wp.struct: from numpy and back
jc211 opened this issue · comments
Hi,
I am wondering how to move wp.arrays of type my_struct back and forth between numpy and cuda. At the moment, only one direction seems to work:
@wp.struct
class foo:
temp: int
a_d = wp.zeros((10,), dtype=my_struct) # works
a = a_d.numpy() # works
a_d = wp.from_numpy(a, dtype=my_struct) # does not workThe error is:
warp/warp/types.py", line 1325, in _init_from_data
raise RuntimeError(f"Error while trying to construct Warp array from a sequence of Warp structs: {e}")
RuntimeError: Error while trying to construct Warp array from a sequence of Warp structs: 'numpy.void' object has no attribute '__ctype__
Am I doing something wrong?
It could be done like below:
@wp.struct
class foo:
temp: int
a_d = wp.zeros((10,), dtype=my_struct)
a = a_d.to("cpu")
a_numpy = np.asarray(a, dtype=my_struct.numpy_dtype())
a_numpy["temp"] = 3Although it would be cleaner if from_numpy() worked on structs
Hi @jc211, I agree that wp.from_numpy() should handle this gracefully. We'll get that fixed shortly. In the meantime, please consider using this helper function:
def from_numpy_structs(a, dtype, device=None):
# wrap numpy array as a host array using the pointer
a_h = wp.array(ptr=a.ctypes.data, dtype=dtype, shape=a.shape, device="cpu", copy=False, owner=False)
# resolve the device
device = wp.get_device(device)
if device.is_cpu:
# keep a back reference to prevent the numpy array from getting deallocated
a_h._ref = a
return a_h
else:
# copy to device
return a_h.to(device)
Your code would change like this:
a_d = wp.zeros((10,), dtype=my_struct) # works
a = a_d.numpy() # works
a_d = from_numpy_structs(a, my_struct) # workaround
