Clipper

If Group By attributes are selected, features with the same values in the Group By attributes are placed into the same set, and clipping occurs in each set independent of other sets.

How parallel processing works with FME: see About Parallel Processing for detailed information.

This parameter determines whether or not the transformer should perform the work across parallel processes. If it is enabled, a process will be launched for each group specified by the Group By parameter.

Parallel Processing Levels

Parameter	Number of Processes
No Parallelism	1
Minimal	coresThe processor, or CPU, is the physical part of the computer that performs mathematical calculations. It is the most important part of a computer system. Traditional processors have only one core on the processor, meaning that at any given time, only one set of calculations is being performed. If a processor is dual-core, this means the single chip contains hardware for two processors, now called cores to distinguish them from the single chip, running simultaneously, side by side. (Source: http://www.ehow.com/facts_5730257_computer-core-processors_.html) / 2
Moderate	exact number of cores
Aggressive	cores x 1.5
Extreme	cores x 2

For example, on a quad-core machine, minimal parallelism will result in two simultaneous FME processes. Extreme parallelism on an 8-core machine would result in 16 simultaneous processes.

You can experiment with this feature and view the information in the Windows Task Manager and the Workbench Log window.

• Single Clipper: Only a single CLIPPER feature will be used.
• Multiple Clippers: All CLIPPER features will be used.  
• Clippers First: The Clipper assumes that all CLIPPER features will enter the transformer before any CLIPPEE features. Any further CLIPPER features that arrive after the first CLIPPEE will be logged with a warning and discarded.

If the Merge Attributes parameter is enabled, any CLIPPEE that is clipped will receive the attributes from the CLIPPER feature.  In such a case, the Merge Attribute Prefix parameter can be used to give the CLIPPER's attributes a prefix before they are added to the CLIPPEE.

This attribute (if specified) will be added with a value of “yes” to any features output via either the INSIDE or OUTSIDE port which were cut by the transformer, and a value of “no” to any output features which were not changed by the transformer.

This parameter directs what action should be taken with CLIPPEE features that lie entirely on the boundary of the clipper.

• Treat as Inside: These features that lie on the boundary are output via the INSIDE port.
• Treat as Outside: These features that lie on the boundary are output via the OUTSIDE port.
• Treat as Inside and Outside: Points and line segments on the boundary are duplicated and output as both INSIDE and OUTSIDE.

If the Create Aggregates parameter is No, then features that are clipped into multiple parts will not be aggregated, but rather each part will be output as a separate feature.

If this parameter is set to No, the INSIDE rasters which were clipped will be equal to the intersections of the clippers and clippees. Otherwise, the intersections will be padded by nodata so that the extents are identical to those of the input rasters.