a first take at an interface to an MPI lib

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@354 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

library/mpi/examples/demo1.pl

@@ -0,0 +1,49 @@
+%% demo1.pl -- Stasinos Konstantopoulos
+%% konstant@let.rug.nl, Thu Jan 24 2002
+%%
+
+%%
+%% This the calculation that needs to be performed, in this case
+%% the sum of [From..To]
+%%
+
+calc( From, From, Acc, Res ) :- !,
+	Res is Acc + From.
+calc( From, To, Acc, Res ) :- !,
+	Acc1 is Acc + To,
+	To1 is To - 1,
+	calc( From, To1, Acc1, Res ).
+
+%%
+%% This spreads the work among the processors
+%%
+
+do(0, Num) :-
+	!,
+	Half is Num // 2,
+	format( 'Proc 0: Calculating ~q..~q~n', [1, Half] ),
+	calc( 1, Half, 0, R1 ),
+	format( 'Proc 0: Done! (~q)~n', [R1] ),
+	mpi_receive( R2, Source, Tag ), % Receive any Source, any Tag
+	format( 'Proc ~q said: ~q (Tag: ~q)~n', [Source,R2,Tag] ),
+	% mpi_receive( R2, 1, 1 ), % Be more particular
+	Res is R1 + R2,
+	format( 'Sum(1..~q) = ~q~n', [Num,Res] ).
+do(1, Num) :-
+	!,
+	Half is Num // 2,
+	format( 'Proc 1: Calculating ~q..~q~n', [Half,Num] ),
+	calc( Half, Num, 0, Res ),
+	format( 'Proc 1: Done! (~q)~n', [Res] ),
+	mpi_send( Res, 0, 1 ).
+
+
+%%
+%% This is the entry point
+%%
+
+start(Num) :-
+	mpi_open( Rank, NumProc, ProcName ),
+	format( 'Rank: ~q NumProc: ~q, ProcName: ~q~n', [Rank,NumProc,ProcName] ),
+	do( Rank, Num ),
+	format( 'Rank ~q finished!~n', [Rank] ).