S. H. Yuang, Y. L. Jeang, C. T. Hwang, Y. C. Hsu, J. F. Wang, "A Tree-Based Scheduling Algorithm for Control-Dominated Circuits", In Proc. of the 30th ACM/IEEE Design Automation Conference, pp 578-582, June, 1993.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....India, Jan. 3 6, 1996. 18] J. berg, P. Eles, A. Hemani, K. Kuchcinski, Z. Peng, Specifying Local Timing Constraints for HLS of Digital Systems in VHDL . In Proc of the 3rd Asian Pacific Conference on Hardware Description Languages (APCHDL 96) pp 145 149, Bangalore, India, Jan. 8 11, 1996. [19] P. Ellervee, A. Hemani, A. Kumar, B. Svantesson, J. berg, H. Tenhunen, Controller Synthesis in Control and Memory Centric High Level Synthesis System , In Proc. of the 5th Biennial Baltic Electronic Conference, pp 393 396, Tallinn, Estonia, Oct. 7 11, 1996. 20] F. Bueno, J. berg, A. Kumar, M. ....

....units. In telecommunication systems, targeted for routing, switching etc. the functionality is dominated by control decision and interactions with memory, with little or no arithmetic operations. There has been several suggestions on how to extend HLS to cope with control dominated functionality [17, 18, 19, 20, 21, 22]. While the work by W. Wolf [17] presents a model for performing behavioural synthesis, the other papers address the problem of global scheduling of the of the datapath operations into control states. Figure 1.4. The principles of High Level Synthesis X(15 downto 1) X(14 downto 0) Xin; ....

S. H. Yuang, Y. L. Jeang, C. T. Hwang, Y. C. Hsu, J. F. Wang, "A Tree-Based Scheduling Algorithm for Control-Dominated Circuits", In Proc. of the 30th ACM/IEEE Design Automation Conference, pp 578-582, June, 1993.

....power minimization. Most of the synthesis systems described above worked primarily on datapath dominated circuits where the effect of control nodes was negligible. Many researches have attempted to relax this assumption and proposed high level synthesis systems towards control dominated designs [32], 33] 34] 28] 29] 13] The most notable work towards providing synthesizability for control intensive designs is IMPACT [70] which is geared for power optimization. Their methodology is also based on SCALP with some generalizations for handling control. They use behavioral simulation to ....

S.H. Huang, Y.L. Jeang, C.T. Hwang, Y.C. Hsu and J.F. Wang . " A Tree Based Scheduling Algorithm for Control Dominated Circuits ". In Design Automation Conference, pages 578--582, Jun 1993.

....following the AFAP strategy, and finally merg 72 es all different paths into one Finite State Machine (FSM) The main drawback of the approach is the need to evaluate all possible paths, which number can be enormous. Different improvements have been made to reduce the number of paths [BRN97] HLH93] and to improve loop scheduling [BDB94] ROJ94] YeWo96] Several schedulers have been developed for High Level Synthesis of control dominated systems but there is no scheduler which solves the problem comprehensively and efficiently, considering all the relevant issues operation chaining, ....

....reordered or parallelized. Thus, the solution is optimal only for the given order of operations. Another drawback of this approach is that a vast amount of time and space is required to enumerate all possible paths. The problem of path explosion in PBS is somewhat reduced in tree based scheduling [HLH93] which also produces an as fast as possible schedule for all paths. The rooted tree used here to represent the collection of paths is more compact as compared to considering all the paths individually, but can still be exponentially large. The tree based scheduler considers data dependencies and ....

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S. H. Huang, Y. L. Jeang, C. T. Hwang, Y. C. Hsu, J. F. Wang, "A Tree-Based Scheduling Algorithm for Control-Dominated Circuits", Proc. of 30th ACM/IEEE Design Automation Conference, pp. 578-582, June 1993.

....in section 1.1. In summary, the scheduling scope includes: operand dependencies, controldependent behavior, sequential behavior and constraints, hardware resource constraints, repeating behavior, completeness and quality. Heuristic scheduling techniques are by far the most common [22] 25] 44] 45][58][68] 71] 104] 109] 110] 121] 132] 133] 134] All heuristics, and in fact all scheduling techniques, address operand dependencies. If a scheduling technique only considers operand dependencies, then it only schedules data flow graphs, DFGs. Within the DFG paradigm, there is considerable work ....

S. H. Huang, et al.. "A Tree-Based Scheduling Algorithm for Control Dominated Circuits", Proc. 30th ACM/IEEE Design Automation Conf., pp. 578582, Dallas, USA, June 1993.

