Tweaks.

Signed-off-by: Eric Schweitz <[email protected]>

Author: schweitzpgi

runtime/common/SimulationState.h

@@ -73,26 +73,17 @@ class SimulationState {
   /// and extract the data pointer and size.
   template <typename ScalarType = double>
   auto getSizeAndPtr(const state_data &data) {
-    auto type = data.index();
-    std::tuple<std::size_t, void *> sizeAndPtr;
-    if (type ==
-        cudaq::detail::variant_index<cudaq::state_data,
-                                     std::vector<std::complex<double>>>())
-      sizeAndPtr = getSizeAndPtrFromVec<double, ScalarType>(data);
-    else if (type ==
-             cudaq::detail::variant_index<cudaq::state_data,
-                                          std::vector<std::complex<float>>>())
-      sizeAndPtr = getSizeAndPtrFromVec<float, ScalarType>(data);
-    else if (type == cudaq::detail::variant_index<
-                         cudaq::state_data,
-                         std::pair<std::complex<double> *, std::size_t>>())
-      sizeAndPtr = getSizeAndPtrFromPair<double, ScalarType>(data);
-    else if (type == cudaq::detail::variant_index<
-                         cudaq::state_data,
-                         std::pair<std::complex<float> *, std::size_t>>())
-      sizeAndPtr = getSizeAndPtrFromPair<float, ScalarType>(data);
-    else if (type == cudaq::detail::variant_index<cudaq::state_data,
-                                                  complex_matrix>()) {
+    if (std::holds_alternative<std::vector<std::complex<double>>>(data))
+      return getSizeAndPtrFromVec<double, ScalarType>(data);
+    if (std::holds_alternative<std::vector<std::complex<float>>>(data))
+      return getSizeAndPtrFromVec<float, ScalarType>(data);
+    if (std::holds_alternative<std::pair<std::complex<double> *, std::size_t>>(
+            data))
+      return getSizeAndPtrFromPair<double, ScalarType>(data);
+    if (std::holds_alternative<std::pair<std::complex<float> *, std::size_t>>(
+            data))
+      return getSizeAndPtrFromPair<float, ScalarType>(data);
+    if (std::holds_alternative<complex_matrix>(data)) {
       // Complex matrix is double precision only
       if constexpr (!std::is_same_v<double, ScalarType>)
         throw std::runtime_error("[sim-state] invalid data precision.");
@@ -108,10 +99,8 @@ class SimulationState {
           cMat.size(),
           reinterpret_cast<void *>(const_cast<complex_matrix &>(cMat).get_data(
               complex_matrix::order::row_major)));
-    } else
-      throw std::runtime_error("unsupported data type for state vector.");
-
-    return sizeAndPtr;
+    }
+    throw std::runtime_error("unsupported data type for state vector.");
   }
 
   /// @brief Subclass-specific creator method for