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