Resolviendo ejercicios de MPI (y tambien en erlang) Parte 4

Sigo molestando con estos problemas, me salte uno que no me daba ganas de resolver y pase al siguiente:

http://www.mcs.anl.gov/research/projects/mpi/tutorial/mpiexmpl/src/ring/C/main.html

Write a program that takes data from process zero and sends it to all of the other processes by sending it in a ring. That is, process i should receive the data and send it to process i+1, until the last process is reached.

la solucion en C salio bastante facil haciendo copypasta de los problemas anteriores y sorprendentemente en este caso los otros procesos si imprimieron a la consola:

#include <stdio.h>
#include <mpi.h>

int main (int argc, char** argv) {
 int rank, size, value, i;
 MPI_Status status;

 MPI_Init (&argc, &argv);   /* starts MPI */
 MPI_Comm_rank (MPI_COMM_WORLD, &rank);        /* get current process id */
 MPI_Comm_size (MPI_COMM_WORLD, &size);        /* get number of processes */

 do {
  if(rank == 0) {
   printf("give me a value: ");
   scanf("%d", &value);
   fflush(stdout);
   MPI_Send(&value, 1, MPI_INT, rank + 1, 1, MPI_COMM_WORLD);
  }
  else{
   MPI_Recv(&value, 1, MPI_INT, rank - 1, 1, MPI_COMM_WORLD, &status);
   printf("process %d received %d\n", rank, value);
   if(rank + 1 < size) {
    printf("sending to %d\n", rank + 1, value);
    MPI_Send(&value, 1, MPI_INT, rank + 1, 1, MPI_COMM_WORLD);
   }
   fflush(stdout);
  }
 } while(value >= 0);
 printf("negative value, closing\n");

 MPI_Finalize();
 return 0;
}

la solucion en erlang (tambien robando del ejercicio anterior):

-module(ej5).
-export([run/1]).

run(Total) ->
 NextPid = spawn_listeners(Total),
 get_values(NextPid).

spawn_listeners(Count) -> spawn_listeners(Count, none).

spawn_listeners(0, NextPid) -> NextPid;
spawn_listeners(Count, LastPid) ->
 NextPid = spawn(fun() -> listener(LastPid) end),
 spawn_listeners(Count - 1, NextPid).

listener(NextPid) ->
 receive
  Int -> 
   io:format("process ~p received ~p~n", [self(), Int]),
   if
    NextPid /= none -> 
     io:format("sending to ~p~n", [NextPid]),
     NextPid ! Int;
    true -> ok
   end,
   if 
    Int >= 0 -> listener(NextPid);
    true -> 
     io:format("negative value, closing ~p~n", [self()])
   end
 end.

get_value(Message, ConversionFun) ->
 case io:get_line(Message) of 
  {error, Reason} -> {error, Reason};
  eof -> {error, eof};
  Value -> ConversionFun(Value)
 end.

get_values(NextPid) ->
 case get_value("give me an int value (negative to quit): ", fun(Val) -> string:to_integer(Val) end) of
  {error, Reason} ->
   io:format("error reading int value (~p)~n", [Reason]),
   get_values(NextPid);
  {IntValue, _Rest} ->
   io:format("sending to ~p~n", [NextPid]),
   NextPid ! IntValue,
   if 
    IntValue >= 0 -> get_values(NextPid);
    true -> io:format("negative value, closing~n")
   end
 end.

ejemplo de salida:

$ erl
Erlang (BEAM) emulator version 5.6.5 [source] [async-threads:0] [kernel-poll:false]

Eshell V5.6.5 (abort with ^G)
1> c(ej5).
{ok,ej5}
2> ej5:run(3).
give me an int value (negative to quit): 3
sending to <0.40.0>
process <0.40.0> received 3
sending to <0.39.0>
process <0.39.0> received 3
sending to <0.38.0>
process <0.38.0> received 3
give me an int value (negative to quit): asd
error reading int value (no_integer)
give me an int value (negative to quit): 42
sending to <0.40.0>
process <0.40.0> received 42
sending to <0.39.0>
process <0.39.0> received 42
sending to <0.38.0>
process <0.38.0> received 42
give me an int value (negative to quit): -1
sending to <0.40.0>
negative value, closing
process <0.40.0> received -1
sending to <0.39.0>
ok
negative value, closing <0.40.0>
process <0.39.0> received -1
sending to <0.38.0>
negative value, closing <0.39.0>
process <0.38.0> received -1
negative value, closing <0.38.0>