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 your local machine. This node also runs its scheduled work items in parallel.

This node lets you:

These parameters are not related to the multi-threading of individual processes. To control the multi-threading of Houdini work items, use the Houdini Max Threads parameter.


To execute work items on a farm or on remote machines, use a different scheduler like the HQueue Scheduler.



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.

Temp Directory


Determines where the local temporary files are written to.

Files that are written to this location are needed for the PDG cook, but are not typically the end product and can be removed when the cook completes. For example, log files and python scripts are some of the files that are usually written during the cook.

Working Directory

Use pdgtemp subdirectory specified in the Working Directory field.

Houdini Temp

Use pdgtemp subdirectory of $HOUDINI_TEMP_DIR.


Use the custom directory specified by in the Custom field.

Append PID

When on, a subdirectory is added to the location specified by the Location parameter and is named after the value of your Houdini session’s PID (Process Identifier). The PID is typically a 3-5 digit number.

This is necessary when multiple sessions of Houdini are cooking TOP graphs at the same time.


This parameter is only available when Directory Location is set to Custom.

The full path to the custom temporary directory.

Total Slots

Specifies the number of available slots for this scheduler to use when executing work items. This also provides some default slot counts based on the detected CPU. A higher slot count means more work items can run at once.

For more information, see limiting resource usage.

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 specified in the Custom Slot Count field.

Custom Slot Count

The number of slots available to execute work items. A positive number sets the slot count. A negative number sets the slot count as the total logical CPU cores minus the number specified in this field.

Verbose Logging

Print extra debugging information in job output logs.

Job Parms

Job-specific parameters.


You can override these parameters per node with the Edit Parameter Interface. For more information, see Scheduler Job Parms / Properties.



When on, only one single work item is executed at a time.

Slots Per Work Item

When on, sets the number of slots consumed by each work item. Work items are only run by the scheduler if at least this number of slots are available.


The total number of slots that are available to the scheduler is determined by the Total Slots parameter setting.

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


When a work item process terminates with a non-zero exit code, it is marked as failed by default. These parameters change that behavior.

On Task Failure

Report Error

The work item will fail.

Report Warning

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

Retry Task

The work item will be restarted immediately, according to the parameters below.


The work item will succeed.

Handle All Non Zero

When on, lets you specify a particular exit code with the Exit Code field, all other non-zero will be regarded as a failure.

Exit Code

This parameter is only available when Handle All Non Zero is off.

Specifies the exit code that is handled by the On Task Failure parameter setting. All other non-zero exit codes are treated as a failure as normal.

Maximum Retries

Sets the maximum number of times the task will be restarted.

Retry Count Attribute

When enabled, add an int attribute set to the number of times the task was restarted.

Task Environment

Houdini Max Threads

When on, sets the maximum number of threads each work item can use. This also sets the HOUDINI_MAXTHREADS environment value which is used by Houdini-based programs like Mantra, Karma, Hython, and HBatch.

Requires GUI Window


When on, your work items can run GUI Applications in pop-up windows.

Normally, processes are started such that they do not pop up command windows on the desktop when they run. However, some Windows applications require a GUI window.

Environment Variables

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.

See also

TOP nodes