fixed a bug with parameter selection (#893)

* fixed a bug with parameter selection * Addressed review comments --------- Co-authored-by: Yuriy Polyakov <ypolyakod@dualitytech.com> Co-authored-by: Dmitriy Suponitskiy <dsuponitskiy@dualitytech.com>
openfheorg · Oct 28, 2024 · 2592fc9 · 2592fc9
1 parent f2012fe
commit 2592fc9
Show file tree

Hide file tree

Showing 3 changed files with 13 additions and 8 deletions.
diff --git a/src/pke/lib/scheme/bgvrns/bgvrns-parametergeneration.cpp b/src/pke/lib/scheme/bgvrns/bgvrns-parametergeneration.cpp
@@ -445,7 +445,9 @@ bool ParameterGenerationBGVRNS::ParamsGenBGVRNS(std::shared_ptr<CryptoParameters
         qBound += cryptoParamsBGVRNS->EstimateMultipartyFloodingLogQ();
 
     // we add an extra bit to account for the special logic of selecting the RNS moduli in BGV
-    qBound++;
+    // ignore the case when there is only one max size modulus
+    if (qBound != auxBits)
+        qBound++;
 
     uint32_t auxTowers = 0;
     if (ksTech == HYBRID) {
@@ -482,7 +484,7 @@ bool ParameterGenerationBGVRNS::ParamsGenBGVRNS(std::shared_ptr<CryptoParameters
                     numPartQ, std::log2(moduliQ[0].ConvertToDouble()),
                     (moduliQ.size() > 1) ? std::log2(moduliQ[1].ConvertToDouble()) : 0,
                     (scalTech == FLEXIBLEAUTOEXT) ? std::log2(moduliQ[moduliQ.size() - 1].ConvertToDouble()) : 0,
-                    (scalTech == FLEXIBLEAUTOEXT) ? moduliQ.size() - 1 : moduliQ.size(), auxBits, true);
+                    (scalTech == FLEXIBLEAUTOEXT) ? moduliQ.size() - 1 : moduliQ.size(), auxBits, false);
                 newQBound += std::get<0>(hybridKSInfo);
             }
         } while (qBound < newQBound);

diff --git a/src/pke/lib/scheme/ckksrns/ckksrns-parametergeneration.cpp b/src/pke/lib/scheme/ckksrns/ckksrns-parametergeneration.cpp
@@ -78,7 +78,9 @@ bool ParameterGenerationCKKSRNS::ParamsGenCKKSRNS(std::shared_ptr<CryptoParamete
     uint32_t qBound        = firstModSize + (numPrimes - 1) * scalingModSize + extraModSize;
 
     // we add an extra bit to account for the alternating logic of selecting the RNS moduli in CKKS
-    qBound++;
+    // ignore the case when there is only one max size modulus
+    if (qBound != auxBits)
+        qBound++;
 
     // Estimate ciphertext modulus Q*P bound (in case of HYBRID P*Q)
     if (ksTech == HYBRID) {

diff --git a/src/pke/lib/schemerns/rns-cryptoparameters.cpp b/src/pke/lib/schemerns/rns-cryptoparameters.cpp
@@ -415,23 +415,24 @@ std::pair<double, uint32_t> CryptoParametersRNS::EstimateLogP(uint32_t numPartQ,
         qi[sizeQ - 1] = extraModulusSize;
 
     // Compute partitions of Q into numPartQ digits
-    double maxBits = 0;
+    uint32_t maxBits = 0;
     for (size_t j = 0; j < numPartQ; ++j) {
         size_t startTower = j * numPerPartQ;
         size_t endTower   = ((j + 1) * numPerPartQ - 1 < sizeQ) ? (j + 1) * numPerPartQ - 1 : sizeQ - 1;
 
         // sum qi elements qi[startTower] + ... + qi[endTower] inclusive. the end element should be qi.begin()+(endTower+1)
-        double bits = std::accumulate(qi.begin() + startTower, qi.begin() + (endTower + 1), 0.0);
+        uint32_t bits = static_cast<uint32_t>(std::accumulate(qi.begin() + startTower, qi.begin() + (endTower + 1), 0.0));
         if (bits > maxBits)
             maxBits = bits;
     }
 
-    // we add an extra bit to account for for the special moduli selection logic in BGV and CKKS
-    if (addOne)
+    // we add an extra bit to account for the special moduli selection logic in BGV and CKKS
+    // ignore the case when there is only one max size modulus
+    if (addOne && (maxBits != auxBits))
         maxBits++;
 
     // Select number of primes in auxiliary CRT basis
-    auto sizeP = static_cast<uint32_t>(std::ceil(maxBits / auxBits));
+    auto sizeP = static_cast<uint32_t>(std::ceil(static_cast<double>(maxBits) / auxBits));
 
     return std::make_pair(sizeP * auxBits, sizeP);
 }