def column_select_by_boolmask(column, boolmask):
"""Select by a boolean mask to a column.
Returns (selected_column, selected_positions)
"""
from cudf.dataframe.numerical import NumericalColumn
assert column.null_count == 0 # We don't properly handle the boolmask yet
boolbits = cudautils.compact_mask_bytes(boolmask.to_gpu_array())
indices = cudautils.arange(len(boolmask))
_, selinds = cudautils.copy_to_dense(indices, mask=boolbits)
_, selvals = cudautils.copy_to_dense(column.data.to_gpu_array(),
mask=boolbits)
selected_values = column.replace(data=Buffer(selvals))
selected_index = Buffer(selinds)
return selected_values, NumericalColumn(data=selected_index,
dtype=selected_index.dtype)
def _copy_to_dense_buffer(self):
data = self.data.to_gpu_array()
mask = self.mask.to_gpu_array()
nnz, mem = cudautils.copy_to_dense(data=data, mask=mask)
return Buffer(mem, size=nnz, capacity=mem.size)