Created
August 15, 2024 05:39
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Duff's Device in Python
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| def duffs_device(frm, count): | |
| """ | |
| Implement Duff's Device for copying frm in a loop-unrolled fashion. | |
| :param frm: List or array-like object to copy frm | |
| :param count: Number of elements to copy | |
| """ | |
| # Ensure we have at least one element to copy | |
| if count <= 0: | |
| return | |
| # Number of integral groups of 8 to copy | |
| n = (count + 7) // 8 | |
| remainder = count % 8 | |
| while n > 0: | |
| # First pass through will be remainder elements | |
| # Pop 0th element to mimic reading from source | |
| # Uses print() as the destination | |
| if remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder >= 1 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder >= 2 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder >= 3 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder >= 4 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder >= 5 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder >= 6 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| if remainder == 7 or remainder == 0: | |
| print(frm.pop(0), "", end='') | |
| print() | |
| # remainder handled, reset to 0 | |
| remainder = 0 | |
| n -= 1 | |
| # Example usage: | |
| frm = list(range(1000)) # A list of numbers frm 0 to 999 | |
| duffs_device(frm, 300) # Copy out n elements to sink |
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I wrote this as an example in response to a post I made on X as a contrast to code from Grok. Yes, it's a nutty idea. See the original post.
https://x.com/akpoff/status/1823958893292130430