Fix cudaq::slice_vector synthesis bug and add test

lib/Optimizer/Transforms/QuakeSynthesizer.cpp

@@ -166,15 +166,14 @@ synthesizeVectorArgument(OpBuilder &builder, ModuleOp module, unsigned &counter,
 
   auto replaceLoads = [&](cudaq::cc::ComputePtrOp elePtrOp,
                           Value newVal) -> LogicalResult {
+    bool allLoadUsers = true;
     for (auto *u : elePtrOp->getUsers()) {
-      if (auto loadOp = dyn_cast<cudaq::cc::LoadOp>(u)) {
+      if (auto loadOp = dyn_cast<cudaq::cc::LoadOp>(u))
         loadOp.replaceAllUsesWith(newVal);
-        continue;
-      }
-      return elePtrOp.emitError(
-          "Unknown gep/load configuration for synthesis.");
+      else
+        allLoadUsers = false;
     }
-    return success();
+    return success(allLoadUsers);
   };
 
   // Iterate over the users of this stdvec argument.
@@ -221,9 +220,7 @@ synthesizeVectorArgument(OpBuilder &builder, ModuleOp module, unsigned &counter,
               Value memArr = getArrayInMemory();
               builder.setInsertionPoint(elePtrOp);
               Value newComputedPtr = builder.create<cudaq::cc::ComputePtrOp>(
-                  argLoc, ptrEleTy, memArr,
-                  SmallVector<cudaq::cc::ComputePtrArg>{
-                      0, elePtrOp.getDynamicIndices()[0]});
+                  argLoc, ptrEleTy, memArr, elePtrOp.getDynamicIndices()[0]);
               elePtrOp.replaceAllUsesWith(newComputedPtr);
             }
             continue;

targettests/Remote-Sim/observe_h2.cpp

@@ -0,0 +1,128 @@
+/*******************************************************************************
+ * Copyright (c) 2022 - 2024 NVIDIA Corporation & Affiliates.                  *
+ * All rights reserved.                                                        *
+ *                                                                             *
+ * This source code and the accompanying materials are made available under    *
+ * the terms of the Apache License 2.0 which accompanies this distribution.    *
+ ******************************************************************************/
+
+// REQUIRES: remote-sim
+
+// clang-format off
+// RUN: nvq++ %cpp_std --target remote-mqpu --remote-mqpu-auto-launch 1 %s -o %t && %t
+// RUN: nvq++ %cpp_std --enable-mlir --target remote-mqpu --remote-mqpu-auto-launch 1 %s -o %t && %t
+// clang-format on
+
+// Note: this is similar to the vqe_h2.cpp example file, but it uses
+// cudaq::observe instead of cudaq::vqe in order to exercise quake-synth on
+// vector parameters with complicated usage patterns (like cudaq::slice_vector).
+
+#include <cudaq.h>
+#include <cudaq/algorithm.h>
+#include <cudaq/builder.h>
+#include <cudaq/gradients.h>
+#include <cudaq/optimizers.h>
+
+// Here we build up a CUDA-Q kernel with N layers and each
+// layer containing an arrangement of random SO(4) rotations. The algorithm
+// leverages the CUDA-Q VQE support to compute the ground state of the
+// Hydrogen atom.
+
+// The SO4 random entangler written as a CUDA-Q kernel free function
+// since this is a pure-device quantum kernel
+__qpu__ void so4(cudaq::qubit &q, cudaq::qubit &r,
+                 const std::vector<double> &thetas) {
+  ry(thetas[0], q);
+  ry(thetas[1], r);
+
+  h(r);
+  cx(q, r);
+  h(r);
+
+  ry(thetas[2], q);
+  ry(thetas[3], r);
+
+  h(r);
+  cx(q, r);
+  h(r);
+
+  ry(thetas[4], q);
+  ry(thetas[5], r);
+
+  h(r);
+  cx(q, r);
+  h(r);
+}
+
+// The SO4 fabric CUDA-Q kernel. Keeps track of simple
+// arithmetic class members controlling the number of qubits and
+// entangling layers.
+struct so4_fabric {
+  void operator()(std::vector<double> params, int n_qubits,
+                  int n_layers) __qpu__ {
+    cudaq::qvector q(n_qubits);
+
+    x(q[0]);
+    x(q[2]);
+
+    const int block_size = 2;
+    int counter = 0;
+    for (int i = 0; i < n_layers; i++) {
+      // first layer of so4 blocks (even)
+      for (int k = 0; k < n_qubits; k += 2) {
+        auto subq = q.slice(k, block_size);
+        auto so4_params = cudaq::slice_vector(params, counter, 6);
+        so4(subq[0], subq[1], so4_params);
+        counter += 6;
+      }
+
+      // second layer of so4 blocks (odd)
+      for (int k = 1; k + block_size < n_qubits; k += 2) {
+        auto subq = q.slice(k, block_size);
+        auto so4_params = cudaq::slice_vector(params, counter, 6);
+        so4(subq[0], subq[1], so4_params);
+        counter += 6;
+      }
+    }
+  }
+};
+
+int main() {
+  // Read in the spin op from file
+  std::vector<double> h2_data{0, 0, 0, 0, -0.10647701149499994, 0.0,
+                              1, 1, 1, 1, 0.0454063328691,      0.0,
+                              1, 1, 3, 3, 0.0454063328691,      0.0,
+                              3, 3, 1, 1, 0.0454063328691,      0.0,
+                              3, 3, 3, 3, 0.0454063328691,      0.0,
+                              2, 0, 0, 0, 0.170280101353,       0.0,
+                              2, 2, 0, 0, 0.120200490713,       0.0,
+                              2, 0, 2, 0, 0.168335986252,       0.0,
+                              2, 0, 0, 2, 0.165606823582,       0.0,
+                              0, 2, 0, 0, -0.22004130022499996, 0.0,
+                              0, 2, 2, 0, 0.165606823582,       0.0,
+                              0, 2, 0, 2, 0.174072892497,       0.0,
+                              0, 0, 2, 0, 0.17028010135300004,  0.0,
+                              0, 0, 2, 2, 0.120200490713,       0.0,
+                              0, 0, 0, 2, -0.22004130022499999, 0.0,
+                              15};
+  cudaq::spin_op H(h2_data, /*nQubits*/ 4);
+
+  // For 8 qubits, 36 parameters per layer
+  int n_layers = 2, n_qubits = H.num_qubits(), block_size = 2, p_counter = 0;
+  int n_blocks_per_layer = 2 * (n_qubits / block_size) - 1;
+  int n_params = n_layers * 6 * n_blocks_per_layer;
+  printf("%d qubit Hamiltonian -> %d parameters\n", n_qubits, n_params);
+
+  // Define the initial parameters and ansatz. For this test, make a linear ramp
+  // from -1 to 1.
+  std::vector<double> init_params(n_params);
+  for (int i = 0; i < n_params; i++)
+    init_params[i] = -1 + i * (2.0 / n_params);
+
+  so4_fabric ansatz;
+
+  auto energy =
+      cudaq::observe(ansatz, H, init_params, n_qubits, n_layers).expectation();
+  printf("energy %f\n", energy);
+  assert(std::abs(energy - -0.320848) < 1e-3);
+}