batch inference

Batch Inference Toolkit

Batch Inference Toolkit(batch-inference) is a Python package that batches model input tensors coming from multiple requests dynamically, executes the model, un-batches output tensors and then returns them back to each request respectively. This will improve system throughput because of better compute parallelism and better cache locality. The entire process is transparent to developers.

When to use

When you want to host Deep Learning model inference on Cloud servers, especially on GPU

Why to use

It can improve your server throughput up to multiple times

Advantage of batch-inference

• Platform independent lightweight python library
• Only few lines code change is needed to onboard using built-in batching algorithms
• Flexible APIs to support customized batching algorithms and input types
• Support multi-process remote mode to avoid python GIL bottleneck
• Tutorials and benchmarks on popular models:

Model	Throughput Comparing to Baseline	Links
Bert Embedding	4.7x	Tutorial
GPT Completion	16x	Tutorial

Installation

Install from Pip

python -m pip install batch-inference --upgrade

Build and Install from Source (for developers)

git clone https://github.com/microsoft/batch-inference.git
python -m pip install -e .[docs,testing]

# if you want to format the code before commit
pip install pre-commit
pre-commit install

# run unittests
python -m unittest discover tests

Example

Let's start with a toy model to learn the APIs. Firstly, you need to define a predict_batch method in your model class, and then add the batching decorator to your model class.

The batching decorator adds host() method to create ModelHost object. The predict method of ModelHost takes a single query as input, and it will merge multiple queries into a batch before calling predict_batch method. The predict method also splits outputs from predict_batch method before it returns result.

import numpy as np
from batch_inference import batching
from batch_inference.batcher.concat_batcher import ConcatBatcher

@batching(batcher=ConcatBatcher(), max_batch_size=32)
class MyModel:
    def __init__(self, k, n):
        self.weights = np.random.randn(k, n).astype("f")

    # shape of x: [batch_size, m, k]
    def predict_batch(self, x):
        y = np.matmul(x, self.weights)
        return y

# initialize MyModel with k=3 and n=3
host = MyModel.host(3, 3)
host.start()

# shape of x: [1, 3, 3]
def process_request(x):
    y = host.predict(x)
    return y

host.stop()

Batcher is responsible to merge queries and split outputs. In this case ConcatBatcher will concat input tensors into a batched tensors at first dimension. We provide a set of built-in Batchers for common scenarios, and you can also implement your own Batcher. See What is Batcher for more information.