Threading in TerraScan, TerraMatch and TerraPhoto

Most customers run a processor with four cores, high quality models today have eight cores . Each core supports a maximum of two threads. TerraScan (TerraSlave ) currently supports a maximum of 128 threads. To benefit from all threads you should have a PC with eight processors with eight cores. If you are a standard user, please select a PC with eight processors and use twelve threads. If you use all sixteen cores, TerraScan/TerraSlave may take all resources of your PC in processing.

Here is a description of the typical way in which threading in TerraScan, TerraMatch and TerraPhoto works:

  • The software has 24 million points to process.
  • User has allowed maximum 6 threads.
  • Software will assign 4 million points for each thread to process and launches 6 threads.
  • Because of variations in local point density (or some other factor) some of the points require less computation, some require more.
  • Therefore the 6 processing threads will not take the same amount of time to run.
  • The processor usage may be 100% in the beginning and stay there for a while.
  • As threads complete, you will see the processor usage dropping.

On good computer hardware you can start more threads than the number of processor cores you have. For example, if you have 6 cores, you may set maximum number of threads to 8 or 10. This will ensure that the processor usage stays close to 100% for a longer time.

If you have hyper threading enabled, Windows will display a misleading processor usage number. When software is utilizing all real processor cores, Windows will display processor usage as 50%. Hyperthreading adds almost no processing power.

To configure TerraScan to use the desired thread count you need to set the Processor Usage in the TerraScan settings. A similar setting needs to be set in TerraSlave (TSlave->File->Settings).


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