....by transforming a set of algorithms on the source code level as it has been illustrated with the example code in figure 2 and 3. Each of the compilers follows a different loop optimization strategy: The C60 compiler uses loop pipelining, whereas the TriMedia compiler generates decision trees [9] for scheduling, a technique which is basically a generalization of loop unrolling. Although MPP was developed for loop pipelining, it was possible to achieve improvements with the TriMedia compiler as well. Still, on both systems the application of MPP on the source code level did not allow for ....

S. H. Huang, Y. L. Jeang, C. T. Hwang, Y. C. Hsu, and J. F. Wang. A tree-based scheduling algorithm for control-dominated circuits. In DAC, pages 578--582, 1993.

.... condition, the so called basic block (BB) As such a local approach may lead to poor quality results for control flow dominated designs, operations can be moved up and down after BB scheduling [2] Other approaches have focused on scheduling operations directly across BB boundaries [4] 3] [5], 6] 7] However, an optimal solution might be missed either due to the applied heuristics [3] 5] 6] 7] or due to a fixed order chosen in advance [4] A symbolic technique was presented to cope with control dependent scheduling [1] Instead of generating a single representative solution ....

.... for control flow dominated designs, operations can be moved up and down after BB scheduling [2] Other approaches have focused on scheduling operations directly across BB boundaries [4] 3] 5] 6] 7] However, an optimal solution might be missed either due to the applied heuristics [3] [5], 6] 7] or due to a fixed order chosen in advance [4] A symbolic technique was presented to cope with control dependent scheduling [1] Instead of generating a single representative solution (like the men On leave from INE, Federal University of Santa Catarina, Brazil and partially supported ....

[Article contains additional citation context not shown here]

S. Huang et al., "A tree-based scheduling algorithm for control dominated circuits," in Proc. ACM/IEEE DAC, pp. 578-582, 1993.

....whole PBS technique. Consequently, although reordering improves the handling of more complex data flow, the method cannot support speculative execution, which limits the exploitation of par 7 allelism with complex control flow [19] This limitation is released in tree based scheduling (TBS) [15], where speculative execution is allowed and the AFAP approach is conserved by keeping all paths on a tree. However, since the notion of interval is lost, a list scheduler is used to fill states with operations. Condition vector list scheduling (CVLS) 31] allows code duplication and supports ....

....that assignments represent a relative time encoding. The absolute time is control dependent and it is given by the instant when BB v starts executing plus the value in attribute begin. Handling redundancies. Operations may be redundant for some paths in a behavioral description as shown in [15]. In our method, such redundancies are eliminated during the generation of initial links. Operation b in figure 4, for instance, will only be linked to BB C, even though it was originally described in BB A, as if it belonged to both paths. TBS [15] uses tree optimization to remove redundancies by ....

[Article contains additional citation context not shown here]

S.Huang et al., "A tree--based scheduling algorithm for control dominated circuits," in Proc.ACM/IEEE Design Automation Conference, pp--578--58, 1993.

....is well suited for control flow dominated applications. The basic principle is to minimize the total execution time by taking into account the di#erent possible paths. The drawback of this method is that a predefined order of execution must be enforced before scheduling. In tree based scheduling [3], this limitation is released by keeping all paths on a tree. Wakabayashi [14] 15] uses a condition vector to identify mutually exclusive operations and proposes a list scheduling method based on this condition vector to deal with single nested conditional branches. Kim et al. 5] 6] transfer a ....

S.H. Huang, Y.L. Jeang, C.T. Huang, Y.C. Hsu, and J.F. Wang , A Tree-Based Scheduling Algorithm for ControlDominated Circuits, Proc. Conf. on Design, Automation and Test, 1993.

....which is a C select implementation. In C select implementation, the operations in conditional branches cannot be executed until the corresponding condition is resolved. Many scheduling algorithms in the recent literature allow execution of branch operations before the corresponding conditional [24, 23, 26, 27]. This is known as speculative execution and is shown to produce faster schedules on many benchmarks [27] Our estimation method can support both C select implementation and speculative execution. In C select implementation, the control precedences are treated the same way as data dependencies are ....

S.H.Huang, et. al., "A Tree-Based Scheduling Algorithm For Control-Dominated Circuits", 30th Design Automation Conference, 1993.

.... SMG with best schedule length takes at least one order of magnitude less than the method in [11] More experimental results can be found in [13] TABLE I COMPARISON WITH OTHER HLS METHODS waka kim maha parker add 1 2 1 2 1 2 sub 1 1 1 3 1 3 cmp 1 1 ours 7 6 5 4 5 4 ST[11] 7 6 5 4 4 TBS[8] 7 5 CVLS[15] 7 6 5 4 5 4 HRA[9] 7 7 8 VI. RELATED WORK AND CONCLUSIONS Some HLS methods for control flow dominated applications do not support speculative execution at all [2] 9] Our support for speculative execution is more general than most related HLS methods: although the ....

