added MPI_Bcast

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@357 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

library/mpi/examples/demo1.pl

@@ -16,6 +16,7 @@ calc( From, To, Acc, Res ) :- !,
 
 %%
 %% This spreads the work among the processors
+%% and collects the results.
 %%
 
 do(0, Num) :-

library/mpi/examples/demo2.pl

@@ -0,0 +1,42 @@
+%% demo2.pl -- Stasinos Konstantopoulos
+%% konstant@let.rug.nl, Tue Feb 12 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 ).
+
+
+%%
+%% We'll pretend the preprocessing was more complicated, and have the
+%% root broadcast how many numbers each processor should do.
+%% Each processor must then figure out which ones to do and call calc/4.
+%%
+
+do(0, Num) :-
+	!,
+	mpi_bcast( Num, 0 ),
+	format( 'Proc 0: broadcast ~q.~n', [Num] ).
+do(Rank, _) :-
+	!,
+	mpi_bcast( Num, 0 ),
+	format( 'Proc ~q: had ~q broadcast from 0.~n', [Rank, Num] ).
+
+
+%%
+%% 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] ).