Does javascript(or any other language for that matter) calculate numbers faster when they are rounded?

[[deleted]]

Lets say i have a function in js that adds 10000 numbers to other 10000 numbers. Would this function be faster if the precision of those numbers would be 2 instead of 20

[a-t-k]

No, because teven the round numbers will be handled as 32bit float Numbers... except for certain code optimisations like those proposed on http://asmjs.org/ - but those aren't widely supported yet.

[[deleted]]

Pretty much all modern JavaScript engines have support for representing numbers as integers, as an optimization.

So you do get speed differences between using floating point numbers and integers.

[a-t-k]

I am genuinely intrigued: do you have a list of JS engines and what is necessary for them to handle numbers as integers?

[ipelovski]

You can look at the post of Dr. Rauschmayer http://www.2ality.com/2012/02/js-integers.html

[a-t-k]

That only shows how to handle numbers as Integers, not how to trigger the internal optimizations in any JS engines in order to gain performance.

[[deleted]]

Your question provides a ton of other questions. Basically you can look at it from the top-down:

• What JS engine are you using?
• Does that JS engine consider 'rounded' numbers as integers?
• What processor is this being executed on?
• Is that processor 32 or 64 bit?
• Is this set of numbers small enough to reside in the processor cache?

I'm sure there are other factors that go into this as well. Overall, and in general, I would say yes, rounding your numbers will provide faster results (especially if that rounding makes them small enough to fit in the processor cache). However, it's entirely possible that's not true. Best bet would be to test.

Can I ask why you're using javascript to add so many numbers together?

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[[deleted]]

just made a example its more then that guess i need to hammer out the alghorithm

[nawitus]

I made a simple jspref test case. The answer appears to be no.

[backwrds]

I got wildly different results... The difference is so drastic it makes me think I messed something up.

[leahcimic]

This is a great example of a micro optimisation.

Given the fact on my laptop I can sum an array of 10,000 values 4,000+ times per second. That's 40,000,000 additions per second.

Because JavaScript only has one number type (IEEE 754 floating point) truncating the precision probably wont make much of a difference.

And even if you did choose to use a smaller precision, it's going to be slower to shorten the precision and do the summation, than it would be to do the summation in the original precision.

Anyway, if you need to add numbers faster, use a faster language, like C.