Alternative to np.repeat?

[harryjulian]

I tried to use .repeat to repeat a 1D array, but found it's missing from MLX at the moment.

I tried making a similar function, making use of a list for the cloning, but MLX doesn't seem to like this either.

def mlx_repeat(x, n):
    return mx.array([x for _ in range(n)])

# "ValueError: Invalid type in array initialization<class 'mlx.core.array'>."

Any ideas on the easiest / most efficient way to compute a repeat of an array with MLX at the moment?

[awni]

@harryjulian you are looking for the concatenate op. We also have a stack if that's useful.

Would be great to put a repeat as a core op. Maybe someone could contribute it!

[Bahaatbb]

@awni Hey sorry to bother you, but I would love to contribute to this can you please move me in the right direction, somewhat new to this.
are we expecting the same behavior as numpy.tile function?

[pandyaved98]

@awni I also like to work on the same. Can you please provide a bit more context so I can add the relevant code? Thanks in advance!

[awni]

Here is the function we'd like to implement: https://numpy.org/doc/stable/reference/generated/numpy.repeat.html

So the same behavior as that

[beverm2391]

Would an operation like this need to be implemented under the hood or just on top of the existing Python bindings?

[awni]

The way to do it is as a C++ op (which uses other C++ ops like reshape, concatenate, etc) with a binding to python. We don't implement functions in pure python in mlx.core

[0x1orz]

To repeat the instances of nn.Module is also in common use. Will the operator be build-in?

[awni]

To repeat the instances of nn.Module is also in common use.

@0x1orz What do you mean by that? Can you give an example?

[0x1orz]

@awni
In PyTorch, I reused a module copy like:

from copy import deepcopy
repeat = lambda module, n: [deepcopy(module) for _ in range(n)]

from torch import nn
layer = nn.Linear(2,3)
layers = repeat(layer, 2)
for layer in layers:
    layer.reset_parameters()

while in MLX,

import  mlx.nn as mlx_nn
mlx_layer = mlx_nn.Linear(2,3)
mlx_layers = repeat(mlx_layer, 2)

that raised TypeError: cannot pickle 'mlx.core.array' object.

[awni]

Ah that makes sense. Since that's such a different thing from mlx.core.repeat let's make a separate issue for it. Something like "Enable nn.Module with Python copy" (which might require making them pickle-able)

[awni]

We added repeat in #278. Will be in the next release.