added stereo_multi_gpu sample, cosmetic changes in multi_gpu sample

samples/gpu/stereo_multi.cpp

@@ -0,0 +1,183 @@
+/* This sample demonstrates working on one piece of data using two GPUs.
+   It splits input into two parts and processes them separately on different
+   GPUs. */
+
+// Disable some warnings which are caused with CUDA headers
+#pragma warning(disable: 4201 4408 4100)
+
+#include <iostream>
+#include <cvconfig.h>
+#include <opencv2/core/core.hpp>
+#include <opencv2/highgui/highgui.hpp>
+#include <opencv2/gpu/gpu.hpp>
+
+#if !defined(HAVE_CUDA) || !defined(HAVE_TBB)
+
+int main()
+{
+#if !defined(HAVE_CUDA)
+    cout << "CUDA support is required (CMake key 'WITH_CUDA' must be true).\n";
+#endif
+
+#if !defined(HAVE_TBB)
+    cout << "TBB support is required (CMake key 'WITH_TBB' must be true).\n";
+#endif
+
+    return 0;
+}
+
+#else
+
+#include <cuda.h>
+#include <cuda_runtime.h>
+#include "opencv2/core/internal.hpp" // For TBB wrappers
+
+using namespace std;
+using namespace cv;
+using namespace cv::gpu;
+
+struct Worker { void operator()(int device_id) const; };
+void destroyContexts();
+
+#define safeCall(code) if (code != CUDA_SUCCESS) { \
+    cout << "CUDA driver API error: code " << code \
+        << ", file " << __FILE__ << ", line " << __LINE__ << endl; \
+    destroyContexts(); \
+    exit(-1); \
+}
+
+// Each GPU is associated with its own context
+CUcontext contexts[2];
+
+void inline contextOn(int id) 
+{
+    safeCall(cuCtxPushCurrent(contexts[id]));
+}
+
+void inline contextOff() 
+{
+    CUcontext prev_context;
+    safeCall(cuCtxPopCurrent(&prev_context));
+}
+
+GpuMat d_left[2];
+GpuMat d_right[2];
+StereoBM_GPU* bm[2];
+GpuMat d_result[2];
+Mat result;
+
+int main(int argc, char** argv)
+{
+    if (argc < 3)
+    {
+        cout << "Usage: stereo_multi_gpu <left_image> <right_image>\n";
+        return -1;
+    }
+
+    int num_devices = getCudaEnabledDeviceCount();
+
+    if (num_devices < 2)
+    {
+        cout << "Two or more GPUs are required\n";
+        return -1;
+    }
+
+    for (int i = 0; i < num_devices; ++i)
+    {
+        if (!DeviceInfo(i).isCompatible())
+        {
+            cout << "GPU module isn't built for GPU #" << i << " (" << DeviceInfo(i).name() << ")";
+            return -1;
+        }
+    }
+
+    // Load input data
+    Mat left = imread(argv[1], CV_LOAD_IMAGE_GRAYSCALE);
+    Mat right = imread(argv[2], CV_LOAD_IMAGE_GRAYSCALE);
+    if (left.empty())
+    {
+        cout << "Cannot open '" << argv[1] << "'\n";
+        return -1;
+    }
+    if (right.empty())
+    {
+        cout << "Cannot open '" << argv[2] << "'\n";
+        return -1;
+    }
+
+    safeCall(cuInit(0));
+
+    // Create context for the first GPU
+    CUdevice device;
+    safeCall(cuDeviceGet(&device, 0));
+    safeCall(cuCtxCreate(&contexts[0], 0, device));
+    contextOff();
+
+    // Create context for the second GPU
+    safeCall(cuDeviceGet(&device, 1));
+    safeCall(cuCtxCreate(&contexts[1], 0, device));
+    contextOff();
+
+    // Split source images for processing on the first GPU
+    contextOn(0);
+    d_left[0].upload(left.rowRange(0, left.rows / 2));
+    d_right[0].upload(right.rowRange(0, right.rows / 2));
+    bm[0] = new StereoBM_GPU();
+    contextOff();
+
+    // Split source images for processing on the second GPU
+    contextOn(1);
+    d_left[1].upload(left.rowRange(left.rows / 2, left.rows));
+    d_right[1].upload(right.rowRange(right.rows / 2, right.rows));
+    bm[1] = new StereoBM_GPU();
+    contextOff();
+
+    // Execute calculation in two threads using two GPUs
+    int devices[] = {0, 1};
+    parallel_do(devices, devices + 2, Worker());
+
+    // Release the first GPU resources
+    contextOn(0);
+    imshow("GPU #0 result", Mat(d_result[0]));
+    d_left[0].release();
+    d_right[0].release();
+    d_result[0].release();
+    delete bm[0];
+    contextOff();
+
+    // Release the second GPU resources
+    contextOn(1);
+    imshow("GPU #1 result", Mat(d_result[1]));
+    d_left[1].release();
+    d_right[1].release();
+    d_result[1].release();
+    delete bm[1];
+    contextOff();
+
+    waitKey();
+    destroyContexts();
+    return 0;
+}
+
+
+void Worker::operator()(int device_id) const
+{
+    contextOn(device_id);
+
+    bm[device_id]->operator()(d_left[device_id], d_right[device_id],
+                              d_result[device_id]);
+
+    cout << "GPU #" << device_id << " (" << DeviceInfo().name()
+        << "): finished\n";
+
+    contextOff();
+}
+
+
+void destroyContexts()
+{
+    safeCall(cuCtxDestroy(contexts[0]));
+    safeCall(cuCtxDestroy(contexts[1]));
+}
+
+#endif