Add vector class enter/exit data demo

gpu-openmp/demos/vector.cpp

@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+class Vector {
+    public:
+    Vector(int n) : len(n) {
+        v = new double[len];
+        #pragma omp target enter data map(alloc:v[0:len])
+    }
+    ~Vector() {
+        #pragma omp target exit data map(delete:v[0:len])
+        delete[] v;
+    }
+    double *v;
+    int len;
+};
+
+int main(void)
+{
+    int N=1000;
+    int i;
+    Vector vec = Vector(N);
+    double *v = vec.v;
+
+    for (i=0; i<N; i++) {
+        vec.v[i] = 0.5;
+    }
+#pragma omp target update to(vec.v[0:N])
+
+#pragma omp target teams
+#pragma omp distribute parallel for
+    for (i=0; i<N; i++) {
+        v[i] = v[i] * v[i];
+    }
+
+#pragma omp target update from(vec.v[0:N])
+    printf("%f %f %f\n", vec.v[0], vec.v[1], vec.v[2]);
+
+    return 0;
+}