how to handle very large array?

[bauss]

On Wednesday, 9 February 2022 at 10:03:21 UTC, MichaelBi wrote:
> day6 of the advent of code 2021 needs to handle an array of 
> 10^12 length, or even bigger... plus change elements and append 
> elements. normal implementation such as length, appender and 
> ref element etc, seems cannot handle that big array? is there 
> any alternative data structure or algorithm can handle such 
> large array properly? thanks.

Use a memorymapped file that holds the array values, in theory it 
can be infinite then.

Since an array has a known size for each entry then you can treat 
the file as an array.

Let's say you have an array of ints.

For a memorymapped file you obviously only have bytes to work 
with, so each entry will be 4 bytes, since a 32 bit integer (int) 
is 4 bytes.

So to read something at a specific index you simply do N x I 
where N is the size of the type and I is the index you want to 
read at.

Otherwise the size of an array cannot exceed the RAM you have, if 
your system can't use diskspace as RAM of course.