Houdini 18.0 Nodes TOP nodes

Local Scheduler TOP node

Schedules work items on the local machine.

This node is the default scheduler that executes work items on the local machine. Works items are scheduled to run in parallel. The total number of work items running at once is specified by the parm Total Slots in combination with the job parm Slots Per Work Item. Total Slots is how you set the total resources of the scheduler, and Slots Per Work Item is how to tweak how many work items should run at once. Note that these settings are not related to multithreading of individual processes. For Houdini work items, that can be controlled by Houdini Max Threads.


If some tasks consume a lot of computational or memory resources, you can use the job parm Slots Per Work Item to change the maximum number of such processes that are run in parallel. For example by default if there are 8 Slots available as determined by Total Slots there will be a maximum of 8 processes executed in parallel. However if Slots Per Work Item is set to 2 on the processor node, there will be a maximum of 4 such processes executed in parallel, with each task consuming 2 Slots worth of resources in the scheduler.

To execute work items on a farm or remote machines, another scheduler should be utilized such as HQueue Scheduler.



These are global parameters for all work items using this scheduler.

Working Directory

The relative directory where the work will be generating intermediate files and output. The intermediate files will be placed in a subdirectory. For the Local scheduler or Hqueue, typically $HIP is used. For other schedulers, this should be a relative directory to Local Shared Root Path and Remote Shared Root Path; this path is then appended to these root paths.

Directory Location

Select where local temporary files should be written. Files that are written here are needed for the PDG cook, but are typically not the end product, and can be removed when the cook completes. Log files and python scripts are examples of files that are typically written during the cook.

Working Directory: A pdgtemp sub directory of the Working Directory

Houdini Temp: A pdgtemp sub directory of $HOUDINI_TEMP_DIR

Custom: A custom directory specified by Custom Directory

Append PID

Adds a sub directory to the Location specified by Directory Location, which is the value of the PID (Process Identifier) of your session of Houdini. This is typically a 3-5 digit number. This is necessary if multiple sessions of Houdini are cooking TOP graphs at the same time.

Custom Directory

The full path to the temporary directory when Directory Location is set to Custom.

Total Slots

Specify the number of Slots that are available for this scheduler to use to execute work items. Provides some default Slot counts based on the detected CPU. A higher slot count means more work items can run at once.

Equal to 1/4 of Total CPU Count: Use the number of logical cores divided by four.

Equal to CPU Count Less One: Use the number of logical cores less 1.

Custom Slot Count: Use the number as specified by Custom Slot Count.

See limiting resource usage.

Custom Slot Count

The number of Slots available to execute work items. Positive numbers indicates the Slot count. A negative number indicates that the Slots count will be the total logical CPU cores minus the specified number.

Job Parms

These job specific parameters can be overridden by each node under the Local Scheduler tab on the node’s Schedulers parameter interface. See Scheduler Job Parms / Properties.



Enabling this will force only one single work item to be executed at a time.

Slots Per Work Item

The number of Slots consumed by each work item. This work item will only be run by the scheduler if at least this number of Slots are available. The total number of Slots available to the scheduler is specified by Total Slots.

Non-Zero Exit Code Handling

When a work item processes terminates with a non-zero exit code, it will be marked as failed by default. Use these parameters to change that behavior.

Handle By

Reporting Error: The work item will fail.

Reporting Warning: The work item will succeed and a warning will be added to the node.

Retrying Task: The work item will be restarted immediately.

Ignoring Exit Code: The work item will succeed.

Handle All Non Zero

Set this to false to specify a particular exit code.

Exit Code

Set this to the exit code that you wish to handle using Handle By. All other non-zero exit codes will be treated as a failure as normal.

Task Environment

Additional work item environment variables can be specified here.


Name of the work item environment variable.


Value of the work item environment variable.

Houdini Max Threads

Specify the maximum number of threads to use for each work item. This sets the HOUDINI_MAXTHREADS environment value which is used by Houdini-based programs such as Mantra, Karma, Hython and HBatch.

See also

TOP nodes