tidy up C++ layer

PennyLaneAI · Sep 9, 2024 · d1ba7d5 · d1ba7d5
1 parent bff79c2
commit d1ba7d5
Show file tree

Hide file tree

Showing 4 changed files with 6 additions and 7 deletions.
diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ### New features since last release
 
-* Add Matrix Product Operator (MPO) for all gates support to `lightning.tensor`.
+* Add Matrix Product Operator (MPO) for all gates support to `lightning.tensor`. Note current C++ implementation only works for MPO sites data provided by users. 
   [(#859)](https://github.com/PennyLaneAI/pennylane-lightning/pull/859)
 
 * Add shot measurement support to `lightning.tensor`.

diff --git a/pennylane_lightning/core/src/simulators/lightning_tensor/tncuda/MPOTNCuda.hpp b/pennylane_lightning/core/src/simulators/lightning_tensor/tncuda/MPOTNCuda.hpp
@@ -64,15 +64,14 @@ namespace Pennylane::LightningTensor::TNCuda {
  the life time of the tensor network it's applied to. Note that the gate tensor
  should be permuted to ascending order and decomposed into MPO sites before
  passing to this class.
+
  * @tparam PrecisionT Floating point type.
  */
 template <class PrecisionT> class MPOTNCuda {
   private:
     using ComplexT = std::complex<PrecisionT>;
     using CFP_t = decltype(cuUtil::getCudaType(PrecisionT{}));
 
-    // std::vector<std::size_t> wires_; // pennylane  wires convention
-
     cutensornetNetworkOperator_t MPOOperator_;
     cuDoubleComplex coeff_ =
         make_cuDoubleComplex(1.0, 0.0); // default coefficient
@@ -110,7 +109,7 @@ template <class PrecisionT> class MPOTNCuda {
      *
      * @return std::vector<void *>
      */
-    [[nodiscard]] auto getTensorsDataPtr() -> std::vector<void *> {
+    [[nodiscard]] auto getTensorsDataPtr_() -> std::vector<void *> {
         std::vector<void *> tensorsDataPtr(numMPOSites_);
         for (std::size_t i = 0; i < numMPOSites_; i++) {
             tensorsDataPtr[i] = reinterpret_cast<void *>(
@@ -253,7 +252,7 @@ template <class PrecisionT> class MPOTNCuda {
             getModeExtentsPtr_().data(),
             /* const int64_t *tensorModeStrides[] */ nullptr,
             /* const void * */
-            const_cast<const void **>(getTensorsDataPtr().data()),
+            const_cast<const void **>(getTensorsDataPtr_().data()),
             /* cutensornetBoundaryCondition_t */ boundaryCondition_,
             /* int64_t * */ &componentIdx_));
     }

diff --git a/pennylane_lightning/core/src/simulators/lightning_tensor/tncuda/MPSTNCuda.hpp b/pennylane_lightning/core/src/simulators/lightning_tensor/tncuda/MPSTNCuda.hpp
@@ -321,7 +321,7 @@ class MPSTNCuda final : public TNCudaBase<Precision, MPSTNCuda<Precision>> {
 
         // MPO configurations
         // Note that CUTENSORNET_STATE_MPO_APPLICATION_INEXACT is applied if the
-        // `cutoff` value is not set to 0 for the MPO application
+        // `cutoff` value is not set to 0 for the MPO application.
         cutensornetStateMPOApplication_t mpo_attribute =
             (cutoff == 0) ? CUTENSORNET_STATE_MPO_APPLICATION_EXACT
                           : CUTENSORNET_STATE_MPO_APPLICATION_INEXACT;

diff --git a/pennylane_lightning/lightning_tensor/_tensornet.py b/pennylane_lightning/lightning_tensor/_tensornet.py
@@ -285,7 +285,7 @@ def _apply_MPO(self, gate_matrix, wires):
 
         matrix = gate_matrix.astype(self._c_dtype)
 
-        max_mpo_bond_dim = 2 ** len(wires)  # Full decomposition
+        max_mpo_bond_dim = 2 ** len(wires)  # Exact SVD decomposition for MPO
 
         tensor_shape = [2] * len(wires) * 2