It's more likely you've misunderstood how slices work. From
https://golang.org/ref/spec#Slice_types:
> A slice is a descriptor for a contiguous segment of an *underlying array* and
provides access to a numbered sequence of elements from that array.
If you still believe you've found a bug we'll need the smallest reproducer
you can provide.
On Wed, May 26, 2021 at 5:27 PM John Olson <johnforestol...@gmail.com>
wrote:
> I have a recursive function that seems to be reusing memory it shouldn't.
> I'm developing in Goland 2021.1.1 with go version 1.16.2.
>
> I've written a function to generate the partitions of an integer. The
> partitions of n are all the sets of integers that add up to n, so the
> partitions of 3 are {3}, {2,1} and {1,1,1}. As n grows, the number of
> partitions grows exponentially (to be precise, as e^(n^½)). I wrote a
> recursive function, which works great up to n=7. At n=8, one of the
> partitions is {2,2,2,1}, which is obviously wrong; and since the function
> is recursive, every subsequent n is wrong, too.
>
> I just spent quite a long time stepping through the code, and I found that
> what seems to be happening is that a slice declared in my recursive
> function is being reused in two different recursions. Specifically, my
> function declares
> var temp [][]int
> to build up the list of partitions. When I compute Partitions(8), I have
> to compute Partitions(4), 5, 6 and 7. I memoize each set of partitions so I
> only have to compute them once.
>
> It all goes wrong when I'm working on Partitions(7). At this point,
> Partitions(8) has already added 6 cases, the last of which is {2,2,2,2}.
> This is stored in temp[5], the temp corresponding to n=8, of course. Then I
> compute Partitions(7), which should create a new temp [][]int; I'll call
> this temp//7. temp[6]//7 gets {2,2,2,1}, and at that point temp[5]//8
> changes from {2,2,2,2} to {2,2,2,1}. The addresses of temp[6]//7 and
> temp[5]//8 are different, but the addresses of the *elements* of these
> slices are the same.
>
> This has to be wrong.
>
> I suspect a bug in go, but I suppose it's possible there's a bug in
> goland. I'm running on macOS 11.3.1, just in case that's relevant.
>
> I'm happy to share the source code if anyone is interested.
>
> Thanks,
>
> J
>
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>
--
Kurtis Rader
Caretaker of the exceptional canines Junior and Hank
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