Fixed GetBootstrapDepth (openfheorg#626)

* updated GetBootstrapDepth * Update simple-ckks-bootstrapping.cpp --------- Co-authored-by: Yuriy Polyakov <ypolyakod@dualitytech.com>
gong-cr · Dec 22, 2023 · fea4dec · fea4dec
1 parent ec7a78d
commit fea4dec
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Showing 3 changed files with 18 additions and 13 deletions.
diff --git a/src/pke/examples/iterative-ckks-bootstrapping.cpp b/src/pke/examples/iterative-ckks-bootstrapping.cpp
@@ -184,6 +184,7 @@ void IterativeBootstrapExample() {
 
     // Output the precision of bootstrapping after two iterations. It should be approximately double the original precision.
     std::cout << "Bootstrapping precision after 2 iterations: " << precisionMultipleIterations << std::endl;
-    std::cout << "Number of levels remaining after 2 bootstrappings: " << depth - ciphertextTwoIterations->GetLevel()
+    std::cout << "Number of levels remaining after 2 bootstrappings: "
+              << depth - ciphertextTwoIterations->GetLevel() - (ciphertextTwoIterations->GetNoiseScaleDeg() - 1)
               << std::endl;
 }
diff --git a/src/pke/examples/simple-ckks-bootstrapping.cpp b/src/pke/examples/simple-ckks-bootstrapping.cpp
@@ -99,6 +99,9 @@ void SimpleBootstrapExample() {
     */
     std::vector<uint32_t> levelBudget = {4, 4};
 
+    // Note that the actual number of levels avalailable after bootstrapping before next bootstrapping 
+    // will be levelsAvailableAfterBootstrap - 1 because an additional level
+    // is used for scaling the ciphertext before next bootstrapping (in 64-bit CKKS bootstrapping)
     uint32_t levelsAvailableAfterBootstrap = 10;
     usint depth = levelsAvailableAfterBootstrap + FHECKKSRNS::GetBootstrapDepth(levelBudget, secretKeyDist);
     parameters.SetMultiplicativeDepth(depth);
@@ -139,7 +142,8 @@ void SimpleBootstrapExample() {
     // for HE computation.
     auto ciphertextAfter = cryptoContext->EvalBootstrap(ciph);
 
-    std::cout << "Number of levels remaining after bootstrapping: " << depth - ciphertextAfter->GetLevel() << std::endl
+    std::cout << "Number of levels remaining after bootstrapping: "
+              << depth - ciphertextAfter->GetLevel() - (ciphertextAfter->GetNoiseScaleDeg() - 1) << std::endl
               << std::endl;
 
     Plaintext result;

diff --git a/src/pke/lib/scheme/ckksrns/ckksrns-fhe.cpp b/src/pke/lib/scheme/ckksrns/ckksrns-fhe.cpp
@@ -167,7 +167,7 @@ void FHECKKSRNS::EvalBootstrapSetup(const CryptoContextImpl<DCRTPoly>& cc, std::
         double scaleDec  = 1 / pre;
 
         uint32_t approxModDepth = GetModDepthInternal(cryptoParams->GetSecretKeyDist());
-        uint32_t depthBT        = approxModDepth + 1 + precom->m_paramsEnc[CKKS_BOOT_PARAMS::LEVEL_BUDGET] +
+        uint32_t depthBT        = approxModDepth + precom->m_paramsEnc[CKKS_BOOT_PARAMS::LEVEL_BUDGET] +
                            precom->m_paramsDec[CKKS_BOOT_PARAMS::LEVEL_BUDGET];
 
         // compute # of levels to remain when encoding the coefficients
@@ -295,7 +295,7 @@ void FHECKKSRNS::EvalBootstrapPrecompute(const CryptoContextImpl<DCRTPoly>& cc,
     double scaleDec  = 1 / pre;
 
     uint32_t approxModDepth = GetModDepthInternal(cryptoParams->GetSecretKeyDist());
-    uint32_t depthBT        = approxModDepth + 1 + precom->m_paramsEnc[CKKS_BOOT_PARAMS::LEVEL_BUDGET] +
+    uint32_t depthBT        = approxModDepth + precom->m_paramsEnc[CKKS_BOOT_PARAMS::LEVEL_BUDGET] +
                        precom->m_paramsDec[CKKS_BOOT_PARAMS::LEVEL_BUDGET];
 
