sizehint! now supports shrinking arrays #2879 #26201
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sizehint! reduces the allocated space in some cases
Top shows we are using 3.144g of memory. After using |
src/array.c
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| if (sz <= a->maxsize) { | ||
| size_t dec = a->maxsize - sz; | ||
| //if we dont save >10% of maxsize then its not worth it to shrink |
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I would make it a factor of 2, since that's the increment that we grow by.
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I disagree, going from 2 GB to 1.2 GB is a large gain. sizehint!-ing to a value shorter than the array is likely rare, and if you do, you likely want to regain the memory.
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A possible rationale for the different behavior when shrinking vs. when growing is that you strictly need to increase the storage size to push! a new element, so it makes sense to directly double the size to avoid doing it repeatedly. OTC, to call pop!, you don't strictly need to shrink the storage size: you can perfectly call resize! after a bunch of pop! calls, and it will be more efficient. So it makes sense to optimize for this case and assume the user really wants the exact requested size.
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I agree; if somebody specifically sizehint!s to a smaller size, the assumption that the array will keep growing doesn't really hold any more. We could compromise on 25% maybe?
| if (sz <= a->maxsize) { | ||
| size_t dec = a->maxsize - sz; | ||
| //if we dont save at least an eighth of maxsize then its not worth it to shrink | ||
| if (dec < a->maxsize / 8) return; |
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a->maxsize >> 3? Though the compiler may do this optimization for us.
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Putting a reference to #33974 here. cc @adrianisuru |
sizehint! reduces the allocated space in some cases