OpenCL __constant oddities

Question

I am currently experimenting with OpenCL for an optimization problem, and I wrote the following kernel, which does compile correctly but it raises a CLOUT_OFRESOURCES error when executed.
++__kernel cost(__global int *out, __constant int *vertices, __constant int *edges, __global int *coloring, int k, int total) {++
++int i = getglobalid(0);++
++int color = i % k;++
++int v = i / k;++
++if (i < total) {++
++out = 0;++
++for (int j = vertices[v]; j < vertices[v + 1]; j+)+
+{+
++int w = edges[j];++
++if (color == coloring[w])++
+out++;+
+}+
+}+
+}+
I found out that the problem is declaring more than one __constant argument, i.e., the same kernel with the following signature
__kernel cost(__global int *out, __constant int *vertices, __global int *edges, __global int *coloring, int k, int total)
does compile and does not issue any error during its execution.
Is it something wrong with Apple implementation of OpenCL or is something more subtle with __constantness that I did not understand?
Thanks in advance for your help.
Luca

Answer 1

Luca DG wrote:
Is it something wrong with Apple implementation of OpenCL or is something more subtle with __constantness that I did not understand?
It appears to be a known bug in NVIDIA's compiler that Apple apparently uses - or so they say in the internet.