```// ************************************************************************** //
//                                                                            //
//    eses                   eses                                             //
//   eses                     eses                                            //
//  eses    eseses  esesese    eses   Embedded Systems Group                  //
//  ese    ese  ese ese         ese                                           //
//  ese    eseseses eseseses    ese   Department of Computer Science          //
//  eses   eses          ese   eses                                           //
//   eses   eseses  eseseses  eses    University of Kaiserslautern            //
//    eses                   eses                                             //
//                                                                            //
// ************************************************************************** //
// The following module implements a multiplication of B-complement numbers.  //
// The computation is done by summing up the usual partial products by the use//
// of carry-save adders for the intermediate steps and a carry-ripple adder   //
// for the final step.                                                        //
// The depth of the circuit is seen by observing that the evaluation can      //
// proceed row-wise for i=0..M-2, and columnwise for the final row. Thus, the //
// depth of the circuit is O(M+N) and therefore not optimal.                  //
// ** Note: We are only interested in even values of B **                     //
// ************************************************************************** //

macro B = 4;    // base of the radix numbers
macro M = 4;    // number of digits used
macro N = 3;    // number of digits used

macro alpha(x) = (x<(B/2) ? +x : +x-B);
macro gamma(y) = (y<0 ? y+B : y);
macro dval(x,i,k) = (i==k-1 ? alpha(x[i]) : +x[i]);
macro intval(x,k) = sum(i=0..k-1) (dval(x,i,k) * exp(B,i));

module IntMulCSACRA([M]nat{B} ?x,[N]nat{B} ?y,[M+N]nat{B} p) {
event [M][N]nat{B} pp;      // digits of partial products
event [M][N]int{B} cp;      // carries for summation in CSA array
event [N]int{2} cr;         // carries for summation in final CRA
assert(B==2*(B/2));         // check that B is even
// -------------------------------------------------------------------------
// this part has depth O(M) since each row can be evaluated in O(1)
// -------------------------------------------------------------------------
for(i=0..M-1) {
for(j=0..N-1)
// pp[i][N..0] = pp[i-1][N-1..1] + cp[i-1][N-1..0] + x[i]*y[N-1..0]
let(xin = (i==M-1 ? alpha(x[i]) : +x[i]))
let(yin = (j==N-1 ? alpha(y[j]) : +y[j]))
let(pin = (i==0 ? 0 : (j==N-1 ? 0 : pp[i-1][j+1])))
let(cin = (i==0 ? 0 : cp[i-1][j])) {
event int{B*B} sm;
sm = xin * yin + pin + cin;
cp[i][j] = sm / B;
pp[i][j] = sm % B;
}
}
// -------------------------------------------------------------------------
// final addition p[M+N-1..M] = pp[M-1][N-1..1] + cp[M-1][N-1..0] using CRA
// -------------------------------------------------------------------------
for(k=0..M-1) p[k] = pp[k][0];
for(j=0..N-1)
let(pin = (j==N-1 ? 0 : pp[M-1][j+1]))
let(cin = (j==0 ? 0 : cr[j-1])) {
event int{2*B} sm;
sm = pin + cp[M-1][j] + cin;
cr[j] = sm / B;
p[M+j] = (j==N-1 ? gamma(sm % B) : sm % B);
}
// -------------------------------------------------------------------------
// check the result
// -------------------------------------------------------------------------
assert(intval(p,M+N) == intval(x,M) * intval(y,N));
}
drivenby MinInt_MinInt {
x[M-1] = B/2;
for(i=0..M-2)
x[i] = 0;
y[N-1] = B/2;
for(i=0..N-2)
y[i] = 0;
}
drivenby MinInt_MaxInt {
x[M-1] = B/2;
for(i=0..M-2)
x[i] = 0;
y[N-1] = (B/2)-1;
for(i=0..N-2)
y[i] = B-1;
}
drivenby MaxInt_MinInt {
x[M-1] = (B/2)-1;
for(i=0..M-2)
x[i] = B-1;
y[N-1] = B/2;
for(i=0..N-2)
y[i] = 0;
}
drivenby MaxInt_MaxInt {
x[M-1] = (B/2)-1;
for(i=0..M-2)
x[i] = B-1;
y[N-1] = (B/2)-1;
for(i=0..N-2)
y[i] = B-1;
}
drivenby Test01 {
for(i=0..M-1)
x[i] = (-B/2-(i+1)) % B;
for(i=0..N-1)
y[i] = (-B/2-(i+1)) % B;
}
drivenby Test02 {
for(i=0..M-1)
x[i] = (-B/2-(i+1)) % B;
for(i=0..N-1)
y[i] = (-B-1-i) % B;
}
drivenby Test03 {
for(i=0..M-1)
x[i] = (-B-1-i) % B;
for(i=0..N-1)
y[i] = (-B/2-(i+1)) % B;
}
drivenby Test04 {
for(i=0..M-1)
x[i] = (-B-1-i) % B;
for(i=0..N-1)
y[i] = (-B-1-i) % B;
}
```