explorer again, these host names will be listed on the Hosts menu in the Module Librarian window.

Explorer uses the rsh command to create a computation server on machines used for execution of remote modules. Hence, you must be able to access the remote hosts you use with the rsh command. Explorer also provides an alternative to rsh, which is cxrexec. It is capable of prompting for a password.

See “Remote Execution and Passwords” for more information.

If you have a single .cshrc file on several workstations, each of which may have Explorer installed in a different location, you can use the csh “switch” statement to set EXPLORERHOME correctly according to the current machine.

For example:

switch (`hostname`)
case billiejoe:
       setenv EXPLORERHOME /usr/local/explorer
       breaksw
case bob:
       setenv EXPLORERHOME /usr/people/jim/explorer
       breaksw
endsw

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Note: The character (`) surrounding hostname in the previous example is an accent grave, not an apostrophe.

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The module path is a list of directories in which Explorer looks for modules and maps. The default list contains only $EXPLORERHOME/modules, but the Explorer.config file shipped with Explorer extends it. You can reset module paths from scratch, or you can extend them using the “-append” modifier.

Configuration Commands

The commands that are accepted in an Explorer configuration file are described below. Optional portions are enclosed in square brackets. Ellipses denote that the previous argument may be repeated any number of times. Commands (reserved words) are shown in bold.

The modulepath command states where to look for modules.

modulepath [-prepend] 


path ...

This command defines a list of directories to be used. By default, the existing module path is extended by the list for directories. The default path value is $EXPLORERHOME/modules. Used alone, the command clears the module path. If the “-prepend” option is used, the path is added at the head of the current directory list.

You can use the set command to set the size of the temporary directory and the arena.

set tempdir

Explorer uses a number of temporary files during its execution. While almost all of these are small, the shared memory arena file can get quite large.

set tempdir 


path

The set tempdir command states where to place any temporary files that may be needed during the course of execution, such as named pipes and shared memory arena files, if applicable. Typically, such files are placed in a uniquely named subdirectory of the directory. The default value for the base directory is /usr/tmp.

Because shared memory arenas can become large, it is often advantageous to place the tempdir somewhere other than below /usr.

set arenasize

On some workstations, modules use shared memory for data communications. The shared memory is mapped into a file that resides on disk as determined by the set tempdir command above.

set arenasize 


string

For a shared memory system, make the maximum size of the shared memory arena the designated size.

The “string” should be a number optionally followed by “mb” or “kb” for megabytes and kilobytes, respectively. This option may also be set from the command line. The default size is 16Mb.

Defines a new Module Librarian category with the name “name” and containing the list of modules given.

category name [-append] [-filter] [arg] module ...

The -append option appends a list of modules to a specified category. The list of modules can contain module names, such as GenLat, or directory names. In the latter case, the directory is added to the module path, and all modules and maps in the directory are added to the category. For example,

category myModules ~/explorer/modules

If the module name is MODULES, then all modules are added to the category. You can use the -filter option with an arg to filter the list of modules against the argument pattern. The arg accepts shell wildcards such as *, ? and [. For example,

category Readers -filter Read* Modules

puts all the Read* modules in a category called Readers.

There is a designated category in the Module Librarian called “shelf.” Modules in the shelf category are displayed in a small panel at the bottom of the Librarian's window.

Modules are organized by categories and by hosts in the Module Librarian. When you add a host, modules can be executed on that machine.

host [-command string] name

The modifier “-command” may be used to define an alternative way of starting a local communications server (LC) on remote hosts. The single argument after “-command” (which must be enclosed in quotation marks if it contains blanks) specifies an alternative command.

The UNIX command Explorer uses to start the LC on a remote host is the given command (rsh by default) followed by the hostname, followed by a shell command. This shell command will be invoked remotely to start the LC. For example, suppose this appears in your .explorerrc file:

host bob -command “myrsh -x”

Explorer will invoke

myrsh -x bob <special command>

to start the LC.

If the word HOST appears in the alternative command, the hostname is placed there instead of at the end. Therefore, you can use the command:

host bob -command “rsh HOST -l joe” 

to start a remote LC under the account “joe” on bob.

You may see see one of the following changes:

For visual image-processing, the tradeoff of speed against accuracy is often acceptable. In cases where full accuracy is important, you can override the default behavior by setting the environment variable IL_HW_ACCELERATE before starting Explorer. This will give you full floating point accuracy in the modules listed above:

setenv IL_HW_ACCELERATE 0
explorer

To restore the default behavior of the modules, you can use either of these commands:

setenv IL_HW_ACCELERATE 1
explorer

or

unsetenv IL_HW_ACCELERATE
explorer