From bb00e69b7598451129749dcb44faaebc63f08bba Mon Sep 17 00:00:00 2001
From: Jun Doi <doichan@jp.ibm.com>
Date: Tue, 21 Nov 2023 15:53:50 +0900
Subject: [PATCH] reverse ordering of read out error in sampling measure

---
 .../notes/fix_sample_measure_roerr-747b955aa2bf778c.yaml   | 7 +++++++
 src/simulators/batch_shots_executor.hpp                    | 2 +-
 src/simulators/circuit_executor.hpp                        | 2 +-
 src/simulators/multi_state_executor.hpp                    | 2 +-
 4 files changed, 10 insertions(+), 3 deletions(-)
 create mode 100644 releasenotes/notes/fix_sample_measure_roerr-747b955aa2bf778c.yaml

diff --git a/releasenotes/notes/fix_sample_measure_roerr-747b955aa2bf778c.yaml b/releasenotes/notes/fix_sample_measure_roerr-747b955aa2bf778c.yaml
new file mode 100644
index 0000000000..a36e891c3d
--- /dev/null
+++ b/releasenotes/notes/fix_sample_measure_roerr-747b955aa2bf778c.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixes order of applying read out error in sampling measure
+    in circuit executors. Ordering is reversed to fit to the older verison
+    of Aer.
+    Also fixed check of bacth execution.
diff --git a/src/simulators/batch_shots_executor.hpp b/src/simulators/batch_shots_executor.hpp
index ec98965846..3b497d9257 100644
--- a/src/simulators/batch_shots_executor.hpp
+++ b/src/simulators/batch_shots_executor.hpp
@@ -150,7 +150,7 @@ template <class state_t>
 void BatchShotsExecutor<state_t>::run_circuit_with_sampling(
     Circuit &circ, const Config &config, RngEngine &init_rng,
     ResultItr result_it) {
-  if (circ.num_bind_params == 1 || !enable_batch_multi_shots_) {
+  if (enable_batch_multi_shots_) {
     return Executor<state_t>::run_circuit_with_sampling(circ, config, init_rng,
                                                         result_it);
   }
diff --git a/src/simulators/circuit_executor.hpp b/src/simulators/circuit_executor.hpp
index 02f00224a6..aa8d70d761 100644
--- a/src/simulators/circuit_executor.hpp
+++ b/src/simulators/circuit_executor.hpp
@@ -1073,7 +1073,7 @@ void Executor<state_t>::measure_sampler(InputIterator first_meas,
   uint_t num_registers =
       (register_map.empty()) ? 0ULL : 1 + register_map.rbegin()->first;
   ClassicalRegister creg;
-  for (int_t i = 0; i < all_samples.size(); i++) {
+  for (int_t i = all_samples.size() - 1; i >= 0; i--) {
     creg.initialize(num_memory, num_registers);
 
     // process memory bit measurements
diff --git a/src/simulators/multi_state_executor.hpp b/src/simulators/multi_state_executor.hpp
index 27e533c702..be578c0da3 100644
--- a/src/simulators/multi_state_executor.hpp
+++ b/src/simulators/multi_state_executor.hpp
@@ -863,7 +863,7 @@ void MultiStateExecutor<state_t>::measure_sampler(InputIterator first_meas,
       (memory_map.empty()) ? 0ULL : 1 + memory_map.rbegin()->first;
   uint_t num_registers =
       (register_map.empty()) ? 0ULL : 1 + register_map.rbegin()->first;
-  for (int_t i = 0; i < all_samples.size(); i++) {
+  for (int_t i = all_samples.size() - 1; i >= 0; i--) {
     ClassicalRegister creg = state.creg();
 
     // process memory bit measurements