Silk.NET•3y ago

casting a Vector3<int> to Vector3 (float) for equality should be fine, right

MaxineOP•10/20/23, 10:38 PM

since it's just a memory comparison

Aqua•10/20/23, 10:38 PM

eehhhh
i really don't see how this is any faster than just doing a logical compare

AAqua eehhhh i really don't see how this is any faster than just doing a logical compa...

MaxineOP•10/20/23, 10:38 PM

for AsVector128

MMaxine casting a Vector3<int> to Vector3 (float) for equality should be fine, right

TechPizza•10/20/23, 10:39 PM

throws out all float rules out of window i see

Perksey•10/20/23, 10:39 PM

doesn't Span have a really efficient equality implementation already?

Aqua•10/20/23, 10:39 PM

intrinsics can often be slower if you're just using them for one singular operation

MMaxine casting a Vector3<int> to Vector3 (float) for equality should be fine, right

Perksey•10/20/23, 10:39 PM

// USE AN EPSILON DAMNIT!

// USE AN EPSILON DAMNIT!

PPerksey doesn't Span have a really efficient equality implementation already?

MaxineOP•10/20/23, 10:39 PM

so i should just create a Span<T> for this and other and equals that?

MaxineOP•10/20/23, 10:39 PM

that would both be generalizable and fast

MaxineOP•10/20/23, 10:39 PM

possibly

MaxineOP•10/20/23, 10:39 PM

if the JIT created the right instructions

Perksey•10/20/23, 10:40 PM

sure but you're trading correctness for performance

MaxineOP•10/20/23, 10:40 PM

what do you mean correctness, Vector3 Equals was never meant to use an epsilon

Perksey•10/20/23, 10:40 PM

it is conceivably possible that the same effective float value has differing bits

MaxineOP•10/20/23, 10:41 PM

yep i just figured out why this wouldn't work

MaxineOP•10/20/23, 10:41 PM

things like -0 and +0

MaxineOP•10/20/23, 10:41 PM

NaN equality

PPerksey sure but you're trading correctness for performance

Aqua•10/20/23, 10:41 PM

i'm not even sure it would be more performant

Aqua•10/20/23, 10:41 PM

or if it is, its negligable

Perksey•10/20/23, 10:41 PM

it'd be more performant for gigantic structs

Aqua•10/20/23, 10:41 PM

you're replacing instructions with other instructions

Aqua•10/20/23, 10:41 PM

true, but not for a small one like vectors

Aqua•10/20/23, 10:41 PM

matrix probably

Perksey•10/20/23, 10:41 PM

oh yeah

Aqua•10/20/23, 10:41 PM

but not vectors

Perksey•10/20/23, 10:41 PM

like seriously please just use specialised impls

AAqua i'm not even sure it would be more performant

MaxineOP•10/20/23, 10:42 PM

i jsut adapted this

Aqua•10/20/23, 10:42 PM

maybe there is something i am missing ¯\_(ツ)_/¯

MaxineOP•10/20/23, 10:42 PM

should i throw this all out and jus compare XYZ? that's fine with me

Aqua•10/20/23, 10:42 PM

i've done the experiments with SIMD and vectors

Aqua•10/20/23, 10:43 PM

and in my tests its far slower than to just do the operations directly

Aqua•10/20/23, 10:43 PM

because of the amount of extra bulk that goes along with it

Aqua•10/20/23, 10:43 PM

simd comes into its own when you do an operation multiple times, just once its often worse for perf

Aqua•10/20/23, 10:43 PM

which is why matrix benefits from simd

Aqua•10/20/23, 10:43 PM

if i'm wrong please correct me, this is just from the results of my own experiments

TechPizza•10/20/23, 10:44 PM

i would say that using SIMD for Vector4 is perfectly fine

TechPizza•10/20/23, 10:44 PM

Vector2 and Vector3 is way too painful due to not being the size of a Vector128

Perksey•10/20/23, 10:46 PM

if (Vector128.IsHardwareAccelerated && typeof(T) == typeof(float))
{
    return Unsafe.BitCast<Vector3<T>, Vector3>(this).AsVector128().Equals(Unsafe.BitCast<Vector3<T>, Vector3>(other).AsVector128());
}

if (Vector128.IsHardwareAccelerated && typeof(T) == typeof(float))
{
    return Unsafe.BitCast<Vector3<T>, Vector3>(this).AsVector128().Equals(Unsafe.BitCast<Vector3<T>, Vector3>(other).AsVector128());
}

MaxineOP•10/20/23, 10:46 PM

is that a .net 8 method

MaxineOP•10/20/23, 10:47 PM

i like it

PPerksey ```cs if (Vector128.IsHardwareAccelerated && typeof(T) == typeof(float)) { r...

Aqua•10/20/23, 10:48 PM

again, just replacing instructions with other instructions
sure,

BitCast

BitCast

may be fast, but you're introducing a comparison, a function call, etc.

MaxineOP•10/20/23, 10:48 PM

those should be inlined

MaxineOP•10/20/23, 10:48 PM

typeof(T) == typeof(Y) gets inlined

Aqua•10/20/23, 10:48 PM

hmmm yes fair point

MaxineOP•10/20/23, 10:48 PM

IsHardwareAcceleration gets eliminated

Aqua•10/20/23, 10:48 PM

i know that

MaxineOP•10/20/23, 10:49 PM

the most expensive thing here is the new Vector4

Perksey•10/20/23, 10:49 PM

yeah all of that will be inlined and understood by the JIT

MaxineOP•10/20/23, 10:49 PM

and the SIMD itself

if (Vector128.IsHardwareAccelerated && typeof(T) == typeof(float)) { return Unsafe.BitCast<Vector3<T>, Vector3>(this).AsVector128().Equals(Unsafe.BitCast<Vector3<T>, Vector3>(other).AsVector128()); }

casting a Vector3<int> to Vector3 (float) for equality should be fine, right

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