Sequence of matrix-vector multiplications

[JanW92]

Hello,
I am implementing a matrix-vector multiplication as following:
`
Ring ring;
SecretKey sk(ring);
Scheme scheme(sk, ring);
long logq = 800; ///< Ciphertext Modulus. Should be smaller than logQ in "src/Params.h" : 800
long logp = 40; ///Scaling factor.

//Should be smaller than logN in "src/Params.h" : 16 => Max Slots = 65536
long logn = 7; // -> 128
long n = 1<< logn;

for (int j = 0; j < circuitDepth; j ++)
{
	std::cout << "Multiplication " << j << std::endl;

	//Perform matrix-vector multiplication
	scheme.mult(c_multiplicationResult,c_matrix[0],c_fieldVec);

	//new cM: logq = logq², logp = logp - logq -> rescale, so that it can be added with c_addIdentity
	scheme.reScaleByAndEqual(c_multiplicationResult, logp);

	//No multiplication was performed on c_addIdentity, therefore logq still has the initial value. In order to add it with cM the
            //logp must match as well.
	scheme.modDownByAndEqual(c_addIdentity, logp);

	//At the end of the process c_fieldVec will get the value from c_result, which has the same logp and logq as cM now.
	//For the next multiplication process they have to match.
	scheme.modDownByAndEqual(c_matrix[0],logp);
	scheme.add(c_result, c_multiplicationResult, c_addIdentity);

	scheme.leftRotateFastAndEqual(c_fieldVec, r);

	for(int i = 1; i< n; i++)
	{
		scheme.mult(c_multiplicationResult,c_matrix[i],c_fieldVec);
		scheme.reScaleByAndEqual(c_multiplicationResult, logp);
		scheme.modDownByAndEqual(c_matrix[i],logp);
		scheme.addAndEqual(c_result, c_multiplicationResult);

		scheme.leftRotateFastAndEqual(c_fieldVec, r);

	}
   }

`
The first multiplication gives me the expected result. But the second result consists of values with 10^187, which I have seen occasionally when the parameter were not correct.
Even though the logp and logq of c_matrix[0] and c_fieldVec matches and I have plenty of bits left (740), the second multiplication does not bring the expected result.
Does someone have an idea what I am doing wrong? Any hint would be much appreciated.

[swanhong]

Hi, I've tested your code, but no such error has occurred. In my experiment, I used random inputs for c_matrix, c_fieldVec, etc, so it would be better if you share your exact code or your input data.