Add example using new pycuda graph api.

examples/demo_graph.py

@@ -0,0 +1,66 @@
+# Sample source code from the Tutorial Introduction in the documentation.
+import pycuda.driver as cuda
+import pycuda.autoinit  # noqa
+from pycuda.compiler import SourceModule
+
+mod = SourceModule("""
+    __global__ void plus(float *a, int num)
+    {
+      int idx = threadIdx.x + threadIdx.y*4;
+      a[idx] += num;
+    }
+
+    __global__ void times(float *a, float *b)
+    {
+      int idx = threadIdx.x + threadIdx.y*4;
+      a[idx] *= b[idx];
+    }
+    """)
+func_plus = mod.get_function("plus")
+func_times = mod.get_function("times")
+
+import numpy
+a = numpy.zeros((4, 4)).astype(numpy.float32)
+a_gpu = cuda.mem_alloc_like(a)
+b = numpy.zeros((4, 4)).astype(numpy.float32)
+b_gpu = cuda.mem_alloc_like(b)
+result = numpy.zeros_like(b)
+
+# begin graph capture, pull stream_2 into it as a dependency
+#  https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#cross-stream-dependencies
+stream_1 = cuda.Stream()
+stream_2 = cuda.Stream()
+stream_1.begin_capture()
+event_init = cuda.Event()
+event_a = cuda.Event()
+event_b = cuda.Event()
+
+event_init.record(stream_1)
+stream_2.wait_for_event(event_init)
+
+cuda.memcpy_htod_async(a_gpu, a, stream_1)
+func_plus(a_gpu, numpy.int32(2), block=(4, 4, 1), stream=stream_1)
+event_a.record(stream_1)
+
+cuda.memcpy_htod_async(b_gpu, b, stream_2)
+func_plus(b_gpu, numpy.int32(3), block=(4, 4, 1), stream=stream_2)
+event_b.record(stream_2)
+
+stream_1.wait_for_event(event_a)
+stream_1.wait_for_event(event_b)
+func_times(a_gpu, b_gpu, block=(4, 4, 1), stream=stream_1)
+cuda.memcpy_dtoh_async(result, a_gpu, stream_1)
+
+graph = stream_1.end_capture()
+graph.debug_dot_print("test.dot")  # print dotfile of graph
+instance = graph.instance()
+
+# using a separate graph stream to launch, this is not strictly necessary
+stream_graph = cuda.Stream()
+instance.launch(stream_graph)
+
+print("original arrays:")
+print(a)
+print(b)
+print("(0+2)x(0+3) = 6, using a kernel graph of 3 kernels:")
+print(result)