diff --git a/sw/cpp/CMakeLists.txt b/sw/cpp/CMakeLists.txt
index f1ef167..3833598 100644
--- a/sw/cpp/CMakeLists.txt
+++ b/sw/cpp/CMakeLists.txt
@@ -24,6 +24,8 @@ include_directories(${pybind11_INCLUDE_DIRS})
 
 find_package(OpenMP REQUIRED)
 
+add_compile_options(-ffast-math)
+
 pybind11_add_module(cpp_decoders src/cpp_decoders.cpp)
 target_link_libraries(cpp_decoders PRIVATE Eigen3::Eigen OpenMP::OpenMP_CXX)
 
diff --git a/sw/cpp/src/cpp_decoders.cpp b/sw/cpp/src/cpp_decoders.cpp
index bb519bf..4d3259d 100644
--- a/sw/cpp/src/cpp_decoders.cpp
+++ b/sw/cpp/src/cpp_decoders.cpp
@@ -31,7 +31,7 @@ public:
         Eigen::setNbThreads(8);
     }
 
-    const std::optional<Eigen::RowVectorXi>
+    std::pair<std::optional<Eigen::RowVectorXi>, int>
     decode(const Eigen::Ref<const Eigen::VectorXd>& y) {
         Eigen::RowVectorXd s = Eigen::RowVectorXd::Zero(mH.cols());
         Eigen::RowVectorXi x_hat;
@@ -49,11 +49,11 @@ public:
                      }).cast<int>();
 
             if (check_parity(x_hat)) {
-                return x_hat;
+                return {x_hat, i + 1};
             }
         }
 
-        return std::nullopt;
+        return {std::nullopt, mK};
     }
 
 private: