Generating Primes and the O'Neill paper, my final version, critique welcome

[Angel Alvarez]

Hi

This a my final version on erlang for the  O'Neill paper and the message from 
James Aimonetti.

Ive include synchronous calls between workers to avoid filling up mailboxes.
code is very barebones to keep it simple if anyone wants to see how it works :-P

I hope James will find it interesting and iwll be much pleased to ear any advices
from the gurus on this code.



/Angel 
-- 
No imprima este correo si no es necesario. El medio ambiente está en nuestras manos.
__________________________________________

Clist UAH a.k.a Angel
__________________________________________
Money is a good standard. Micro$oft.
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% "Genuine" Erathostenes sieve in erlang
% based on http://www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf
% 2009 Angel Alvarez
%
% Process  1     2     3     4     5     6     7 ....
%       
%         02    03    05    07    11    13    17
% P 02 -> 04
% P 03    04 -> 09
% C 04 == 04    09
% P 05    06    09 -> 25
% C 06 == 06    09    25
% P 07    08    09    25 -> 49
% C 08 == 08    09    25    49
% C 09    10 == 09    25    49
% C 10 == 10    12    25    49
% P 11    12    12    25    49 -> 121
% C 12 == 12    12    25    49    121
% P 13    14    15    25    49    121 -> 169
% C 14 == 14    15    25    49    121    169
% C 15    16 == 15    25    49    121    169
% C 16 == 16    18    25    49    121    169
% P 17    18    18    25    49    121    169 -> 289

-module(multi_erathostenes).
-author("angel@REDACTED").
-compile(export_all).

compare(X,Y) when X > Y -> greater;
compare(X,Y) when X < Y -> smaller;
compare(_,_) -> equal.


worker(Prime,UpperBound)->
	receive
		{test,Number,ParentPID} ->
			ParentPID ! ok,
			case compare(Number,UpperBound) of
				equal ->
%					io:format("[Worker of prime: ~w (~w)] Found composite: ~w~n",[Prime,UpperBound,Number]),
					worker(Prime,UpperBound + Prime);
				smaller ->
					io:format("[Worker of prime: ~w (~w)] Spawn new worker for Prime: ~w~n",[Prime,UpperBound,Number]),
					NextPID =spawn(?MODULE,worker,[Number,Number*Number]),
					worker(Prime,UpperBound,NextPID)
			end;
		stop ->
		    noop
	end.

worker(Prime,UpperBound,NextPID) ->
	receive
		{test,Number,ParentPID} ->
			ParentPID ! ok,
			case compare(Number,UpperBound) of
				equal ->
%					io:format("[Worker of prime: ~w (~w)] Found composite: ~w~n",[Prime,UpperBound,Number]),
					worker(Prime,UpperBound + Prime,NextPID);
				smaller ->
% 					io:format("[Worker of prime: ~w (~w)] passing along: ~w~n",[Prime,UpperBound,Number]),
					NextPID ! {test,Number,self()}, 
					receive
					    ok -> ok
					end,
					worker(Prime,UpperBound,NextPID);
				greater ->
% 					io:format("[Worker of prime: ~w (~w)] passing along: ~w~n",[Prime,UpperBound,Number]),
					NextPID ! {test,Number,self()},
					receive
					    ok -> ok
					end,
 					worker(Prime,UpperBound+Prime,NextPID)
			end;
		stop ->
		    NextPID ! stop,
		    noop
	end.
start(N) ->
    OnePID=spawn(?MODULE,worker,[2,4]),
    cicle(3,N,OnePID).

cicle(Last,Last,Worker) ->
    Worker ! stop;
cicle(Current,Last,Worker) ->
    Worker ! {test,Current,self()},
    receive
	ok -> ok
    end,
    cicle(Current+1,Last,Worker).