.... execution is more general than most related HLS methods: although the first form of speculative execution described in Section III is allowed in 104 TABLE II COMPARISON WITH AN EXACT METHOD rotor s2r alu 1 2 3 4 1 2 3 4 3 mul 0 0 0 0 2 2 2 2 2 ours 12 7 7 6 10 8 8 8 8 ST[11] 12 7 7 6 10 8 8 8 8 [8] [11] 15] the second form of speculative execution is either not supported or neglected. In particular, the method reported in [11] which also relies on Boolean manipulation, is limited by the model adopted for scheduling. In that approach, a linear time sequence of time steps is employed in ....

S. Huang et al., "A tree-based scheduling algorithm for control dominated circuits," in Proc. ACM/IEEE Design Automation Conference, pp. 578-582, 1993.

....that scheduling is cast as a clique covering problem on an interval graph, code motions resulting in speculative execution are not allowed. Thus, the method has limited capability of exploiting parallelism with complex control flow [13] This limitation is released in tree based scheduling (TBS) [10], by allowing boosting and duplication code motions. Condition vector list scheduling (CVLS) 18] allows code motion and supports speculative execution. However, the underlying mutual exclusion representation is limited [1] In Trace scheduling (TS) 6] a main path (trace) is chosen to be ....

....u in BB v) c) end (completion time of u in BB v) Assignments represent a relative time encoding. The absolute time is given by the instant BB v starts execution plus the value in attribute begin. Freedom for code motion: Operations may be redundant for some paths in a behavioral description [10]. TBS uses tree optimization to remove redundancies by propagating each operation to the latest BB where it is to be used. CVLS eliminates them by using extended condition vectors [18] Even though they remove redundancies, those methods don t succeed to encode the freedom for code motion. Tree ....

[Article contains additional citation context not shown here]

S.Huang et al., "A tree--based scheduling algorithm for control dominated circuits," in Proc. ACM/IEEE DAC'93, pp--578--582

....These control dependencies seriously limit the potential parallelism. While early scheduling algorithms focused on the problem to distribute operations within a basic block emphasis has, meanwhile, shifted to scheduling across basic block boundaries. Path based scheduling ( 3] improved in [4, 5]) schedules paths of an execution rather than basic blocks, but it does not solve the problem of control dependencies. Speculative computation (SC) potentially reduces the control dependencies by allowing to execute an operation before it is known to be necessary. It is used in percolation ....

S. Huang, Y. Jeang, et. al., "A Tree-Based Scheduling Algorithm For Control-Dominated Circuits", DAC, pp. 578-582, 1993.

....for CMIST has to deal with data flow as well as control flow. The need to consider control flow as well as data flow makes the CMIST scheduling essentially global and hence more complex. Recent years have seen development of some new techniques for scheduling of control dominated circuits [2, 3, 4]. All these aim at globally scheduling the operations (control as well as data) into control states followed by generation of an FSM based controller. Path based scheduling was introduced by [2] as a mechanism to do global scheduling. In this method, all control flow paths are identified and ....

....in different control steps. However, the main drawback of this approach is the enumeration of all possible paths in the control flow graph, which can potentially result in combinatorial explosion. The problem of path explosion in path based scheduling is somewhat reduced in tree based scheduling [3] which also produces an as fast as possible schedule for all paths. The rooted tree used here to represent the collection of paths is more compact as compared to considering all the paths individually, but can still be exponentially large. Unlike the path based scheduler, the tree based scheduler ....

S.H.Huang, Y.L.Jeang, C.T.Hwang, Y.C.Hsu, J.F.Wang. A Tree-Based Scheduling Algorithm for Control-Dominated Circuits. Proceedings of the 30th ACM/IEEE Design Automation Conference, pp.578-582, ACM/IEEE, June 1993.

....demonstrate the relevanceand effectiveness of both the performance measure and the scheduling algorithm. I. INTRODUCTION Several existing scheduling algorithms specifically target behavioral specifications containing a large number of mutually exclusive paths due to the presence of conditionals [1, 2, 3, 4, 5, 6]. The following metrics are used to evaluate the performance of the schedules generated by these algorithms: 1) the number of clock cycles required to execute the longest and shortest paths (LP SP) and (2) the number of clock cycles required, averaged over all paths in the description. These ....

S.H. Huang, Y.L. Jeang, C.T. Hwang, Y.C. Hsu, and J.F. Wang. A Tree-Based Scheduling Algorithm For Control-Dominated Circuits. In Proc. of the 30th ACM/IEEE DAC, 1993.

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