Fix required_memory_mb

releasenotes/notes/fix_required_memory_mb-7aeafa0fe553b85a.yaml

@@ -0,0 +1,65 @@
+---
+prelude: >
+    Replace this text with content to appear at the top of the section for this
+    release. All of the prelude content is merged together and then rendered
+    separately from the items listed in other parts of the file, so the text
+    needs to be worded so that both the prelude and the other items make sense
+    when read independently. This may mean repeating some details. Not every
+    release note requires a prelude. Usually only notes describing major
+    features or adding release theme details should have a prelude.
+features:
+  - |
+    List new features here, or remove this section.  All of the list items in
+    this section are combined when the release notes are rendered, so the text
+    needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.
+issues:
+  - |
+    List known issues here, or remove this section.  All of the list items in
+    this section are combined when the release notes are rendered, so the text
+    needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.
+upgrade:
+  - |
+    List upgrade notes here, or remove this section.  All of the list items in
+    this section are combined when the release notes are rendered, so the text
+    needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.
+deprecations:
+  - |
+    List deprecations notes here, or remove this section.  All of the list
+    items in this section are combined when the release notes are rendered, so
+    the text needs to be worded so that it does not depend on any information
+    only available in another section, such as the prelude. This may mean
+    repeating some details.
+critical:
+  - |
+    Add critical notes here, or remove this section.  All of the list items in
+    this section are combined when the release notes are rendered, so the text
+    needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.
+security:
+  - |
+    Add security notes here, or remove this section.  All of the list items in
+    this section are combined when the release notes are rendered, so the text
+    needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.
+fixes:
+  - |
+    Add normal bug fixes here, or remove this section.  All of the list items
+    in this section are combined when the release notes are rendered, so the
+    text needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.
+other:
+  - |
+    Add other notes here, or remove this section.  All of the list items in
+    this section are combined when the release notes are rendered, so the text
+    needs to be worded so that it does not depend on any information only
+    available in another section, such as the prelude. This may mean repeating
+    some details.

src/simulators/density_matrix/densitymatrix_state.hpp

@@ -564,7 +564,6 @@ template <class densmat_t>
 size_t State<densmat_t>::required_memory_mb(
     uint_t num_qubits, const std::vector<Operations::Op> &ops) const {
   (void)ops; // avoid unused variable compiler warning
-  (void)ops; // avoid unused variable compiler warning
   densmat_t tmp;
   return tmp.required_memory_mb(2 * num_qubits);
 }

src/simulators/statevector/qubitvector.hpp

@@ -941,6 +941,8 @@ size_t QubitVector<data_t>::required_memory_mb(uint_t num_qubits) const {
 
   size_t unit = std::log2(sizeof(std::complex<data_t>));
   size_t shift_mb = std::max<int_t>(0, num_qubits + unit - 20);
+  if (shift_mb >= 63)
+    return SIZE_MAX;
   size_t mem_mb = 1ULL << shift_mb;
   return mem_mb;
 }

src/simulators/statevector/qubitvector_thrust.hpp

@@ -946,8 +946,9 @@ size_t QubitVectorThrust<data_t>::required_memory_mb(uint_t num_qubits) const {
 
   size_t unit = std::log2(sizeof(std::complex<data_t>));
   size_t shift_mb = std::max<int_t>(0, num_qubits + unit - 20);
+  if (shift_mb >= 63)
+    return SIZE_MAX;
   size_t mem_mb = 1ULL << shift_mb;
-
   return mem_mb;
 }
 

src/simulators/unitary/unitary_state.hpp

@@ -375,12 +375,9 @@ bool State<densmat_t>::apply_batched_op(const int_t iChunk,
 template <class unitary_matrix_t>
 size_t State<unitary_matrix_t>::required_memory_mb(
     uint_t num_qubits, const std::vector<Operations::Op> &ops) const {
-  // An n-qubit unitary as 2^2n complex doubles
-  // where each complex double is 16 bytes
   (void)ops; // avoid unused variable compiler warning
-  size_t shift_mb = std::max<int_t>(0, num_qubits + 4 - 20);
-  size_t mem_mb = 1ULL << (2 * shift_mb);
-  return mem_mb;
+  unitary_matrix_t tmp;
+  return tmp.required_memory_mb(2 * num_qubits);
 }
 
 template <class unitary_matrix_t>