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from __future__ import annotations
import math
def calc_chunk_sizes(
chunk_size: int | tuple[int, int] | None,
chunk_count: int | tuple[int, int] | None,
total_chunk_count: int | None,
ny: int,
nx: int,
) -> tuple[int, int]:
"""Calculate chunk sizes.
Args:
chunk_size (int or tuple(int, int), optional): Chunk size in (y, x) directions, or the same
size in both directions if only one is specified. Cannot be negative.
chunk_count (int or tuple(int, int), optional): Chunk count in (y, x) directions, or the
same count in both directions if only one is specified. If less than 1, set to 1.
total_chunk_count (int, optional): Total number of chunks. If less than 1, set to 1.
ny (int): Number of grid points in y-direction.
nx (int): Number of grid points in x-direction.
Return:
tuple(int, int): Chunk sizes (y_chunk_size, x_chunk_size).
Note:
Zero or one of ``chunk_size``, ``chunk_count`` and ``total_chunk_count`` should be
specified.
"""
if sum([chunk_size is not None, chunk_count is not None, total_chunk_count is not None]) > 1:
raise ValueError("Only one of chunk_size, chunk_count and total_chunk_count should be set")
if nx < 2 or ny < 2:
raise ValueError(f"(ny, nx) must be at least (2, 2), not ({ny}, {nx})")
if total_chunk_count is not None:
max_chunk_count = (nx-1)*(ny-1)
total_chunk_count = min(max(total_chunk_count, 1), max_chunk_count)
if total_chunk_count == 1:
chunk_size = 0
elif total_chunk_count == max_chunk_count:
chunk_size = (1, 1)
else:
factors = two_factors(total_chunk_count)
if ny > nx:
chunk_count = factors
else:
chunk_count = (factors[1], factors[0])
if chunk_count is not None:
if isinstance(chunk_count, tuple):
y_chunk_count, x_chunk_count = chunk_count
else:
y_chunk_count = x_chunk_count = chunk_count
x_chunk_count = min(max(x_chunk_count, 1), nx-1)
y_chunk_count = min(max(y_chunk_count, 1), ny-1)
chunk_size = (math.ceil((ny-1) / y_chunk_count), math.ceil((nx-1) / x_chunk_count))
if chunk_size is None:
y_chunk_size = x_chunk_size = 0
elif isinstance(chunk_size, tuple):
y_chunk_size, x_chunk_size = chunk_size
else:
y_chunk_size = x_chunk_size = chunk_size
if x_chunk_size < 0 or y_chunk_size < 0:
raise ValueError("chunk_size cannot be negative")
return y_chunk_size, x_chunk_size
def two_factors(n: int) -> tuple[int, int]:
"""Split an integer into two integer factors.
The two factors will be as close as possible to the sqrt of n, and are returned in decreasing
order. Worst case returns (n, 1).
Args:
n (int): The integer to factorize, must be positive.
Return:
tuple(int, int): The two factors of n, in decreasing order.
"""
if n < 0:
raise ValueError(f"two_factors expects positive integer not {n}")
i = math.ceil(math.sqrt(n))
while n % i != 0:
i -= 1
j = n // i
if i > j:
return i, j
else:
return j, i
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