PSDFScheduler
ptolemy.domains.psdf.kernel.PSDFScheduler

A scheduler that implements basic scheduling of PSDF graphs. PSDF scheduling is similar to SDF scheduling, EXCEPT: <p> 1) Because parameter values may change, the solution to the balance equation is computed symbolically. i.e. the repetitions vector is a function of the parameter values. <p> 2) Because the firing vector may change, the schedule determined by this class can only be a quasi-static, or parameterized schedule. Note that parameterized schedules cannot generally be constructed for models with feedback or with unconstrained parameter values. <p> This class uses a ConstVariableModelAnalysis to determine which scheduling parameters are constants and which may change during execution of the model. Rate parameters that can change are checked to ensure that their change context is not strictly contained by the model being scheduled. If this is the case, then the actor is not locally synchronous, and cannot be statically scheduled. Dynamic parameters with a valid changed context are treated symbolically when computing the repetitions vector. <p> After computing a schedule, this scheduler determines the external rate of each of the model's external ports. Since the firing vector is only computed symbolically, these rates can also only be computed symbolically. The dependence of these external rates on the rates of ports in the model is declared using a DependenceDeclaration. Higher level directors may use this dependence information to determine the change context of those rate variables and may refuse to schedule the composite actor if those rates imply that this model is not locally synchronous. <p> This scheduler uses a version of the P-APGAN scheduling algorithm described in [1]. <p> [1] B. Bhattacharya and S. S. Bhattacharyya. Quasi-static scheduling of reconfigurable dataflow graphs for DSP systems. In <em> Proceedings of the International Workshop on Rapid System Prototyping </em>, pages 84-89, Paris, France, June 2000.

Author(s): Stephen Neuendorffer, Shuvra S. Bhattacharyya
Version:$Id: PSDFScheduler.doc.html,v 1.1 2006/02/22 18:41:22 mangal Exp $
Pt.Proposed Rating:Red (neuendor)
Pt.Accepted Rating:Red (neuendor)