As you can see, the line which has "// ALERT" tailing shows five parameters that are passed to the previously defined method which is shown to only accept three. To make matters worse, I dugg into the reference op PyOpenCL and found this: http://python-opencl.next-touch.com/tutorial.html#opencl-kernels. This code is shown in the third colored box of this part of the reference: [snip] Can someone explain to me why these approaches are so inconsistent? Which one is correct? What way is *the way to do it"?

Hello all, we're trying to get a variation on the Dijkstra algorithm to run in pyOpenCL, but we're getting a weird segmentation fault on the line where the ALERT comment is located. A print statement before and after this line indicates this position. Following is the code that initializes the arrays and stuff and loads the C code of Dijkstra (located in Dijkstra.cl): Dijkstra_cl.py: ... ctx = cl.Context([device]) queue = cl.CommandQueue(ctx, properties=cl.command_queue_properties.PROFILING_ENABLE) # Contains the resistance map table = numpy.zeros(shape=(100,100)) # Contains the remaining arguments for the Dijkstra call # [no_data_value, start_x, start_y, end_x, end_y] Dijkstra_args = numpy.ndarray((5,), buffer=numpy.array([-9999, 0, 1, 2, 3]), dtype = numpy.int32) # The map 'table' will be read from and written to by the Dijkstra-method mf = cl.mem_flags table_buff = cl.Buffer(ctx, mf.READ_WRITE | mf.USE_HOST_PTR, hostbuf = table) Dijkstra_cl_src = "" try: Dijkstra_cl_file = open("Dijkstra.cl") Dijkstra_cl_src = Dijkstra_cl_file.read() Dijkstra_cl_file.close() except IOError as error: print error prg = cl.Program(ctx, Dijkstra_cl_src).build() exec_evt = prg.Dijkstra(queue, table.shape, table_buff, Dijkstra_args) # ALERT: segfaults here exec_evt.wait() elapsed = 1e-9 * (exec_evt.profile.end - exec_evt.profile.start) print "Execution time of test: %g s" % elapsed c = numpy.empty_like(table) cl.enqueue_read_buffer(queue, table, c).wait() Dijkstra.cl: ... __kernel void Dijkstra ( __global float* resistancemap, __global const int* args ) { // Dijkstra // Remark: the parameter "resistancemap" is read from and written to, but since we've previously set the READ_WRITE flag, this should not be a problem or is it? } Can someone point us out what exactly is going wrong? I've attached both source files in case important information is missing. A second question is: is it possible to somehow debug the C-code that you build and run via print-statements or so? Regarding the second question: what about #include statements in C? The compiler just says e.g.: "file <math.h> not found" when trying to regularly including it. Thx in advance, Nick

__kernel void Dijkstra ( __global float** resistancemap, __global const int* args ) However, when trying to build this code, the following error is shown: C:\DOCUME~1\Nick\LOCALS~1\Temp\OCL123.tmp.cl(12): error: kernel must return void; pointer argument must point to addrSpace global, local, or constant __kernel void Dijkstra ( __global float** resistancemap, __global const int* args ) ^ "kernel must return void": but there is "void" in front of "Dijkstra", isn't it? "pointer argument must point to addrSpace global, local, or constant": what is causing this? the fact that there are two asterisks? "__global" is clearly present and adding "const" would be plainly wrong, since we flagged table_buff to be READ_WRITEable :-S