From b86a78968d9d85db8d9f87fe2bc5d119192c9bed Mon Sep 17 00:00:00 2001
From: vvilpas <vvilpas@gmail.com>
Date: Wed, 7 Apr 2021 17:29:28 +0200
Subject: [PATCH] Disable GPU methods if no device available

---
 src/controllers/aer_controller.hpp |  6 ++++++
 src/controllers/controller.hpp     | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/controllers/aer_controller.hpp b/src/controllers/aer_controller.hpp
index 35ff6e4085..a01f8a162a 100755
--- a/src/controllers/aer_controller.hpp
+++ b/src/controllers/aer_controller.hpp
@@ -502,6 +502,12 @@ void Controller::set_config(const json_t &config) {
         throw std::runtime_error(
             "Simulation device \"GPU\" is not supported on this system");
 #else
+        int nDev;
+        if (cudaGetDeviceCount(&nDev) != cudaSuccess) {
+            cudaGetLastError();
+            throw std::runtime_error("No CUDA device available!");
+        }
+
         sim_device_ = Device::GPU;
 #endif
       }
diff --git a/src/controllers/controller.hpp b/src/controllers/controller.hpp
index d5e4da14c0..7ba9157903 100755
--- a/src/controllers/controller.hpp
+++ b/src/controllers/controller.hpp
@@ -300,6 +300,20 @@ class Controller {
 //-------------------------------------------------------------------------
 
 void Controller::set_config(const json_t &config) {
+#ifdef AER_THRUST_CUDA
+  {
+    std::string method;
+    if (JSON::get_value(method, "method", config)) {
+      if(method.find("gpu") != std::string::npos){
+        int nDev;
+        if (cudaGetDeviceCount(&nDev) != cudaSuccess) {
+          cudaGetLastError();
+          throw std::runtime_error("No CUDA device available!");
+        }
+      }
+    }
+  }
+#endif
 
   // Load validation threshold
   JSON::get_value(validation_threshold_, "validation_threshold", config);