What's the best way to initialize large array?

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1

For Example : I want an array of 100000 elements. But if we use [0; 100000] it will definitely give me stack overflow error because fixed arrays are allocated in stack as far as I know in rust.

So what's the best way to create an array of 100000 in rust ?

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2

vec![0; 100000] works.

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3

You can use boxed array.

let x = box [1.1f64; 10000000];

It only works in Nightly at the moment. In stable Rust you can make a vector, then unsafely cast it into a boxed array.

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[quote="anmej, post:3, topic:3458"]
In stable Rust you can make a vector, then unsafely cast it into a boxed array.
[/quote]into_boxed_slice is safe.

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5

Cool. Thanks for your help !!

6

Can you explain it why we can use vector to initialize large array?

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When you crate an (unboxed) array it will be put on the stack. The stack does not have much memory though. When you box the array or use a vector, the memory will be allocated on the heap which is much larger.

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8

You can't. Using a vec is a different approach that is often, but not always, interchangeable.

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9

Another way is

Vec::with_capacity(100_000)

This Vec has a length of 0 at first, but when it grows, it doesn't need to re-allocate.