     // compute # of levels to remain when encoding the coefficients
@@ -2107,10 +2107,10 @@ uint32_t FHECKKSRNS::GetBootstrapDepthInternal(uint32_t approxModDepth, const st
 
 uint32_t FHECKKSRNS::GetModDepthInternal(SecretKeyDist secretKeyDist) {
     if (secretKeyDist == UNIFORM_TERNARY) {
-        return GetMultiplicativeDepthByCoeffVector(g_coefficientsUniform, true) + R_UNIFORM;
+        return GetMultiplicativeDepthByCoeffVector(g_coefficientsUniform, false) + R_UNIFORM;
     }
     else {
-        return GetMultiplicativeDepthByCoeffVector(g_coefficientsSparse, true) + R_SPARSE;
+        return GetMultiplicativeDepthByCoeffVector(g_coefficientsSparse, false) + R_SPARSE;
     }
 }
 
@@ -2355,8 +2355,8 @@ Plaintext FHECKKSRNS::MakeAuxPlaintext(const CryptoContextImpl<DCRTPoly>& cc, co
     if (logc < 0) {
         OPENFHE_THROW(math_error, "Too small scaling factor");
     }
-    int32_t logValid    = (logc <= MAX_BITS_IN_WORD) ? logc : MAX_BITS_IN_WORD;
-    int32_t logApprox   = logc - logValid;
+    int32_t logValid = (logc <= MAX_BITS_IN_WORD) ? logc : MAX_BITS_IN_WORD;
+    int32_t logApprox = logc - logValid;
     double approxFactor = pow(2, logApprox);
 
     std::vector<int64_t> temp(2 * slots);
@@ -2387,11 +2387,11 @@ Plaintext FHECKKSRNS::MakeAuxPlaintext(const CryptoContextImpl<DCRTPoly>& cc, co
                 double imagVal = prodFactor.imag();
 
                 if (realVal > realMax) {
-                    realMax    = realVal;
+                    realMax = realVal;
                     realMaxIdx = idx;
                 }
                 if (imagVal > imagMax) {
-                    imagMax    = imagVal;
+                    imagMax = imagVal;
                     imagMaxIdx = idx;
                 }
             }
@@ -2414,11 +2414,11 @@ Plaintext FHECKKSRNS::MakeAuxPlaintext(const CryptoContextImpl<DCRTPoly>& cc, co
         int64_t re = std::llround(dre);
         int64_t im = std::llround(dim);
 
-        temp[i]         = (re < 0) ? Max64BitValue() + re : re;
+        temp[i] = (re < 0) ? Max64BitValue() + re : re;
         temp[i + slots] = (im < 0) ? Max64BitValue() + im : im;
     }
 
-    const std::shared_ptr<ILDCRTParams<BigInteger>> bigParams        = plainElement.GetParams();
+    const std::shared_ptr<ILDCRTParams<BigInteger>> bigParams = plainElement.GetParams();
     const std::vector<std::shared_ptr<ILNativeParams>>& nativeParams = bigParams->GetParams();
 
     for (size_t i = 0; i < nativeParams.size(); i++) {
@@ -2454,7 +2454,7 @@ Plaintext FHECKKSRNS::MakeAuxPlaintext(const CryptoContextImpl<DCRTPoly>& cc, co
     // Scale back up by the approxFactor to get the correct encoding.
     if (logApprox > 0) {
         int32_t logStep = (logApprox <= MAX_LOG_STEP) ? logApprox : MAX_LOG_STEP;
-        auto intStep    = DCRTPoly::Integer(uint64_t(1) << logStep);
+        auto intStep = DCRTPoly::Integer(uint64_t(1) << logStep);
         std::vector<DCRTPoly::Integer> crtApprox(numTowers, intStep);
         logApprox -= logStep;