Deftioon Posts - Answer Overflow

Deftioon

•Created by Deftioon on 1/13/2025 in #questions

An question about compile-time parameters

Hey all, So I was trying to make a Matrix struct:

#linalg.mojo
from complex import ComplexSIMD

@value
struct Matrix[rows: Int, cols: Int]:
  var data: ComplexSIMD[DType.float64, rows*cols]

  fn __init__(out self, re: Float64, im: Float64):
    self.data = ComplexSIMD[DType.float64, rows*cols](re, im)

#linalg.mojo
from complex import ComplexSIMD

@value
struct Matrix[rows: Int, cols: Int]:
  var data: ComplexSIMD[DType.float64, rows*cols]

  fn __init__(out self, re: Float64, im: Float64):
    self.data = ComplexSIMD[DType.float64, rows*cols](re, im)

When using these Matrices, its guaranteed that rows*cols is a power of two. I have another struct that uses a Matrix:

struct Foo[T: Int]:
  var state: Matrix[2**T, 1]

struct Foo[T: Int]:
  var state: Matrix[2**T, 1]

And I fill this state with a series of kronecker products of 2x2 Matrices T times, ensuring that the resulting output is definitely of shape [2**T, 1]. That looks like this:

  var filled_matrix = linalg.Matrix[2, 2](0.0, 0.0)
  for i in range(T-1):
      var new_matrix = linalg.kron(filled_matrix, IDENTITY)
      var filled_matrix = new_matrix
  self.state.replace_matrix(filled_matrix)

  var filled_matrix = linalg.Matrix[2, 2](0.0, 0.0)
  for i in range(T-1):
      var new_matrix = linalg.kron(filled_matrix, IDENTITY)
      var filled_matrix = new_matrix
  self.state.replace_matrix(filled_matrix)

Here there is an issue. I cannot put filled_matrix into self.state.

invalid call to 'replace_matrix': method argument #0 cannot be converted from 'Matrix[2, 2]' to 'Matrix[2.__pow__(T), 2.__pow__(T)]'`.

invalid call to 'replace_matrix': method argument #0 cannot be converted from 'Matrix[2, 2]' to 'Matrix[2.__pow__(T), 2.__pow__(T)]'`.

I figured this is because the compiler cannot figure out the shape of filled_matrix, even though it is guaranteed to be a Matrix[2**T, 1]. However, if I turn from compiler-time parameters to dynamic parameters, I am not sure how to create the ComplexSIMD as a struct property. Is there a way to use ComplexSIMD while also achieving this behaviour? Or will I need to use UnsafePointer instead.

2 replies

MModular

•Created by Deftioon on 1/11/2025 in #questions

Is there a way to reflect changes to a variable in the reference?

Here's a small reproducible example:

struct MyList:
    var list: List[Int]
    
    fn __init__(out self):
        self.list = List[Int]()
    
    fn __getitem__(self, index: Int) -> ref[self.list] Int:
        return self.list[index]
    
    fn append(mut self, value: Int) -> None:
        self.list.append(value)
    
    fn do_stuff(mut self, index: Int) -> None:
        self.list[index] = 1

fn main() raises -> None:
    var mylist = MyList()
    mylist.append(0)
    var q1 = mylist[0]
    print(q1)
    mylist.do_stuff(0)
    print(q1)
    print(mylist[0])

struct MyList:
    var list: List[Int]
    
    fn __init__(out self):
        self.list = List[Int]()
    
    fn __getitem__(self, index: Int) -> ref[self.list] Int:
        return self.list[index]
    
    fn append(mut self, value: Int) -> None:
        self.list.append(value)
    
    fn do_stuff(mut self, index: Int) -> None:
        self.list[index] = 1

fn main() raises -> None:
    var mylist = MyList()
    mylist.append(0)
    var q1 = mylist[0]
    print(q1)
    mylist.do_stuff(0)
    print(q1)
    print(mylist[0])

This outputs:

0
0
1

0
0
1

When I want it to output

0
1
1

0
1
1

My logic was that because q1 is a reference to mylist.list , whenever I change mylist.list, it should also be reflected in q1. But it seems q1 is copying the value instead of taking a reference? Am I misunderstanding how references work as a whole?

34 replies

Gaming

Programming