ChooserPoly ChooserEvaluator::multiply_plain(const ChooserPoly &operand, int plain_max_coeff_count, const BigUInt &plain_max_abs_value)
{
if (operand.max_coeff_count_ <= 0 || operand.comp_ == nullptr)
{
throw invalid_argument("operand is not correctly initialized");
}
if (plain_max_coeff_count <= 0)
{
throw invalid_argument("plain_max_coeff_count must be positive");
}
if (plain_max_abs_value.is_zero())
{
return ChooserPoly(1, 0, new MultiplyPlainComputation(*operand.comp_, plain_max_coeff_count, plain_max_abs_value));
}
if (operand.max_abs_value_.is_zero())
{
return ChooserPoly(1, 0, new MultiplyPlainComputation(*operand.comp_, plain_max_coeff_count, plain_max_abs_value));
}
uint64_t growth_factor = min(operand.max_coeff_count_, plain_max_coeff_count);
int prod_bit_count = operand.max_abs_value_.significant_bit_count() + plain_max_abs_value.significant_bit_count() + get_significant_bit_count(growth_factor) + 1;
int prod_uint64_count = divide_round_up(prod_bit_count, bits_per_uint64);
Pointer prod_max_abs_value(allocate_zero_uint(prod_uint64_count, pool_));
ConstPointer wide_operand_max_abs_value(duplicate_uint_if_needed(operand.max_abs_value_.pointer(), operand.max_abs_value_.uint64_count(), prod_uint64_count, false, pool_));
multiply_uint_uint(&growth_factor, 1, plain_max_abs_value.pointer(), plain_max_abs_value.uint64_count(), prod_uint64_count, prod_max_abs_value.get());
ConstPointer temp_pointer(duplicate_uint_if_needed(prod_max_abs_value.get(), prod_uint64_count, prod_uint64_count, true, pool_));
multiply_uint_uint(wide_operand_max_abs_value.get(), prod_uint64_count, temp_pointer.get(), prod_uint64_count, prod_uint64_count, prod_max_abs_value.get());
return ChooserPoly(operand.max_coeff_count_ + plain_max_coeff_count - 1, BigUInt(prod_bit_count, prod_max_abs_value.get()), new MultiplyPlainComputation(*operand.comp_, plain_max_coeff_count, plain_max_abs_value));
}
ChooserPoly ChooserEvaluator::exponentiate(const ChooserPoly &operand, uint64_t exponent)
{
if (operand.max_coeff_count_ <= 0 || operand.comp_ == nullptr)
{
throw invalid_argument("operand is not correctly initialized");
}
if (exponent == 0 && operand.max_abs_value_.is_zero())
{
throw invalid_argument("undefined operation");
}
if (exponent == 0)
{
return ChooserPoly(1, 1, new ExponentiateComputation(*operand.comp_, exponent));
}
if (operand.max_abs_value_.is_zero())
{
return ChooserPoly(1, 0, new ExponentiateComputation(*operand.comp_, exponent));
}
// There is no known closed formula for the growth factor, but we use the asymptotic approximation
// k^n * sqrt[6/((k-1)*(k+1)*Pi*n)], where k = max_coeff_count_, n = exponent.
uint64_t growth_factor = static_cast<uint64_t>(pow(operand.max_coeff_count_, exponent) * sqrt(6 / ((operand.max_coeff_count_ - 1) * (operand.max_coeff_count_ + 1) * 3.1415 * exponent)));
int result_bit_count = static_cast<int>(exponent) * operand.max_abs_value_.significant_bit_count() + get_significant_bit_count(growth_factor) + 1;
int result_uint64_count = divide_round_up(result_bit_count, bits_per_uint64);
Pointer result_max_abs_value(allocate_uint(result_uint64_count, pool_));
util::exponentiate_uint(operand.max_abs_value_.pointer(), operand.max_abs_value_.uint64_count(), &exponent, 1, result_uint64_count, result_max_abs_value.get(), pool_);
ConstPointer temp_pointer(duplicate_uint_if_needed(result_max_abs_value.get(), result_uint64_count, result_uint64_count, true, pool_));
multiply_uint_uint(&growth_factor, 1, temp_pointer.get(), result_uint64_count, result_uint64_count, result_max_abs_value.get());
return ChooserPoly(static_cast<int>(exponent) * (operand.max_coeff_count_ - 1) + 1, BigUInt(result_bit_count, result_max_abs_value.get()), new ExponentiateComputation(*operand.comp_, exponent));
}
void exponentiate_uint_mod(const BigUInt &operand, const BigUInt &exponent,
const BigUInt &modulus, BigUInt &destination, const MemoryPoolHandle &pool)
