A VHDL Specification of a Shared Memory Parallel Machine for Babel

W. Hans, J.J. Ruz, F. Saenz, St. Winkler

	   We present an abstract machine designed for the parallel
	   execution of functional logic programs, i. e. Babel. It is
	   accomplished utilizing a shared memory model. Efficiency
	   is gained by using the same stack mechanisms as the WAM,
	   i.e. the fast reclamation of memory during backtracking is
	   maintained despite the parallel extensions.

	   In addition to the strict behaviour of programs (e.g. in
	   Prolog), Babel offers non-strict functions that do not
	   necessarily demand all of the arguments for the evaluation. We
	   study the work load behaviour and the introduced restrictions
	   imposed by the insistence on the fast stack mechanisms. The
	   specification is carried out in the hardware description
	   language VHDL offering simulation facilities, and having a
	   temporal model which allows to gain	a performance study of
	   the parallel system. We present the results obtained from the
	   simulation of the VHDL specification, showing the speed-ups
	   gained with different numbers of processors.