Coherent parallel C

ABSTRACT

Coherent Parallel C (CPC) is an extension of C for parallelism. The extensions are not simply parallel for loops; instead, a data parallel programming model is adopted. This means that one has an entire process for each data object. An example of an “object” is one mesh point in a finite element solver. How the processes are actually distributed on a parallel machine is transparent—the user is to imagine that an entire processor in a distributed-memory environment is dedicated to each process. This simplifies programming tremendously: complex if statements associated with domain boundaries disappear; problems which do not exactly match the machine size and irregular boundaries are all handled transparently.

The usual communication calls are not seen at all at the user level. Variables of other processes (which may or may not be on another processor) are merely accessed (global memory). The first pass of the CPC compiler schedules the necessary communications in an efficient, coherent manner. Processes in CPC are insulated from one another and interact in a deterministic manner. This allows tractable debugging. Standard C I/O is provided, with simple extensions for parallelism.

We currently have a CPC runtime system implemented on an NCUBE and have started implementing a true compiler for the language.

CPC is not specific to distributed memory machines. Implementation of this language on other architectures is natural—for example, there seems to be no fundamental problem with CPC on shared-memory parallel computers.

References

1. Chow87.E. Chow, H. Madan, and J. Peterson, "A Real-Time Adaptive Message Routing Network for the Hypercube Corn= purer," Caltech Concurrent Comput~ tion Program ~eport C3P-469, 1987.
2. Dall86.W. Dally and C. Seits, "A VLSI Architecture for Concurrent Data Structures," Y. Distributed Systems I (1986), 187.
3. Dull88.W. Dally, "Fine-Grain Message-Passing Concurrent Computers," this volume.
4. DAP79."The DAP Approach," in Infotech Slate of ~he Art Report: S~percomputers, 2, edited by C.R. J esshop=, R.W. Hockney, Infotech Intl. Ltd., Maidenhead (1979), 311-29.
5. Denn74.J.B. Dennis, "First Version ofa Datafiow Procedure Language," in Proc. Prograra~ing Syraposi~m, Paris 1974, edited by, G. Goos and J. Hartmanis, Springer- Verlag, New York (1974).
6. Felt85.E.W. Felten, S.C. Karlin, and $.W. Otto, "Sorting on a Hypercube," Caltech Concurrent Computation Program report C3P-244.
7. Felt88.E.W. Felten and S.W. Otto, "Chess on a Hypercube," this volume.
8. Fox88a.G.C. Fox, "What Have We Learned from Using Real Parallel Machines to Solve Real Problems?" in this volume.
9. Fox88b.G.C. Fox, M.A. Johnson, G.A. Lyzenga, S.W. Otto, J.K. Salmon, and D.W. Walker, "Solving Problems on Concurrent Processors", Prentice Hall, New Jersey 1988.
10. Harb87.S.P. Harbison and G.L. Steele, Jr., "C: A R. eference Manual," Prentice Hall, New Jersey, 1987.
11. Hill85.W.D. Hfilis, "The Connection Machine," MIT Press, Cambridge, 1985.
12. NCUB87."NCUBE Reference Manual," NCUBE Corporation, 1987.
13. Quin88.M.J. Quinn, P.J. Hatcher, K.C. lourdenais, "Compiling C* Programs for a Hypercube Multicomputer," this volume.
14. Rose87.J. Rose, G. Steele, "C*: An Extended C Language for Data Parallel Programming,'' Thinking Machines Technical Report PL87-5 (1987)
15. Salm87.S. Salmon, "CUBIX: Programming Hypercubes Without Programming Hosts," in Hype~cu& Mtdtiprocessors i987, edited by M. Heath, SIAM (1987), 3, Caltech Concurrent Computation Program report C3P-378.
16. Stro86.B. Stroustrup, "The C++ Programming Language," Addison Wesley, Reading, Mass., 1986.

Index Terms

• Computer systems organization

  • Architectures

    • Parallel architectures

      • Multiple instruction, multiple data

• Computing methodologies

  • Concurrent computing methodologies

    • Concurrent programming languages

• Networks

  • Network architectures

• Software and its engineering

  • Software notations and tools

    • General programming languages

      • Language types

        • Concurrent programming languages

  • Software organization and properties

    • Contextual software domains

      • Operating systems