Replace PyCuda with CuPy

Replaces PyCuda with CuPy

Advantages of CuPy:

• AMD support
• probably higher maintained due to NVIDIA support
• SciPy compatible.

Fixes #70 (closed) Fixes #69 (closed)

pystencils/__init__.py

@@ -43,10 +43,9 @@ del get_versions
 
 # setting the default GPU to the one with maximal memory. GPU_DEVICE is safe to overwrite for different needs
 try:
-  import cupy
-  if cupy.cuda.runtime.getDeviceCount() > 0:
-    GPU_DEVICE = sorted(range(cupy.cuda.runtime.getDeviceCount()),
-                        key=lambda i: cupy.cuda.Device(i).mem_info[1], reverse=True)[0]
+    import cupy
+    if cupy.cuda.runtime.getDeviceCount() > 0:
+        GPU_DEVICE = sorted(range(cupy.cuda.runtime.getDeviceCount()),
+                            key=lambda i: cupy.cuda.Device(i).mem_info[1], reverse=True)[0]
 except ImportError:
-  pass
-
+    pass