Today I am pleased to present you two new Open Source projects:

  • torchlayers
  • torchlambda

torchlayers introduction

Project was created with the following goals in mind:

  • Help newcomers join the field (by providing shape and dimension inference for all torch.nn.Module objects provided by PyTorch)
  • Increased developers/researchers productivity (more default values common in community, aforementioned shape inference)
  • Easier experimentation with current State Of The Art architectures (building blocks known from PolyNet, Squeeze-And-Excitation or Efficient-Net

Please see whole project description (examples, installation etc.) after torchlambda introduction.

torchlambda introduction

Project was created with the following goals in mind:

  • Easy and lightweight PyTorch model deployment using AWS Lambda
  • Single dependency, no S3 needed hence less infrastructure to manage (PyTorch torchscript compiled module can be provided as AWS Lambda Layer, see example deployment after torchlambda full description)
  • Easy yet close to bare metal when optimization needed using C++ and PyTorch C++ API
  • Easy way to customize builder itself (libtorch and AWS C++ SDK can be customized during torchlambda deploy command)
  • Easily installable (just run pip install torchlambda).

Please see whole project description (examples, installation etc.) after torchlayer full description.

torchlayers full description

Version Docs Tests Coverage Style PyPI Python PyTorch Docker
Version Documentation Tests Coverage codebeat PyPI Python PyTorch Docker

torchlayers is a library based on PyTorch providing automatic shape and dimensionality inference of torch.nn layers + additional building blocks featured in current SOTA architectures (e.g. Efficient-Net).

Above requires no user intervention (except single call to similarly to the one seen in Keras.

Main functionalities:

  • Shape inference for most of torch.nn module (convolutional, recurrent, transformer, attention and linear layers)
  • Dimensionality inference (e.g. torchlayers.Conv working as torch.nn.Conv1d/2d/3d based on input shape)
  • Shape inference of custom modules (see examples section)
  • Additional Keras-like layers (e.g. torchlayers.Reshape or torchlayers.StandardNormalNoise)
  • Additional SOTA layers mostly from ImageNet competitions (e.g. PolyNet, Squeeze-And-Excitation, StochasticDepth)
  • Useful defaults ("same" padding and default kernel_size=3 for Conv, dropout rates etc.)
  • Zero overhead and torchscript support


For full functionality please check torchlayers documentation. Below examples should introduce all necessary concepts you should know.

Simple convolutional image and text classifier

  • We will use single "model" for both tasks. Firstly let's define it using torch.nn and torchlayers:
import torch
import torchlayers

# torch.nn and torchlayers can be mixed easily
model = torch.nn.Sequential(
    torchlayers.Conv(64),  # specify ONLY out_channels
    torch.nn.ReLU(),  # use torch.nn wherever you wish
    torchlayers.BatchNorm(),  # BatchNormNd inferred from input
    torchlayers.Conv(128),  # Default kernel_size equal to 3
    torchlayers.Conv(256, kernel_size=11),  # "same" padding as default
    torchlayers.GlobalMaxPool(),  # Known from Keras
    torchlayers.Linear(10),  # Output for 10 classes


Above would give you model's summary like this (notice question marks for not yet inferred values):

  (0): Conv(in_channels=?, out_channels=64, kernel_size=3, stride=1, padding=same, dilation=1, groups=1, bias=True, padding_mode=zeros)
  (1): ReLU()
  (2): BatchNorm(num_features=?, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
  (3): Conv(in_channels=?, out_channels=128, kernel_size=3, stride=1, padding=same, dilation=1, groups=1, bias=True, padding_mode=zeros)
  (4): ReLU()
  (5): Conv(in_channels=?, out_channels=256, kernel_size=11, stride=1, padding=same, dilation=1, groups=1, bias=True, padding_mode=zeros)
  (6): GlobalMaxPool()
  (7): Linear(in_features=?, out_features=10, bias=True)
  • Now you can build/instantiate your model with example input (in this case MNIST-like):
mnist_model =, torch.randn(1, 3, 28, 28))
  • Or if it's text classification you are after, same model could be built with different input shape (e.g. for text classification using 300 dimensional pretrained embedding):
# [batch, embedding, timesteps], first dimension > 1 for BatchNorm1d to work
text_model =, torch.randn(2, 300, 1))
  • Finally, you can print both models after instantiation, provided below side by-side for readability (notice different dimenstionality, e.g. Conv2d vs Conv1d after
                # MNIST CLASSIFIER                TEXT CLASSIFIER

                Sequential(                       Sequential(
                  (0): Conv1d(300, 64)              (0): Conv2d(3, 64)
                  (1): ReLU()                       (1): ReLU()
                  (2): BatchNorm1d(64)              (2): BatchNorm2d(64)
                  (3): Conv1d(64, 128)              (3): Conv2d(64, 128)
                  (4): ReLU()                       (4): ReLU()
                  (5): Conv1d(128, 256)             (5): Conv2d(128, 256)
                  (6): GlobalMaxPool()              (6): GlobalMaxPool()
                  (7): Linear(256, 10)              (7): Linear(256, 10)
                )                                 )

As you can see both modules "compiled" into original pytorch layers.

