minor changes in multi_gpu sample

samples/gpu/multi.cpp

@@ -0,0 +1,122 @@
+// 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/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 cuSafeCall(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];
+
+
+int main()
+{
+    if (getCudaEnabledDeviceCount() < 2)
+    {
+        cout << "Two or more GPUs are required\n";
+        return -1;
+    }
+
+    cuSafeCall(cuInit(0));
+
+    // Create context for the first GPU
+    CUdevice device;
+    cuSafeCall(cuDeviceGet(&device, 0));
+    cuSafeCall(cuCtxCreate(&contexts[0], 0, device));
+
+    CUcontext prev_context;
+    cuSafeCall(cuCtxPopCurrent(&prev_context));
+
+    // Create context for the second GPU
+    cuSafeCall(cuDeviceGet(&device, 1));
+    cuSafeCall(cuCtxCreate(&contexts[1], 0, device));
+
+    cuSafeCall(cuCtxPopCurrent(&prev_context));
+
+    // Execute calculation in two threads using two GPUs
+    int devices[] = {0, 1};
+    parallel_do(devices, devices + 2, Worker());
+
+    destroyContexts();
+    return 0;
+}
+
+
+void Worker::operator()(int device_id) const
+{
+    // Set proper context
+    cuSafeCall(cuCtxPushCurrent(contexts[device_id]));
+
+    Mat src(1000, 1000, CV_32F);
+    Mat dst;
+
+    RNG rng(0);
+    rng.fill(src, RNG::UNIFORM, 0, 1);
+
+    // CPU works
+    transpose(src, dst);
+
+    GpuMat d_src(src);
+    GpuMat d_dst;
+
+    // GPU works
+    transpose(d_src, d_dst);
+
+    // Check results
+    bool passed = norm(dst - Mat(d_dst), NORM_INF) < 1e-3;
+    cout << "GPU #" << device_id << ": "<< (passed ? "passed" : "FAILED") << endl;
+
+    // Deallocate data here, otherwise deallocation will be performed
+    // after context is extracted from the stack
+    d_src.release();
+    d_dst.release();
+
+    CUcontext prev_context;
+    cuSafeCall(cuCtxPopCurrent(&prev_context));
+}
+
+
+void destroyContexts()
+{
+    cuSafeCall(cuCtxDestroy(contexts[0]));
+    cuSafeCall(cuCtxDestroy(contexts[1]));
+}
+
+#endif