Added inital opencl support, extremely slow and output is not correct yet

src/distancekernel.cl

@@ -0,0 +1,35 @@
+__kernel void EuclideanDistance(__global unsigned const char *imgs,
+                                __global int *offset1_offset2_imsize_gpumem,
+                                __global float *distance)
+{
+    unsigned int sum = 0;
+
+    int img1Offset = offset1_offset2_imsize_gpumem[0];
+    int img2Offset = offset1_offset2_imsize_gpumem[1];
+    int imsize     = offset1_offset2_imsize_gpumem[2];
+
+    int lid = get_local_id(0);
+    int gid = get_global_id(0);
+    int groupSize = get_local_size(0);
+
+    __local unsigned int partial[256];
+
+    for (int i = gid; i < imsize; i += groupSize) {
+        int d = (int)imgs[img1Offset + i] - (int)imgs[img2Offset + i];
+        sum += (unsigned int)(d * d);
+    }
+
+    partial[lid] = sum;
+    barrier(CLK_LOCAL_MEM_FENCE);
+
+    for (int stride = groupSize/2; stride > 0; stride >>= 1) {
+        if (lid < stride) {
+            partial[lid] += partial[lid + stride];
+        }
+        barrier(CLK_LOCAL_MEM_FENCE);
+    }
+
+    if (lid == 0) {
+        distance[0] = (float)partial[0];
+    }
+}