Modular•6mo ago

Create a SIMD[DType.address] from a DTypePointer[T]

It would seem like DTypePointer[T].address_of(SIMD[T) would be correct, but this returns a DTypePointer aswell, which has type T, not DType.address. A bitcast seems incorrect as this would directly cast the numeric value into a pointer location, which is wrong, and I do not feel that loading the data as an address is the correct answer either. Hoping to use gather and scatter on SIMD vectors from a DTypePointer if possible.

11 Replies

ModularBot•6mo ago

Congrats @benny, you just advanced to level 8!

Maxim•6mo ago

I had the same question. 🙂

benny•6mo ago

any luck? i’m still stuck

Maxim•6mo ago

Same I think since 24.1.0 you can write int(p) and get the int representation of the pointer address, so I thought maybe I can wrap it in SIMD[DType.address,1] but this also doesn’t work. I have a feeling it’s something which was introduced early, but now needs reworking so until it’s done, nobody wants to talk about it 😀.

benny•6mo ago

@Jack Clayton any insight on this? still havent found a solution

Jack Clayton•6mo ago

Hi @benny is this what you're looking for:

fn main():
    var x = Int64(42)
    var p =Pointer[Scalar[DType.int64]].address_of(x)
    print(int(p))

fn main():
    var x = Int64(42)
    var p =Pointer[Scalar[DType.int64]].address_of(x)
    print(int(p))

Or are you trying to fill a SIMD vec with addresses?

benny•6mo ago

that is the issue yes for potentially use with gather / scatter (that’s the required input) i figured once stdlib is open sourced their may be some use of what i’m trying to do in there I can look for, but until then I got nothing

Jack Clayton•6mo ago

Ok haven't seen that, asking the team

adakkak•6mo ago

You should be able to do SIMD[DType.address](int(my_pointer)) E.g.

fn main():
    var x = Int64(42)
    var p = DTypePointer.address_of(x)
    print(int(p))
    print(SIMD[DType.address, 4](int(p)).type)

fn main():
    var x = Int64(42)
    var p = DTypePointer.address_of(x)
    print(int(p))
    print(SIMD[DType.address, 4](int(p)).type)

sadly print on DType.address is broken right now. Will fix

benny•6mo ago

perfect! thank you so much :)

alain•6mo ago

Finally, we can try to actually use gather/scatter based on this. There is an open change request to make that way less clunky but Mojo team considers it 'just semantic sugar'. Kind request for the first successful example code using gather and scatter to be shared amongst mojicans !

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Programming

Create a SIMD[DType.address] from a DTypePointer[T]