Flexible and powerful tensor operations for readable and reliable code. Supports numpy, pytorch, tensorflow, and others.
In case you need convincing arguments for setting aside time to learn about einsum and einops... Tim Rocktäschel, FAIR
Writing better code with PyTorch and einops 👌 Andrej Karpathy, AI at Tesla
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, MILA (Montreal)
Tutorials are the most convenient way to see
einops in action (and right now work as a documentation)
Plain and simple:
pip install einops
einops has a minimalistic yet powerful API.
Three 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)
And two corresponding layers (
einops keeps a separate version for each framework) with the same API.
from einops.layers.chainer import Rearrange, Reduce from einops.layers.gluon import Rearrange, Reduce from einops.layers.keras import Rearrange, Reduce from einops.layers.torch import Rearrange, Reduce from einops.layers.tensorflow import Rearrange, Reduce
Layers behave similarly to operations and have the same parameters (with the exception of the first argument, which is passed during call)
layer = Rearrange(pattern, **axes_lengths) layer = Reduce(pattern, reduction, **axes_lengths) # apply created layer to a tensor / variable x = layer(x)
Example of using layers within a 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(3, 6, kernel_size=5), MaxPool2d(kernel_size=2), Conv2d(6, 16, kernel_size=5), MaxPool2d(kernel_size=2), # flattening Rearrange('b c h w -> b (c h w)'), Linear(16*5*5, 120), ReLU(), Linear(120, 10), )
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
y = x.view(x.shape, -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.
Reconsider the same example:
y = x.view(x.shape, -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 work and don't prevent mistakes as we know
y = x.view(x.shape, -1) # x: (batch, 256, 19, 19) y = rearrange(x, 'b c h w -> b (c h w)', c=256, h=19, w=19)
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?
rearrange(x, 'b c h (w w2) -> b c (h w2) w', w2=2)
Even simple functions are defined differently by different frameworks
y = x.flatten() # or flatten(x)
x's shape was
(3, 4, 5), then
y has shape ...
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 mxnet ... (etc.)
Einops works with ...
Best ways to contribute are
einopsnotation in your papers to strictly define used operations!
einops works with python 3.6 or later.