TOPs is designed to work with compute farms that may have a variety different filesystems. For example, a TOPs user could be on a Windows machine, but also be using a Linux-based farm. The problem is how to map file paths from one filesystem to another. TOPs provides the PDG Path Map to address this.

Most TOP nodes that do work let you specify input and/or output file paths. In TOPs, each scheduler node can specify a working directory. This is because different render farm software may use different shared network filesystems. In the case you are using a farm scheduler, you should make sure that all files you output are reachable by the farm machines relative to this PDG_DIR directory.

1. Set the base working directory on the scheduler node. This directory is available to jobs as the PDG_DIR environment variable.

   • Use separate working directories for each HIP file. This is to avoid having two HIP files writing to the same PDG_DIR. Many of the default generated filenames used in parameter defaults are only unique within the HIP file.

   • For render farm schedulers, make sure that the directory is inside the network filesystem (like NFS mount or SMB share) and is shared with the render farm client machines.

2. When you use PDG_DIR or PDG_TEMP in parameter filenames, use the form __PDG_DIR__ instead of ${PDG_DIR}. If you use ${PDG_DIR}, Houdini will try and fail to expand the variable itself before the dependency graph gets it. Houdini will ignore __PDG_DIR__ syntax, but the PDG scheduler knows to expand that token to the absolute path on the executing machine.

3. Put intermediate files under __PDG_TEMP__ and final output files under __PDG_DIR__.

   • Categorize output files using subdirectories. For example, __PDG_TEMP__/geo for intermediate geometry files and __PDG_DIR__/geo for final geometry output.

• PDG_DIR

• PDG_TEMP

• PDG_SCRIPTDIR

• PDG_ITEM_NAME

• PDG_HYTHON

• PDG_RESULT_SERVER

• PDG_PATHMAP

• PDG_PATHMAP_ZONE