Update mutable list reallocation#4103
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d-torrance wants to merge 5 commits intoMacaulay2:developmentfrom
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Update mutable list reallocation#4103d-torrance wants to merge 5 commits intoMacaulay2:developmentfrom
d-torrance wants to merge 5 commits intoMacaulay2:developmentfrom
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d-torrance
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The only time we ever needed a List instead of an Expr when creating a List object directly was in copy, and we only needed this in a few places, so we just use the list() constructor and copy the sequence instead. Also simplify sethash -- no need to pass is_mutable separately since that information is kept in the list. Also remove unused "newlist" function
This is to keep track of the amount that we have allocated for mutable lists.
This fixes an old issue from bugs/dan, so we remove it
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antonleykin
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Feb 5, 2026
| hash:hash_t, | ||
| Mutable:bool | ||
| Mutable:bool, | ||
| capacity:int -- amount of allocated memory (for mutable lists) |
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Does it add one word to every list (mutable or not)?
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Yes, it does. It's redundant for immutable lists since this will always agree with the length of the underlying sequence.
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Currently, when we add an element to a mutable list, we reallocate exactly enough memory to fit the new element. So doing something like
for i to n - 1 do x##x = iconstructs n brand new mutable lists.Instead, we double the length of the underlying sequence if needed. (And also halve it if it gets small from repeated calls to
remove.)So each list
xnow has two lengths:length(x.v)-- the "visible" length at top levelx.capacity-- the actual length allocated for the underlying sequenceEdit: Originally, I had these swapped, but that broke pretty much everything, since so much code depends on
x.vhaving exactly the same elements asx.For immutable lists, these two numbers should always be the same.
I changed some pretty low-level stuff, so chances are there are bugs... Draft for now
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Closes: #659