add auto-configuration of threads for qasm simulator

contrib/standalone/qasm_simulator.cpp

@@ -22,12 +22,15 @@
 
 enum class CmdArguments {
   SHOW_VERSION,
+  INPUT_CONFIG,
   INPUT_DATA
 };
 
 inline CmdArguments parse_cmd_options(const std::string& argv){
   if(argv == "-v" || argv == "--version"){
-       return CmdArguments::SHOW_VERSION;
+    return CmdArguments::SHOW_VERSION;
+  } else if (argv == "-c" || argv == "--config"){
+    return CmdArguments::INPUT_CONFIG;
   }
   return CmdArguments::INPUT_DATA;
 }
@@ -54,16 +57,18 @@ inline void usage(const std::string& command, std::ostream &out){
   show_version();
   std::cerr << "\n";
   std::cerr << "Usage: \n";
-  std::cerr << command << " [-v] <file>\n";
-  std::cerr << "    -v    Show version\n";
-  std::cerr << "    file : qobj file\n";
+  std::cerr << command << " [-v] [-c <config>] <file>\n";
+  std::cerr << "    -v          : Show version\n";
+  std::cerr << "    -c <config> : Configuration file\n";;
+  std::cerr << "    file        : qobj file\n";
 }
 
 int main(int argc, char **argv) {
 
   std::ostream &out = std::cout; // output stream
   int indent = 4;
   json_t qobj;
+  json_t config;
 
   if(argc == 1){
     usage(std::string(argv[0]), out);
@@ -76,9 +81,22 @@ int main(int argc, char **argv) {
       case CmdArguments::SHOW_VERSION:
         show_version();
         return 0;
+      case CmdArguments::INPUT_CONFIG:
+        if (++pos == static_cast<unsigned int>(argc)) {
+          failed("Invalid config (no file is specified.)", out, indent);
+          return 1;
+        }
+        try {
+          config = JSON::load(std::string(argv[pos]));
+        }catch(std::exception &e){
+          std::string msg = "Invalid config (" +  std::string(e.what()) + ")";
+          failed(msg, out, indent);
+          return 1;
+        }
+        break;
       case CmdArguments::INPUT_DATA:
         try {
-          qobj = JSON::load(std::string(argv[1]));
+          qobj = JSON::load(std::string(argv[pos]));
           pos = argc; //Exit from the loop
         }catch(std::exception &e){
           std::string msg = "Invalid input (" +  std::string(e.what()) + ")";
@@ -94,8 +112,14 @@ int main(int argc, char **argv) {
 
     // Initialize simulator
     AER::Simulator::QasmController sim;
+
     // Check for config
-    sim.set_config(qobj["config"]);
+    json_t config_all = qobj["config"];
+    if (!config.empty())
+      config_all.update(config.begin(), config.end());
+
+    sim.set_config(config_all);
+
     out << sim.execute(qobj).dump(4) << std::endl;
 
     return 0;

qiskit/providers/aer/backends/aerbackend.py

@@ -115,9 +115,9 @@ def _format_qobj_str(self, qobj, backend_options, noise_model):
         if backend_options is not None:
             for key, val in backend_options.items():
                 config[key] = val
-        if "available_memory" not in config:
-            available_mb = int(local_hardware_info()['memory'] * 1024)
-            config['available_memory'] = available_mb
+        if "max_memory_mb" not in config:
+            max_memory_mb = int(local_hardware_info()['memory'] * 1024 / 2)
+            config['max_memory_mb'] = max_memory_mb
         # Add noise model
         if noise_model is not None:
             config["noise_model"] = noise_model

qiskit/providers/aer/backends/qasm_simulator.py

@@ -43,7 +43,7 @@ class QasmSimulator(AerBackend):
             available memory, uses the statevector method. Otherwise, uses
             the ch method (Default: "automatic").
 
-        * "available_memory" (int): Set the amount of memory (in MB)
+        * "max_memory_mb" (int): Set the amount of memory (in MB)
         the simulator has access to (Default: Maximum available)
 
         * "initial_statevector" (vector_like): Sets a custom initial
@@ -71,6 +71,12 @@ class QasmSimulator(AerBackend):
             Note that this cannot be enabled at the same time as parallel
             experiment execution (Default: 1).
 
+        * "max_statevector_memory_mb" (int): Sets the maximum size of memory
+            to store a state vector. If a state vector needs more, an error
+            is thrown. In general, a state vector of n-qubits uses 2^n complex
+            values (16 Bytes). If set to 0, the maximum will be automatically
+            set to the system memory size (Default: 0).
+
         * "statevector_parallel_threshold" (int): Sets the threshold that
             "n_qubits" must be greater than to enable OpenMP
             parallelization for matrix multiplication during execution of