void replicate0(const EncryptedArray& ea, Ctxt& ctxt, long pos)
{
long dim = ea.dimension();
for (long d = 0; d < dim; d++) {
if (!ea.nativeDimension(d)) {
long shamt = -ea.coordinate(d, pos);
ea.rotate1D(ctxt, d, shamt, true); // "don't care"
}
Ctxt ctxt_orig = ctxt;
long sz = ea.sizeOfDimension(d);
long k = NumBits(sz);
long e = 1;
// now process bits k-2 down to 0
for (long j = k-2; j >= 0; j--) {
// e -> 2*e
Ctxt tmp = ctxt;
ea.rotate1D(tmp, d, e, true); // "don't care"
ctxt += tmp;
e = 2*e;
long b = bit(sz, j); // bit j of sz
// e -> e+b
if (b) {
ea.rotate1D(ctxt, d, 1, true); // "don't care"
ctxt += ctxt_orig;
e++;
}
}
}
}
// selects range of slots [lo..hi) in dimension d
static
void SelectRangeDim(const EncryptedArray& ea, ZZX& mask, long lo, long hi,
long d)
{
long nSlots = ea.size();
assert(d >= 0 && d < ea.dimension());
assert(lo >= 0 && lo <= hi && hi <= ea.sizeOfDimension(d));
vector<long> maskArray;
maskArray.resize(nSlots);
for (long i = 0; i < nSlots; i++) {
long c = ea.coordinate(d, i);
if (c >= lo && c < hi)
maskArray[i] = 1;
else
maskArray[i] = 0;
}
ea.encode(mask, maskArray);
}
// recursiveReplicateDim:
// d = dimension
// ea.sizeOfDimension(d)/2 <= extent <= ea.sizeOfDimension(d),
// only positions [0..extent) are non-zero
// 1 <= 2^k <= extent: size of current interval
// 0 <= pos < ea.sizeOfDimension(d): relative position of first vector
// 0 <= limit < ea.sizeOfDimension(): max # of positions to process
// dimProd: product of dimensions 0..d
// recBound: recursion bound (controls noise)
//
// SHAI: limit and extent are always the same, it seems
static
void recursiveReplicateDim(const EncryptedArray& ea, const Ctxt& ctxt,
long d, long extent, long k, long pos, long limit,
long dimProd, long recBound,
RepAuxDim& repAux,
ReplicateHandler *handler)
{
if (pos >= limit) return;
if (replicateVerboseFlag) { // DEBUG code
cerr << "check: " << k; CheckCtxt(ctxt, "");
}
long dSize = ea.sizeOfDimension(d);
long nSlots = ea.size();
if (k == 0) { // last level in this dimension: blocks of size 2^k=1
if ( extent >= dSize) { // nothing to do in this dimension
replicateAllNextDim(ea, ctxt, d+1, dimProd, recBound, repAux, handler);
return;
} // SHAI: Will we ever have extent > dSize??
// need to replicate to fill positions [ (1L << n) .. dSize-1 ]
if (repAux.tab(d,0).null()) { // generate mask if not there already
ZZX mask;
SelectRangeDim(ea, mask, 0, dSize - extent, d);
repAux.tab(d, 0).set_ptr(new DoubleCRT(mask, ea.getContext()));
}
Ctxt ctxt_tmp = ctxt;
ctxt_tmp.multByConstant(*repAux.tab(d, 0));
ea.rotate1D(ctxt_tmp, d, extent, /*don't-care-flag=*/true);
ctxt_tmp += ctxt;
replicateAllNextDim(ea, ctxt_tmp, d+1, dimProd, recBound, repAux, handler);
return;
}
// If we need to stop early, call the handler
if (handler->earlyStop(d, k, dimProd)) {
handler->handle(ctxt);
return;
}
k--;
Ctxt ctxt_masked = ctxt;
{ // artificial scope to miminize storage in the recursion
{ // another artificial scope (SHAI: this seems redundant)
// generate mask at index k+1, if not there yet
if (repAux.tab(d, k+1).null()) { // need to generate
vector< long > maskArray(nSlots,0);
for (long i = 0; i < nSlots; i++) {
long c = ea.coordinate(d, i);
if (c < extent && bit(c, k) == 0)
maskArray[i] = 1;
}
// store this mask in the repAux table
ZZX mask;
ea.encode(mask, maskArray);
repAux.tab(d, k+1).set_ptr(new DoubleCRT(mask, ea.getContext()));
}
// Apply mask to zero out slots in ctxt
ctxt_masked.multByConstant(*repAux.tab(d, k+1));
}
Ctxt ctxt_left = ctxt_masked;
ea.rotate1D(ctxt_left, d, 1L << k, /*don't-care-flag=*/true);
ctxt_left += ctxt_masked;
recursiveReplicateDim(ea, ctxt_left, d, extent, k, pos, limit,
dimProd, recBound, repAux, handler);
}
pos += (1L << k);
if (pos >= limit)
return;
Ctxt ctxt_right = ctxt;
ctxt_right -= ctxt_masked;
ctxt_masked = ctxt_right; // reuse ctxt_masked as a temp
ea.rotate1D(ctxt_masked, d, -(1L << k), /*don't-care-flag=*/true);
ctxt_right += ctxt_masked;
recursiveReplicateDim(ea, ctxt_right, d, extent, k, pos, limit,
dimProd, recBound, repAux, handler);
}
