diff --git a/dlib/dnn/cuda_dlib.cu b/dlib/dnn/cuda_dlib.cu
index 8b4824b11..fb4fa4d13 100644
--- a/dlib/dnn/cuda_dlib.cu
+++ b/dlib/dnn/cuda_dlib.cu
@@ -27,6 +27,14 @@ namespace dlib
             return dev;
         }
 
+        int get_num_devices (
+        )
+        {
+            int num_devices;
+            CHECK_CUDA(cudaGetDeviceCount(&num_devices));
+            return num_devices;
+        }
+
     // -----------------------------------------------------------------------------------
 
         __global__ void _cuda_multiply1(float* d, const float* s1, const float* s2, size_t n)
diff --git a/dlib/dnn/cuda_dlib.h b/dlib/dnn/cuda_dlib.h
index 1a8bfdc28..ab81d44e1 100644
--- a/dlib/dnn/cuda_dlib.h
+++ b/dlib/dnn/cuda_dlib.h
@@ -22,6 +22,9 @@ namespace dlib
         int get_device (
         );
 
+        int get_num_devices (
+        );
+
     // -----------------------------------------------------------------------------------
 
         void multiply (
@@ -165,6 +168,9 @@ namespace dlib
         inline int get_device (
         ){ return 0; }
 
+        int get_num_devices (
+        ) { return 1; }
+
 #endif // DLIB_USE_CUDA
 
     }