Custom modules with shape inference capabilities

User can define any module and make it shape inferable with torchlayers.Infer decorator class:

@torchlayers.Infer() # Remember to instantiate it
class MyLinear(torch.nn.Module):
    def __init__(self, in_features: int, out_features: int):
        self.weight = torch.nn.Parameter(torch.randn(in_features, out_features))
        self.bias = torch.nn.Parameter(torch.randn(out_features))

    def forward(self, inputs):
        return torch.nn.functional.linear(inputs, self.weight, self.bias)

layer = MyLinear(out_features=32)
# build and just like before

By default inputs.shape[1] will be used as in_features value during initial forward pass. If you wish to use different index (e.g. to infer using inputs.shape[3]) use @torchlayers.Infer(index=3) as a decorator

Autoencoder with inverted residual bottleneck and pixel shuffle

Please check code comments and documentation if needed. If you are unsure what autoencoder is you could see this example blog post.

Below is a convolutional denoising autoencoder example for ImageNet-like images. Think of it like a demonstration of capabilities of different layers and building blocks provided by torchlayers.

# Input - 3 x 256 x 256 for ImageNet reconstruction
class AutoEncoder(torch.nn.Module):
    def __init__(self):
        self.encoder = torchlayers.Sequential(
            torchlayers.StandardNormalNoise(),  # Apply noise to input images
            torchlayers.Conv(64, kernel_size=7),
            torchlayers.activations.Swish(),  # Direct access to module .activations
            torchlayers.AvgPool(),  # shape 64 x 128 x 128, kernel_size=2 by default
            torchlayers.HardSwish(),  # Access simply through torchlayers
            torchlayers.SeparableConv(128),  # Up number of channels to 128
            torchlayers.InvertedResidualBottleneck(),  # Default with squeeze excitation
            torchlayers.AvgPool(),  # shape 128 x 64 x 64, kernel_size=2 by default
            torchlayers.DepthwiseConv(256),  # DepthwiseConv easier to use
            # Pass input thrice through the same weights like in PolyNet
            torchlayers.Poly(torchlayers.InvertedResidualBottleneck(), order=3),
            torchlayers.ReLU(),  # all torch.nn can be accessed via torchlayers
            torchlayers.MaxPool(),  # shape 256 x 32 x 32
            torchlayers.Fire(out_channels=512),  # shape 512 x 32 x 32
            torchlayers.MaxPool(),  # shape 512 x 16 x 16
            # Randomly switch off the last two layers with 0.5 probability
            torchlayers.AvgPool(),  # shape 512 x 8 x 8

        # This one is more "standard"
        self.decoder = torchlayers.Sequential(
            torchlayers.Poly(torchlayers.InvertedResidualBottleneck(), order=2),
            # Has ICNR initialization by default after calling `build`
            torchlayers.ConvPixelShuffle(out_channels=512, upscale_factor=2),
            # Shape 512 x 16 x 16 after PixelShuffle
            torchlayers.Poly(torchlayers.InvertedResidualBottleneck(), order=3),
            torchlayers.ConvPixelShuffle(out_channels=256, upscale_factor=2),
            # Shape 256 x 32 x 32
            torchlayers.Poly(torchlayers.InvertedResidualBottleneck(), order=3),
            torchlayers.ConvPixelShuffle(out_channels=128, upscale_factor=2),
            # Shape 128 x 64 x 64
            torchlayers.Poly(torchlayers.InvertedResidualBottleneck(), order=4),
            torchlayers.ConvPixelShuffle(out_channels=64, upscale_factor=2),
            # Shape 64 x 128 x 128
            torchlayers.Dropout(),  # Defaults to 0.5 and Dropout2d for images
            torchlayers.ConvPixelShuffle(out_channels=32, upscale_factor=2),
            # Shape 32 x 256 x 256
            # Shape 3 x 256 x 256

    def forward(self, inputs):
        return self.decoder(self.encoder(inputs))

Now one can instantiate the module and use it with torch.nn.MSELoss as per usual.

autoencoder =, torch.randn(1, 3, 256, 256))



Latest release:

pip install --user torchlayers


pip install --user torchlayers-nightly


CPU standalone and various versions of GPU enabled images are available at dockerhub.

