Modular•7mo ago

Easier way to sum a list of integers

Hello there, I'm trying to learn Mojo by creating some small simple programs and comparing them to Python to learn key differences. I've joined an example of the last function I wrote in my code. In this specific case, get_unbiased_run returns an integer value and the goal of this function is to sum the value of all runs. In Python, one would do a simple one liner by summing all elements of a generator. I don't know what the equivalent would be in mojo and believe this code can be optimised. I've noticed the existence of Buffers and the "sum" function from the algorithm module but not sure how I could make it work here. Any help is welcomed ! Thanks in advance 🙂

11 Replies

Grandimam•7mo ago

I do not see aggregate functions in the doc. However, you can do something like this:

fn main():
    var c: Int = 0
    fn add(a: Int, /) capturing:
        c += a
    map[add](5)

fn main():
    var c: Int = 0
    fn add(a: Int, /) capturing:
        c += a
    map[add](5)

bunny•7mo ago

map[add](5) ... does this require some kind of import or something? Sorry for noob Q -- while I'm an aspiring Mojician, I still consider myself a Mojician's Assistant.

Jake Brooks•7mo ago

Since the map function isn't part of the builtin module, you'll need to explicitly import it: from algorithm import map

ModularBot•7mo ago

Congrats @Jake Brooks, you just advanced to level 1!

bunny•7mo ago

ty! For any other potential readers: https://docs.modular.com/mojo/stdlib/algorithm/functional Ty again, @Jake Brooks . 😊

benny•7mo ago

@seboll13 is your goal speed or simplify ease of writing/using code? If it is speed then youll want to look into Parameters, unroll, and SIMD instructions (like reduce_add), if its just ease of use then the above answers are fantastic :)

bunny•7mo ago

I have to admit, my brain needs a rewire. I imagine others might feel the same. Generally when I'm programming in Python/JS/shell(don't-judge-me)/other-interp-languages, I think approach problems in a somewhat "hacky" way. But as soon as I'm doing Go/Rust/C/other-compiled-languages, I suddenly approach them from a more optimized vantage. Mojo is really messing with my brain. In a good way.

ModularBot•7mo ago

Congrats @bunny, you just advanced to level 3!

seboll13OP•7mo ago

I’d say a bit of the two but mostly speed. I’m trying to optimise as best I can in order to see what’s the fastest execution time I can get. But thanks for your input 🙂

benny•7mo ago

if you send the full code I can help, but likely SIMD will be the way to go

seboll13OP•7mo ago

I’ll understand how it works then and get back to you if needed:)

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Easier way to sum a list of integers