{
if (operand.significant_bit_count() > modulus.significant_bit_count())
{
throw invalid_argument("operand is not reduced");
}
if (operand.is_zero() && exponent == 0)
{
throw invalid_argument("undefined operation");
}
if (!pool)
{
throw invalid_argument("pool is uninitialized");
}
if (operand.is_zero())
{
destination.set_zero();
return;
}
if (destination.bit_count() != modulus.significant_bit_count())
{
destination.resize(modulus.significant_bit_count());
}
ConstPointer operand_ptr = duplicate_uint_if_needed(operand, modulus.uint64_count(), false, pool);
util::exponentiate_uint_mod(operand_ptr.get(), exponent.data(), exponent.uint64_count(), Modulus(modulus.data(), modulus.uint64_count(), pool), destination.data(), pool);
}
ChooserPoly ChooserEvaluator::multiply_many(const vector<ChooserPoly> &operands)
{
if (operands.empty())
{
throw invalid_argument("operands vector can not be empty");
}
int prod_max_coeff_count = 1;
uint64_t growth_factor = 1;
int prod_max_abs_value_bit_count = 1;
vector<Computation*> comps;
for (vector<ChooserPoly>::size_type i = 0; i < operands.size(); ++i)
{
// Throw if any of the operands is not initialized correctly
if (operands[i].max_coeff_count_ <= 0 || operands[i].comp_ == nullptr)
{
throw invalid_argument("input operand is not correctly initialized");
}
// Return early if the product is trivially zero
if (operands[i].max_abs_value_.is_zero())
{
return ChooserPoly(1, 0, new MultiplyManyComputation(comps));
}
prod_max_coeff_count += operands[i].max_coeff_count_ - 1;
prod_max_abs_value_bit_count += operands[i].max_abs_value().significant_bit_count();
growth_factor *= (i == 0 ? 1 : min(operands[i].max_coeff_count_, prod_max_coeff_count));
comps.push_back(operands[i].comp_);
}
prod_max_abs_value_bit_count += get_significant_bit_count(growth_factor);
int prod_max_abs_value_uint64_count = divide_round_up(prod_max_abs_value_bit_count, bits_per_uint64);
Pointer prod_max_abs_value(allocate_zero_uint(prod_max_abs_value_uint64_count, pool_));
*prod_max_abs_value.get() = growth_factor;
for (vector<ChooserPoly>::size_type i = 0; i < operands.size(); ++i)
{
ConstPointer temp_pointer(duplicate_uint_if_needed(prod_max_abs_value.get(), prod_max_abs_value_uint64_count, prod_max_abs_value_uint64_count, true, pool_));
multiply_uint_uint(temp_pointer.get(), prod_max_abs_value_uint64_count, operands[i].max_abs_value_.pointer(), operands[i].max_abs_value_.uint64_count(), prod_max_abs_value_uint64_count, prod_max_abs_value.get());
}
return ChooserPoly(prod_max_coeff_count, BigUInt(prod_max_abs_value_bit_count, prod_max_abs_value.get()), new MultiplyManyComputation(comps));
}
void poly_eval_uint_mod(const BigPoly &poly_to_evaluate, const BigUInt &value, const BigUInt &modulus,
BigUInt &destination, const MemoryPoolHandle &pool)
{
if (poly_to_evaluate.significant_coeff_bit_count() > modulus.significant_bit_count())
{
throw invalid_argument("poly_to_evaluate is not reduced");
}
if (value.significant_bit_count() > modulus.significant_bit_count())
{
throw invalid_argument("value is not reduced");
}
if (!pool)
{
throw invalid_argument("pool is uninitialized");
}
int poly_to_eval_coeff_uint64_count = poly_to_evaluate.coeff_uint64_count();
int modulus_bit_count = modulus.significant_bit_count();
if (poly_to_evaluate.is_zero())
{
destination.set_zero();
}
if (value.is_zero())
{
destination.resize(modulus_bit_count);
modulo_uint(poly_to_evaluate.data(), poly_to_eval_coeff_uint64_count,
Modulus(modulus.data(), modulus.uint64_count(), pool),
destination.data(), pool);
return;
}
ConstPointer value_ptr = duplicate_uint_if_needed(value, modulus.uint64_count(), false, pool);
destination.resize(modulus_bit_count);
util::poly_eval_uint_mod(poly_to_evaluate.data(), poly_to_evaluate.coeff_count(), value_ptr.get(),
Modulus(modulus.data(), modulus.uint64_count(), pool), destination.data(), pool);
}
