A unified modulo scheduling and register allocation technique for clustered processors

This work presents a modulo scheduling framework for clustered ILP processors that integrates the cluster assignment, instruction scheduling and register allocation steps in a single phase. This unified approach is more effective than traditional approaches based on sequentially performing some (or all) of the three steps, since it allows optimizing the global code generation problem instead of searching for optimal solutions to each individual step. Besides, it avoids the iterative nature of traditional approaches, which require repeated applications of the three steps until a valid solution is found. The proposed framework includes a mechanism to insert spill code on-the-fly and heuristics to evaluate the quality of partial schedules considering simultaneously inter-cluster communications, memory pressure and register pressure. Transformations that allow trading pressure on a type of resource for another resource are also included. We show that the proposed technique outperforms previously proposed techniques. For instance, the average speed-up for the SPECfp95 is 36% for a 4-cluster configuration.Peer ReviewedPostprint (published version

Hierarchical clustered register file organization for VLIW processors

Technology projections indicate that wire delays will become one of the biggest constraints in future microprocessor designs. To avoid long wire delays and therefore long cycle times, processor cores must be partitioned into components so that most of the communication is done locally. In this paper, we propose a novel register file organization for VLIW cores that combines clustering with a hierarchical register file organization. Functional units are organized in clusters, each one with a local first level register file. The local register files are connected to a global second level register file, which provides access to memory. All intercluster communications are done through the second level register file. This paper also proposes MIRS-HC, a novel modulo scheduling technique that simultaneously performs instruction scheduling, cluster selection, inserts communication operations, performs register allocation and spill insertion for the proposed organization. The results show that although more cycles are required to execute applications, the execution time is reduced due to a shorter cycle time. In addition, the combination of clustering and hierarchy provides a larger design exploration space that trades-off performance and technology requirements.Peer ReviewedPostprint (published version

Restricted Mobility Improves Delay-Throughput Trade-offs in Mobile Ad-Hoc Networks

In this paper we revisit two classes of mobility models which are widely used to repre-sent users ’ mobility in wireless networks: Random Waypoint (RWP) and Random Direction (RD). For both models we obtain systems of partial differential equations which describe the evolution of the users ’ distribution. For the RD model, we show how the equations can be solved analytically both in the stationary and transient regime adopting standard mathematical techniques. Our main contributions are i) simple expressions which relate the transient dura-tion to the model parameters; ii) the definition of a generalized random direction model whose stationary distribution of mobiles in the physical space corresponds to an assigned distribution

Synthesis and Stochastic Assessment of Cost-Optimal Schedules

We present a novel approach to synthesize good schedules for a class of scheduling problems that is slightly more general than the scheduling problem FJm,a|gpr,r_j,d_j|early/tardy. The idea is to prime the schedule synthesizer with stochastic information more meaningful than performance factors with the objective to minimize the expected cost caused by storage or delay. The priming information is obtained by stochastic simulation of the system environment. The generated schedules are assessed again by simulation. The approach is demonstrated by means of a non-trivial scheduling problem from lacquer production. The experimental results show that our approach achieves in all considered scenarios better results than the extended processing times approach

A communication-ordered task graph allocation algorithm

technical reportThe inherently asynchronous nature of the data flow computation model allows the exploitation of maximum parallelism in program execution?? While this computational model holds great promise several problems must be solved in order to achieve a high degree of program performance?? The allocation and scheduling of programs on MIMD distributed memory parallel hardware is necessary for the implementation of e cient parallel systems?? Finding optimal solutions requires that maxi mum parallelism be achieved consistent with resource limits and minimizing communication costs and has been proven to be in the class of NP complete problems?? This paper addresses the problem of static allocation of tasks to distributed memory MIMD systems where simultaneous computation and communication is a factor?? This paper discusses similarities and di erences between several recent heuristic allocation approaches and identi es common problems inherent in these approaches?? This paper presents a new algorithm scheme and heuristics that resolves the identi ed problems and shows signi cant performance bene ts?

A communication-ordered task graph allocation algorithm

technical reportThe inherently asynchronous nature of the data flow computation model allows the exploitation of maximum parallelism in program execution. While this computational model holds great promise, several problems must be solved in order to achieve a high degree of program performance. The allocation and scheduling of programs on MIMD distributed memory parallel hardware, is necessary for the implementation of efficient parallel systems. Finding optimal solutions requires that maximum parallelism be achieved consistent with resource limits and minimizing communication costs, and has been proven to be in the class of NP-complete problems. This paper addresses the problem of static allocation of tasks to distributed memory MIMD systems where simultaneous computation and communication is a factor. This paper discusses similarities and differences between several recent heuristic allocation approaches and identifies common problems inherent in these approaches. This paper presents a new algorithm scheme and heuristics that resolves the identified problems and shows significant performance benefits