Force-directed scheduling

Other control step schedulers, force-directed scheduling, force-directed list scheduling, a second-order differential equation example, a pipelined 16-point digital FIR filter example, and a fifth-order digital elliptic wave filter example. 

As elaborated above the establishment of the first allocation plan is complex both in terms of technical and process issues. An additional factor that characterised the first allocation process was the very tight time schedule. The Directive was politically agreed in July 2003 and formally entered into force on 25 October 2003. This means that the first allocation plans were due less than six months after the formal entry into force of the Directive. 

Paulin, P. G and Knight, J. P. (1989) Force-Directed Scheduling for the Behavioral Synthesis of ASICs. IEEE Transactions on Computer-Aided Design, Vol 8, No 6, pp 661-679. 

P. Paulin and J. Knight. Force-directed scheduling for the behavioural synthesis of ASICs. IEEE Transactions on CAD of Integrated Circuits and Systems, CAD-8, number 6, pages 661-679, Jun 1989. 

A more complex scheduling method is force-directed scheduling [55], used in HAL [54] and SAM [23]. Force-directed scheduling aims at balancing the number of operations in each control step. To do this, the mobility is first quantified into time frames (Figure 7(a)). The width of a time frame is the probability of an operation being scheduled in that particular control step, initially 1/n, where n is the number of possible control steps in which that operation can be scheduled. For example, operation 1 must be scheduled in control step 1 and thus has a time frame... 

P.G. Paulin and J.P. Knight, Force-Directed Scheduling in Automatic Data Path Synthesis, Proceedings 24th Design Automation Conference, pp. 195-202, Miami Beach, Florida, June 1987. 

Done by the InHAL module, using a force-directed scheduling algorifiim that tries to schedule the operations so as to balance the distribution of operations using the same hardware resources, without lengthening the schedide. First, both an ASAP schedule... 

Done by the InHAL module, first scheduling the operations on the critical path, then the others. For the others, both an ASAP schedule and an ALAP schedule are generated, and the results combined to indicate the possible control steps for each operation. Operations are distributed when possible to minimize the scheduling of similar operations into the same time step. The MidHAL module is Ihen called to estimate the allocation of operations to functional units, and operations are reassigned when necessary to minimize the scheduling of operations using similar resources into the same time step. Note that there is no mention here of force-directed scheduling. 

Pierre G. Paulin and John P. Knight, Force-Directed Scheduling for the Behavioral Synthesis of ASIC s , IEEE Trans, on CAD, pages 661-679, June 1989. 

SAM C cheduling, Allocation, and Mapping uses concepts taken from force-directed scheduling to perform scheduling and data path synthesis. First, ASAP and ALAP scheduling is used to determine the possible control steps for each operation. A force is then calculated for the scheduling of each operation into each possible control step this force is based on the operation, the control step, and the available functional units. The operation / control step pair with the most-negatively-value force is then chosen, and bound to the functional unit with the lowest instance cost and connection compatibility. 

Force-Directed Scheduling in Automatic Data Path Synthesis. 

The scheduling approach in HIS differs from most scheduling techniques traditionally used in high-level synthesis (e.g., list scheduling [21], force-directed scheduling [35]). HIS uses As-Fast-As-Possible (AFAP) scheduling [11] for... 

One commonly used approach is a list scheduling (LS) technique [1] where a hardware constraint is specified and the algorithm attempts to minimize the total execution time by using a local priority function to defer operations when resource conflicts occur. A different sjppTOxh,force-directed scheduling (FDS),... 

Figure 7. a) List schedule using urgency, and b) force-directed schedule for a simple example. 

In force-directed list scheduling (FDLS), the approach is similar except that force is used as the priority function. More precisely, whenever a hardware constraint is exceeded in the course of regular scheduling, force calculations are used to... 

Application To Force-Directed Scheduling HAL Data Structures for Control Flow ... 

The data stractures used in the HAL system to represent control blocks support the movement of dataflow operations across control boundaries in a very natural fashion. These data structures allow us to make use of the force-directed scheduling framework directly, even in the ivesence of complex conditionals. 

For applications where it is important to minimize the average time required to execute multiple iterations of a behavior containing conditional blocks, a mechanism must be included to minimize the length of the shorter branches in a control block. This occurs naturally in force-directed list scheduling (FDLS) since operations are assigned ASAP, shbject to resource limitations. If a branch is shorter than its counterpart, then we simply can strip the NOPs between the last data flow operation and the beginning of the join operation. 

The force-directed scheduling framework also supports two forms of pipelining functional pipelining [10], [11] and structural pipelining [12]. 

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