MODULE exo2;
(* ----------------------------------------------------------------------
   exo2.pm
   D. Thiebaut
   Computes the max of a vector variable using data movement in the
   chain of PEs.
   ---------------------------------------------------------------------- *)

CONST N=8; (* # of PEs *)

(* ----------------------------------------------------------------------
   P A R A L L E L    A R C H I T E C T U R E
   ---------------------------------------------------------------------- *)
CONFIGURATION chain[0..N-1];
CONNECTION
    left:  chain[i]->chain[i-1];
    right: chain[i]->chain[i+1];


(* ----------------------------------------------------------------------
   V A R I A B L E S
   ---------------------------------------------------------------------- *)
VAR
    x       : chain OF INTEGER;
    y       : chain OF INTEGER;
    i       : INTEGER;


(* ----------------------------------------------------------------------
    M A I N
   ---------------------------------------------------------------------- *)
BEGIN
    (*--- initialize x with random #'s ---*)
    x := RandomInt( chain ) MOD 100;

    (*--- use y as a shift register    ---*)
    y := x;

    WriteString( "x = " );
    WriteInt( x, 2 );
    WriteString( "y = " );
    WriteInt( y, 2 );
    WriteLn;

    (*--- move data to the left, and keep largest of x and y in y ---*)
    (*--- as it is moving from right to left...                   ---*)
    FOR i:=1 TO N-1 DO

        (*--- move y to the left ---*)
        y := RECEIVE.left( y );

        WriteLn;
        WriteString( "x = " );
        WriteInt( x, 2 );
        WriteString( "y = " );
        WriteInt( y, 2 );

        (*--- keep largest of x and y in y ---*)
        IF x > y THEN
            y := x;
        END; (* IF *)

    END; (* FOR *)

    (*--- output ---*)
    WriteLn;
    WriteString( "largest = " );
    WriteInt( y<<1>>, 2 );

END exo2.