For CPU quickstart, issue:

docker pull szymonmaszke/torchlayers:18.04

Nightly builds are also available, just prefix tag with nightly_. If you are going for GPU image make sure you have nvidia/docker installed and it's runtime set.

torchlambda full description

Version PyPI Python PyTorch Docker
Version Py at least of version `17.05` is required.PI Python PyTorch Docker

torchlambda is a software designed to deploy PyTorch models on Amazon's AWS Lambda cloud service using AWS SDK for C++ and custom C++ runtime.

Using static compilation size of source code is only 30 Mb with all necessary dependencies. This allows users to pass their models as AWS Lambda layers, hence no other dependencies like Amazon S3 are required.

Comparison with other deployment tools

Improve this comparison's reliability via Pull Request, thanks. Also show guys below some love by visiting their projects (just click on the name).

Trait / Tool torchlambda fastai Lambda KubeFlow Tensorflow Serving
Autoscaling yes yes with Kubernetes with Kubernetes
Light/Heavy load Light Light Heavy/Both Both
GPU Support no no yes yes
Serverless yes yes no no
Required services AWS Lambda AWS Lambda, AWS S3 Kubernetes Cluster & cloud provider Deployable in various settings
Multiple frameworks no no yes no
Latest framework 1 :heavy_check_mark: :x: :x: :heavy_check_mark:
Version (higher more mature) 0.1.0 N/A 1.0 2.1.0
Customizable dependencies 2 yes no no no
Deployment size 3 ~30Mb +1Gb N/A ~67Mb4


  • Docker (at least version 17.05) is required. See Official Docker's documentation for installation instruction for your operating system.

  • Install torchlambda through pip, Python version 3.6 or higher is needed. You could also install this software within conda or other virutal environment of your choice. Following command should be sufficient:

    $ pip install --user torchlambda

Example deploy

Here is an example of ResNet18 model deployment using torchlambda. Run and create all necessary files in the same directory.

1. Create model to deploy

Below is a code ( to load ResNet from torchvision and compile is to torchscript:

import torch
import torchvision

model = torchvision.models.resnet18()

# Smaller example
example = torch.randn(1, 3, 64, 64)
script_model = torch.jit.trace(model, example)"model.ptc")

Invoke it from CLI:

$ python

You should get model.ptc in your current working directory.

2. Create deployment code with torchlambda scheme

Writing C++ code might be hard, hence torchlambda provides you a basic scheme where all one has to do is to input appropriate shapes for inference (either passed during request or hard-coded).

Run following command:

$ torchlambda scheme

You should see a new folder called torchlambda in your current directory. Contents of torchlambda/main.cpp are the ones you would usually modify.

Usually this code won't change too much, maybe additional fields parsing and aforementioned input shape.

If you wish to see the generated C++ scheme code (around 100 heavy-commented code) click below:

Click here to check generated code

Code below should be quite easy to follow. Check comments if in doubt or request improvements in Issues or make a Pull Request if you have an idea to make this section even easier.

#include <algorithm>
#include <iterator>

#include <aws/core/Aws.h>
#include <aws/core/utils/base64/Base64.h>
#include <aws/core/utils/json/JsonSerializer.h>
#include <aws/core/utils/memory/stl/AWSString.h>

#include <aws/lambda-runtime/runtime.h>

#include <torch/script.h>
#include <torch/torch.h>

static aws::lambda_runtime::invocation_response
handler(torch::jit::script::Module &module,
        const Aws::Utils::Base64::Base64 &transformer,
        const aws::lambda_runtime::invocation_request &request) {

  /* Name of field containing base64 encoded data */
  const Aws::String data_field{"data"};


  const auto json = Aws::Utils::Json::JsonValue{request.payload};
  if (!json.WasParseSuccessful())
    return aws::lambda_runtime::invocation_response::failure(
        "Failed to parse input JSON file.", "InvalidJSON");

  const auto json_view = json.View();
  if (!json_view.KeyExists(data_field))
    return aws::lambda_runtime::invocation_response::failure(
        "Required data was not provided.", "InvalidJSON");


  const auto base64_data = json_view.GetString(data_field);
  Aws::Utils::ByteBuffer decoded = transformer.Decode(base64_data);

  /* Copy data and move it to tensor (is there an easier way?) */
  /* Array holds channels * width * height, input your values below */
  float data[3 * 64 * 64];
            decoded.GetUnderlyingData() + decoded.GetLength() - 1, data);

  torch::Tensor tensor =
                           static_cast<long int>(decoded.GetLength()),
          /* Input your data shape for reshape including batch */
          .reshape({1, 3, 64, 64})
          .toType(torch::kFloat32) /

