Model Deployment

The deployment of OpenMMLab codebases, including MMDetection, MMClassification and so on are supported by MMDeploy. The latest deployment guide for MMDetection can be found from here.

This tutorial is organized as follows:

Installation
Convert model
Model specification
Model inference
- Backend model inference
- SDK model inference
Supported models

Installation

Please follow the guide to install mmdet. And then install mmdeploy from source by following this guide.

If you install mmdeploy prebuilt package, please also clone its repository by 'git clone https://github.com/open-mmlab/mmdeploy.git --depth=1' to get the deployment config files.

Convert model

Suppose mmdetection and mmdeploy repositories are in the same directory, and the working directory is the root path of mmdetection.

Take Faster R-CNN model as an example. You can download its checkpoint from here, and then convert it to onnx model as follows:

from mmdeploy.apis import torch2onnx
from mmdeploy.backend.sdk.export_info import export2SDK

img = 'demo/demo.jpg'
work_dir = 'mmdeploy_models/mmdet/onnx'
save_file = 'end2end.onnx'
deploy_cfg = '../mmdeploy/configs/mmdet/detection/detection_onnxruntime_dynamic.py'
model_cfg = 'configs/faster_rcnn/faster-rcnn_r50_fpn_1x_coco.py'
model_checkpoint = 'faster_rcnn_r50_fpn_1x_coco_20200130-047c8118.pth'
device = 'cpu'

# 1. convert model to onnx
torch2onnx(img, work_dir, save_file, deploy_cfg, model_cfg,
           model_checkpoint, device)

# 2. extract pipeline info for inference by MMDeploy SDK
export2SDK(deploy_cfg, model_cfg, work_dir, pth=model_checkpoint,
           device=device)

It is crucial to specify the correct deployment config during model conversion. MMDeploy has already provided builtin deployment config files of all supported backends for mmdetection, under which the config file path follows the pattern:

{task}/{task}_{backend}-{precision}_{static | dynamic}_{shape}.py

{task}: task in mmdetection.

There are two of them. One is detection and the other is instance-seg, indicating instance segmentation.

mmdet models like RetinaNet, Faster R-CNN and DETR and so on belongs to detection task. While Mask R-CNN is one of instance-seg models.

DO REMEMBER TO USE detection/detection_*.py deployment config file when trying to convert detection models and use instance-seg/instance-seg_*.py to deploy instance segmentation models.

{backend}: inference backend, such as onnxruntime, tensorrt, pplnn, ncnn, openvino, coreml etc.
{precision}: fp16, int8. When it's empty, it means fp32
{static | dynamic}: static shape or dynamic shape
{shape}: input shape or shape range of a model

Therefore, in the above example, you can also convert Faster R-CNN to tensorrt-fp16 model by detection_tensorrt-fp16_dynamic-320x320-1344x1344.py.

When converting mmdet models to tensorrt models, --device should be set to "cuda"

Model specification

Before moving on to model inference chapter, let's know more about the converted model structure which is very important for model inference.

The converted model locates in the working directory like mmdeploy_models/mmdet/onnx in the previous example. It includes:

mmdeploy_models/mmdet/onnx
├── deploy.json
├── detail.json
├── end2end.onnx
└── pipeline.json

in which,

end2end.onnx: backend model which can be inferred by ONNX Runtime
*xxx*.json: the necessary information for mmdeploy SDK

The whole package mmdeploy_models/mmdet/onnx is defined as mmdeploy SDK model, i.e., mmdeploy SDK model includes both backend model and inference meta information.

Model inference

Backend model inference

Take the previous converted end2end.onnx model as an example, you can use the following code to inference the model and visualize the results.

from mmdeploy.apis.utils import build_task_processor
from mmdeploy.utils import get_input_shape, load_config
import torch

deploy_cfg = '../mmdeploy/configs/mmdet/detection/detection_onnxruntime_dynamic.py'
model_cfg = 'configs/faster_rcnn/faster-rcnn_r50_fpn_1x_coco.py'
device = 'cpu'
backend_model = ['mmdeploy_models/mmdet/onnx/end2end.onnx']
image = 'demo/demo.jpg'

# read deploy_cfg and model_cfg
deploy_cfg, model_cfg = load_config(deploy_cfg, model_cfg)

# build task and backend model
task_processor = build_task_processor(model_cfg, deploy_cfg, device)
model = task_processor.build_backend_model(backend_model)

# process input image
input_shape = get_input_shape(deploy_cfg)
model_inputs, _ = task_processor.create_input(image, input_shape)

# do model inference
with torch.no_grad():
    result = model.test_step(model_inputs)

# visualize results
task_processor.visualize(
    image=image,
    model=model,
    result=result[0],
    window_name='visualize',
    output_file='output_detection.png')

SDK model inference

You can also perform SDK model inference like following,

from mmdeploy_python import Detector
import cv2

img = cv2.imread('demo/demo.jpg')

# create a detector
detector = Detector(model_path='mmdeploy_models/mmdet/onnx',
                    device_name='cpu', device_id=0)
# perform inference
bboxes, labels, masks = detector(img)

# visualize inference result
indices = [i for i in range(len(bboxes))]
for index, bbox, label_id in zip(indices, bboxes, labels):
    [left, top, right, bottom], score = bbox[0:4].astype(int), bbox[4]
    if score < 0.3:
        continue

    cv2.rectangle(img, (left, top), (right, bottom), (0, 255, 0))

cv2.imwrite('output_detection.png', img)

Besides python API, mmdeploy SDK also provides other FFI (Foreign Function Interface), such as C, C++, C#, Java and so on. You can learn their usage from demos.

Supported models

Please refer to here for the supported model list.

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