Invalid offset in buffer format string generation, when trying to use PyOpenCl with Numpy

I am porting over one of my projects from cpu to gpu and in the process I simply copied some of the code from http://documen.tician.de/pyopencl/howto.html However I keep getting a numpy error. Code:

import pyopencl as cl
import pyopencl.tools
import pyopencl.array
import numpy as np

def gpuTest():
    context = cl.create_some_context(interactive=False)
    queue = cl.CommandQueue(context)
    my_struct = np.dtype([("field1", np.int32), ("field2", np.float32)])
    my_struct, my_struct_c_decl = cl.tools.match_dtype_to_c_struct(context.devices[0], "my_struct", my_struct)
    my_struct = cl.tools.get_or_register_dtype("my_struct", my_struct)

    print(my_struct_c_decl)

    ary_host = np.empty(20, my_struct)
    ary_host["field1"].fill(217)
    ary_host["field2"].fill(1000)
    ary_host[13]["field2"] = 12

    print(ary_host)

    ary = cl.array.to_device(queue, ary_host)

    prg = cl.Program(context, my_struct_c_decl + """
    ...     __kernel void set_to_1(__global my_struct *a)
    ...     {
    ...         a[get_global_id(0)].field1 = 1;
    ...     }   
    ...     """).build()

    evt = prg.set_to_1(queue, ary.shape, None, ary.data)

    print(ary)


gpuTest()
input()

Here is the console output:

typedef struct {
  int field1;
  float field2;
} my_struct;


[(217, 1000) (217, 1000) (217, 1000) (217, 1000) (217, 1000) (217, 1000)
 (217, 1000) (217, 1000) (217, 1000) (217, 1000) (217, 1000) (217, 1000)
 (217, 1000) (217, 12) (217, 1000) (217, 1000) (217, 1000) (217, 1000)
 (217, 1000) (217, 1000)]
Traceback (most recent call last):
  File "C:\Users\\Desktop\Programming\Python Programming\Pygpu\main.py", line 36, in <module>
    gpuTest()
  File "C:\Users\\Desktop\Programming\Python Programming\Pygpu\main.py", line 22, in gpuTest
    ary = cl.array.to_device(queue, ary_host)
  File "C:\Python34\lib\site-packages\pyopencl\array.py", line 1680, in to_device
    result.set(ary, async=async)
  File "C:\Python34\lib\site-packages\pyopencl\array.py", line 670, in set
    is_blocking=not async)
  File "C:\Python34\lib\site-packages\pyopencl\__init__.py", line 1051, in enqueue_copy
    return _cl._enqueue_write_buffer(queue, dest, src, **kwargs)
RuntimeError: This should never happen: Invalid offset in buffer format string generation. Please 
report a bug to the Numpy developers.
Press any key to continue . . .

I cant seem to find anyone else who has had this kind of problem, is there something I could have done wrong when installing? Thank you in advance

[crackwitz]

https://gist.github.com/crackwitz/e13b600a1a0158cc3301918b7edf5200

if I access the mapped array fields directly, no error…

edit: the numpy docs only mention “union” once with this meaning, and that’s where this arbitrary struct definition is explained.

This form also makes it possible to specify struct dtypes with overlapping fields, functioning like the ‘union’ type in C. This usage is discouraged, however, and the union mechanism is preferred.

however, nowhere is explained what that is and how to actually do it. I’m left with doing it this way.

[seberg]

No, this is right. I think the weird thing is that the fields are in the wrong order maybe? The offset 4 is before the offset 0, is this a legal way to index fields? I.e. why does the int field have an offset of 4? it should be 0, no? and the float field should have 4?