  /* Normalize tensor with ImageNet mean and stddev */
  torch::Tensor normalized_tensor = torch::data::transforms::Normalize<>{
      {0.485, 0.456, 0.406}, {0.229, 0.224, 0.225}}(tensor);


  /* {} will be casted to std::vector<torch::jit::IValue> under the hood */
  auto output = module.forward({normalized_tensor}).toTensor();
  const int label = torch::argmax(output).item<int>();

  /* Return JSON with field label containing predictions*/
  return aws::lambda_runtime::invocation_response::success(
          .WithInteger("label", label)

int main() {
  /* Inference doesn't need gradient, let's turn it off */
  torch::NoGradGuard no_grad_guard{};

  /* Change name/path to your model if you so desire */
  /* Layers are unpacked to /opt, so you are better off keeping it */
  constexpr auto model_path = "/opt/model.ptc";

  /* You could add some checks whether the module is loaded correctly */
  torch::jit::script::Module module = torch::jit::load(model_path, torch::kCPU);


   *                        INITIALIZE AWS SDK
   *                    & REGISTER REQUEST HANDLER

  Aws::SDKOptions options;
    const Aws::Utils::Base64::Base64 transformer{};
    const auto handler_fn =
         &transformer](const aws::lambda_runtime::invocation_request &request) {
          return handler(module, transformer, request);
  return 0;

3. Package your source with torchlambda deploy

Now we have our model and source code. It's time to deploy it as AWS Lambda ready .zip package.

Run from command line:

$ torchlambda deploy ./torchlambda --compilation "-Wall -O2"

Above will create file ready for deploy. Notice --compilation where you can pass any C++ compilation flags (here -O2 for performance optimization).

There are many more things one could set during this step, check torchlambda deploy --help for full list of available options (some, like --pytorch might trigger build of totally new Docker image, by default named torchlambda:custom. This takes a while and is quite CPU heavy so watch out and read --help).

4. Package your model as AWS Lambda Layer

As the above source code is roughly 30Mb in size (AWS Lambda has 250Mb limit), we can put our model as additional layer. To create it run:

$ torchlambda model ./model.ptc --destination ""

You will receive layer in your current working directory (--destination is optional).

5. Deploy to AWS Lambda

From now on you could mostly follow tutorial from AWS Lambda's C++ Runtime. It is assumed you have AWS CLI configured, if not check Configuring the AWS CLI.

5.1 Create trust policy JSON file

First create the following trust policy JSON file:

$ cat trust-policy.json
 "Version": "2012-10-17",
  "Statement": [
      "Effect": "Allow",
      "Principal": {
        "Service": [""]
      "Action": "sts:AssumeRole"

5.2 Create IAM role trust policy JSON file

Run from your shell:

$ aws iam create-role --role-name demo --assume-role-policy-document file://trust-policy.json

Note down the role Arn returned to you after running that command, it will be needed during next step.

5.3 Create AWS Lambda function

Create deployment function with the script below:

$ aws lambda create-function --function-name demo \
  --role <specify role arn from step 5.2 here> \
  --runtime provided --timeout 30 --memory-size 1024 \
  --handler torchlambda --zip-file fileb://

5.4 Create AWS Layer containing model

We already have our ResNet18 packed appropriately, run the following:

$ aws lambda publish-layer-version --layer-name model \
  --description "Resnet18 neural network model" \
  --license-info "MIT" \
  --zip-file fileb://

Please save the LayerVersionArn similar to step 5.2 and insert it below to add this layer to function from step 5.3:

$ aws lambda update-function-configuration \
  --function-name demo \
  --layers <specify layer arn from above here>

6. Encode image with base64 and request your function

Following script (save it as will send image-like tensor encoded using base64 via aws lambda invoke to test our function.

import base64
import shlex
import struct
import subprocess
import sys

import numpy as np

# Random image-like data
data = np.random.randint(low=0, high=255, size=(3, 64, 64)).flatten().tolist()
# Encode using bytes for AWS Lambda compatibility
image = struct.pack("<{}B".format(len(data)), *data)
encoded = base64.b64encode(image)
command = """aws lambda invoke --function-name %s --payload '{"data":"%s"}' %s""" % (

Run above script:

$ python demo output.txt

You should get the following response in output.txt (your label may vary as the image is just a random tensor):

cat output.txt
  {"label": 40}

Congratulations, you have deployed ResNet18 classifier using only AWS Lambda in 6 steps!


1. Support for latest version of it's main DL framework or main frameworks if multiple supported

2. Project dependencies shape can be easily cutomized. In torchlambda case it is customizable build of libtorch and AWS C++ SDK

3. Necessary size of code and dependencies to deploy model

4. Based on Dockerfile size

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