How to construct `LayoutTensor` from `RuntimeLayout`

GPU Programming
1

Hi!

I’m trying to better understand how RuntimeLayout works. To avoid boilerplate, I am trying to write a function that just converts a buffer into a row major LayoutTensor. I have this code:

from gpu.host import DeviceContext, DeviceBuffer, HostBuffer
from layout import Layout, LayoutTensor, RuntimeLayout, RuntimeTuple
from layout.int_tuple import UNKNOWN_VALUE

alias fp16 = DType.float16

fn row_major_of_buffer[dtype: DType](mut buffer: DeviceBuffer, M: Int, N: Int):
    alias layout = Layout.row_major(UNKNOWN_VALUE, UNKNOWN_VALUE)
    var dyn = RuntimeLayout[layout](
        RuntimeTuple[layout.shape](M, N),
        RuntimeTuple[layout.stride](N, 1)
    )
    return LayoutTensor[dtype, layout](buffer, dyn)

def main():
    ctx = DeviceContext()
    M = 128
    K = 32

    A_buffer = ctx.enqueue_create_buffer[fp16](M * K)
    var device_A = row_major_of_buffer[fp16](A_buffer, M, K)

but it breaks with several errors around not finding a proper constructor for LayoutTensor.

Looking through LayoutTensor | Modular,

I see several options:

  • span, runtime_layout
  • ptr, runtime_layout

I have tried converting my buffer to both, but also not had any success. I feel like I am probably doing something fundamentally wrong, but I’m not sure what. Any thoughts?