Add English-version README (#24)

README.md

 
+# PaddleSlim
+
+As a submodule of PaddlePaddle framework, PaddleSlim is an open-source library for deep model compression and architecture search. PaddleSlim supports current popular deep compression techniques such as pruning, quantization, and knowledge distillation. Further, it also automates the search of hyperparameters and the design of lightweight deep architectures. In the future, we will develop more practically useful compression techniques for industrial-level applications and transfer these techniques to models in NLP.
+
+## Outline
+- Key Features
+- Architecture of PaddleSlim
+- Methods
+- Experimental Results
+
+## Key Features
+
+The main key features of PaddleSlim are:
+
+### Simple APIs
+
+- It provides simple APIs for building and deploying lightweight and energy-efficient deep models on different platforms. Experimental hyperparameters can be set up by a simple configuration file.
+- It requires just a little coding work for a model compression.
+
+### Outstanding Performance
+
+- For MobileNetV1 with limited redundancy, channel-based pruning can ensure lossless compression.
+- Knowledge distillation can promote the performance of baseline models with a clear margin.
+- Quantization after knowledge distillation can reduce model size and increase accuracy of models.
+
+### Flexible APIs
+
+- We automate the pruning process.
+- Pruning strategy can be applied onto various deep architectures.
+- We can distill multiple kinds of knowledge from teacher models to student models and self-defined losses for the corresponding knowledge distillation are supported.
+- We support the deployment of multiple compression strategies.
+
+## Architecture of PaddleSlim
+To make the usage of PaddleSlim clearer and easier, we briefly introduce the background of how to implement the library.
+
+The architecture of PaddleSlim is demonstrated in **Figure 1**. The high-level APIs often depend on several low-level APIs. We can see, knowledge distillation, quantization, and pruning are indirectly based on the Paddle framework. Currently, as a part of PaddlePaddle, user can use PaddleSlim for model compression and search after kindly download and install Paddle framework.
+
+<p align="center">
+<img src="docs/images/framework_0.png" height=452 width=900 hspace='10'/> <br />
+<strong>Figure 1</strong>
+</p>
+
+As shown in **Figure 1**, the top-level module, marked as yellow, is the API exposed to users. When we deploy compression methods in Python, we only need to construct an instance of Compressor.
+
+We encapsulate each compression and search method to a compression strategy class. When we train the deep model to be compressed, the strategy class will be instantiated by using the configuration information registered by users, as shown in **Figure 2**. The logic of training process is encapsulated in our compression method. The jobs that users should do by themself is to define the structure of deep models, to prepare the training data, and to choose optimization strategy. This would surely help users save much effort.
+
+<p align="center">
+<img src="docs/images/framework_1.png" height=255 width=646 hspace='10'/> <br />
+<strong>Figure 2</strong>
+</p>
+
+## Methods
+
+### Pruning
+
+- Here, PaddleSlim supports uniform prunning, sensitivity-based prunning, and automated model pruning methods.
+- PaddleSlim supports pruning of various deep architectures such as VGG, ResNet, and MobileNet.
+- PaddleSlim supports self-defined range of pruning, i.e., layers to be pruned.
+
+### Quantization
+
+- PaddleSlim supports training-aware quantization with static and dynamic estimation of quantization hyperparameters such as scale.
+  - Dynamic strategy: During inference, we quantize models with hyperparameters dynamically estimated from small batches of samples.
+  - Static strategy: During inference, we quantize models with the same hyperparameters estimated from training data.
+- PaddleSlim supports layer-wise and channel-wise quantization.
+- PaddleSlim provides models compatible with Paddle Mobile for final inference.
+
+### Knowledge Distillation
+
+- PaddleSlim supports the following losses added on any paired layers between teacher and student models:
+  - Flow of the solution procedure (FSP) loss.
+  - L2 loss.
+  - Softmax with cross-entropy loss.
