Resolution:
The ScoringDiscriminator can be used to implement a two-tiered "fat task / thin task" hierarchy in the GridServer 4.1 scheduler. ScoringDiscriminator applies within a Service, and you will want to apply a ScoringDiscriminator to all tasks.

Consider a scenario where you prefer to run fat tasks on engines with CPU speed >= 2.4 MHz, and thin tasks on engines with CPU speed < 2.4 MHz. If no preferred Engines are available, tasks will take any available Engine.

Create two ScoringDiscriminators as follows:

Fat task ScoringDiscriminator {
    cpuMHz >= 2400
    cpuMHz >= 0
  }

Thin task ScoringDiscriminator { cpuMHz < 2400 cpuMHz < 100000 }

Attach the discriminators to invocations as specified. As the scheduler matches Engines to tasks for a particular service, it will match those Engine-task pairs with a score of two (fat tasks on cpuMHz >= 2400 and thin tasks on cpuMHz < 2400) before it matches those Engines with the default score of one.

Note that scoring discriminator depth is configurable in the Manager admin, to prevent N-squared searches.