experimental/sources/: einops-0.8.0 metadata and description

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A new flavour of deep learning operations

author Alex Rogozhnikov
  • Intended Audience :: Science/Research
  • License :: OSI Approved :: MIT License
  • Programming Language :: Python :: 3
description_content_type text/markdown
keywords deep learning,einops,machine learning,neural networks,scientific computations,tensor manipulation
license MIT
  • Homepage, https://github.com/arogozhnikov/einops
requires_python >=3.8
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Flexible and powerful tensor operations for readable and reliable code.
Supports numpy, pytorch, tensorflow, jax, and others.

Recent updates:

Previous updates - flax and oneflow backend added - torch.jit.script is supported for pytorch layers - powerful EinMix added to einops. [Einmix tutorial notebook](https://github.com/arogozhnikov/einops/blob/master/docs/3-einmix-layer.ipynb)


In case you need convincing arguments for setting aside time to learn about einsum and einops... Tim Rocktäschel

Writing better code with PyTorch and einops 👌 Andrej Karpathy

Slowly but surely, einops is seeping in to every nook and cranny of my code. If you find yourself shuffling around bazillion dimensional tensors, this might change your life Nasim Rahaman

More testimonials



Plain and simple:

pip install einops


Tutorials are the most convenient way to see einops in action

Kapil Sachdeva recorded a small intro to einops.


einops has a minimalistic yet powerful API.

Three core operations provided (einops tutorial shows those cover stacking, reshape, transposition, squeeze/unsqueeze, repeat, tile, concatenate, view and numerous reductions)

from einops import rearrange, reduce, repeat
# rearrange elements according to the pattern
output_tensor = rearrange(input_tensor, 't b c -> b c t')
# combine rearrangement and reduction
output_tensor = reduce(input_tensor, 'b c (h h2) (w w2) -> b h w c', 'mean', h2=2, w2=2)
# copy along a new axis
output_tensor = repeat(input_tensor, 'h w -> h w c', c=3)

Later additions to the family are pack and unpack functions (better than stack/split/concatenate):

from einops import pack, unpack
# pack and unpack allow reversibly 'packing' multiple tensors into one.
# Packed tensors may be of different dimensionality:
packed,  ps = pack([class_token_bc, image_tokens_bhwc, text_tokens_btc], 'b * c')
class_emb_bc, image_emb_bhwc, text_emb_btc = unpack(transformer(packed), ps, 'b * c')

Finally, einops provides einsum with a support of multi-lettered names:

from einops import einsum, pack, unpack
# einsum is like ... einsum, generic and flexible dot-product 
# but 1) axes can be multi-lettered  2) pattern goes last 3) works with multiple frameworks
C = einsum(A, B, 'b t1 head c, b t2 head c -> b head t1 t2')


EinMix is a generic linear layer, perfect for MLP Mixers and similar architectures.


Einops provides layers (einops keeps a separate version for each framework) that reflect corresponding functions

from einops.layers.torch      import Rearrange, Reduce
from einops.layers.tensorflow import Rearrange, Reduce
from einops.layers.flax       import Rearrange, Reduce
from einops.layers.paddle     import Rearrange, Reduce
from einops.layers.chainer    import Rearrange, Reduce
Example of using layers within a pytorch model Example given for pytorch, but code in other frameworks is almost identical
from torch.nn import Sequential, Conv2d, MaxPool2d, Linear, ReLU
from einops.layers.torch import Rearrange

model = Sequential(
    Conv2d(6, 16, kernel_size=5),
    # flattening without need to write forward
    Rearrange('b c h w -> b (c h w)'),  
    Linear(16*5*5, 120), 
    Linear(120, 10), 

No more flatten needed!

Additionally, torch users will benefit from layers as those are script-able and compile-able.


einops stands for Einstein-Inspired Notation for operations (though "Einstein operations" is more attractive and easier to remember).

Notation was loosely inspired by Einstein summation (in particular by numpy.einsum operation).

Why use einops notation?!

Semantic information (being verbose in expectations)

y = x.view(x.shape[0], -1)
y = rearrange(x, 'b c h w -> b (c h w)')

While these two lines are doing the same job in some context, the second one provides information about the input and output. In other words, einops focuses on interface: what is the input and output, not how the output is computed.

The next operation looks similar:

y = rearrange(x, 'time c h w -> time (c h w)')

but it gives the reader a hint: this is not an independent batch of images we are processing, but rather a sequence (video).

Semantic information makes the code easier to read and maintain.

Convenient checks

Reconsider the same example:

y = x.view(x.shape[0], -1) # x: (batch, 256, 19, 19)
y = rearrange(x, 'b c h w -> b (c h w)')

The second line checks that the input has four dimensions, but you can also specify particular dimensions. That's opposed to just writing comments about shapes since comments don't prevent mistakes, not tested, and without code review tend to be outdated

y = x.view(x.shape[0], -1) # x: (batch, 256, 19, 19)
y = rearrange(x, 'b c h w -> b (c h w)', c=256, h=19, w=19)

Result is strictly determined

Below we have at least two ways to define the depth-to-space operation

# depth-to-space
rearrange(x, 'b c (h h2) (w w2) -> b (c h2 w2) h w', h2=2, w2=2)
rearrange(x, 'b c (h h2) (w w2) -> b (h2 w2 c) h w', h2=2, w2=2)

There are at least four more ways to do it. Which one is used by the framework?

These details are ignored, since usually it makes no difference, but it can make a big difference (e.g. if you use grouped convolutions in the next stage), and you'd like to specify this in your code.


reduce(x, 'b c (x dx) -> b c x', 'max', dx=2)
reduce(x, 'b c (x dx) (y dy) -> b c x y', 'max', dx=2, dy=3)
reduce(x, 'b c (x dx) (y dy) (z dz) -> b c x y z', 'max', dx=2, dy=3, dz=4)

These examples demonstrated that we don't use separate operations for 1d/2d/3d pooling, those are all defined in a uniform way.

Space-to-depth and depth-to space are defined in many frameworks but how about width-to-height? Here you go:

rearrange(x, 'b c h (w w2) -> b c (h w2) w', w2=2)

Framework independent behavior

Even simple functions are defined differently by different frameworks

y = x.flatten() # or flatten(x)

Suppose x's shape was (3, 4, 5), then y has shape ...

einops works the same way in all frameworks.

Independence of framework terminology

Example: tile vs repeat causes lots of confusion. To copy image along width:

np.tile(image, (1, 2))    # in numpy
image.repeat(1, 2)        # pytorch's repeat ~ numpy's tile

With einops you don't need to decipher which axis was repeated:

repeat(image, 'h w -> h (tile w)', tile=2)  # in numpy
repeat(image, 'h w -> h (tile w)', tile=2)  # in pytorch
repeat(image, 'h w -> h (tile w)', tile=2)  # in tf
repeat(image, 'h w -> h (tile w)', tile=2)  # in jax
repeat(image, 'h w -> h (tile w)', tile=2)  # in cupy
... (etc.)

Testimonials provide users' perspective on the same question.

Supported frameworks

Einops works with ...

Additionally, starting from einops 0.7.0 einops can be used with any framework that supports Python array API standard

Citing einops

Please use the following bibtex record

    title={Einops: Clear and Reliable Tensor Manipulations with Einstein-like Notation},
    author={Alex Rogozhnikov},
    booktitle={International Conference on Learning Representations},

Supported python versions

einops works with python 3.8 or later.