+
+### Lightweight Network Architecture Search (Light-NAS)
+
+- PaddleSlim provides Simulated Annealing (SA)-based lightweight network architecture search method.
+  - PaddleSlim supports distributed search.
+  - PaddleSlim supports FLOPs and latency constrained search.
+  - PaddleSlim supports the latency estimation on different hardware and platforms.
+
+## Experimental Results
+
+In this section, we will show some experimental results conducted on PaddleSlim.
+
+### Quantization
+
+We evaluate the quantized models on ImageNet2012. The top-5/top-1 accuracies are compared,
+
+| Model | FP32| int8(X:abs_max, W:abs_max) | int8, (X:moving_average_abs_max, W:abs_max) |int8, (X:abs_max, W:channel_wise_abs_max) |
+|:---|:---:|:---:|:---:|:---:|
+|MobileNetV1|89.54%/70.91%|89.64%/71.01%|89.58%/70.86%|89.75%/71.13%|
+|ResNet50|92.80%/76.35%|93.12%/76.77%|93.07%/76.65%|93.15%/76.80%|
+
+Before and after quantization, the model sizes are,
+
+| Model       | FP32  | int8(A:abs_max, W:abs_max) | int8, (A:moving_average_abs_max, W:abs_max) | int8, (A:abs_max, W:channel_wise_abs_max) |
+| :---        | :---: | :---:                      | :---:                                       | :---:                                     |
+| MobileNetV1 | 17M   | 4.8M(-71.76%)               | 4.9M(-71.18%)                                | 4.9M(-71.18%)                              |
+| ResNet50    | 99M   | 26M(-73.74%)                | 27M(-72.73%)                                 | 27M(-72.73%)                               |
+
+Note: abs_max refers to dynamic strategy; moving_average_abs_max refers to static strategy; channel_wise_abs_max refers channel-wise quantization for weights in convolutional layers.
+
+### Pruning
+
+Data: ImageNet2012
+Baseline model: MobileNetV1
+Model size: 17M
+Top-5/top-1 accuracies: 89.54% / 70.91%
+
+#### Uniform pruning
+
+| FLOPS |model size| Decrease in accuracy (top5/top1)| Accuracy (top5/top1) |
+|---|---|---|---|
+| -50%|-47.0%(9.0M)|-0.41% / -1.08%|88.92% / 69.66%|
+| -60%|-55.9%(7.5M)|-1.34% / -2.67%|88.22% / 68.24%|
+| -70%|-65.3%(5.9M)|-2.55% / -4.34%|86.99% / 66.57%|
+
+#### Sensitivity-based pruning
+
+| FLOPS |精度（top5/top1）|
+|---|---|
+| -0%  |89.54% / 70.91% |
+| -20% |90.08% / 71.48% |
+| -36% |89.62% / 70.83%|
+| -50% |88.77% / 69.31%|
+
+### Knowledge distillation
+
+Data: ImageNet2012
+Baseline model: MobileNetV1
+
+|- |Accuracy (top5/top1) |Gain in accuracy (top5/top1)|
+|---|---|---|
+| Train from scratch | 89.54% / 70.91%| - |
+| Distilled from ResNet50 | 90.92% / 71.97%| +1.28% / +1.06%|
+
+### Hydrid methods
+
+Data: ImageNet2012
+Baseline model: MobileNetV1
+
+|Methods |Accuracy (top5/top1) |Model Size|
+|---|---|---|
+| Baseline|89.54% / 70.91%|17.0M|
+| Distilled from ResNet50|90.92% / 71.97%|17.0M|
+| Distilled from ResNet50 + Quantization |90.94% / 72.01%|4.8M|
+| Pruning -50% FLOPS|89.13% / 69.83%|9.0M|
+| Pruning -50% FLOPS + Quantization|89.11% / 69.20%|2.3M|
+
+### Light-NAS
+
+Data: ImageNet2012
+
+| -                | FLOPS | Top1/Top5 accuracy | GPU cost             |
+|------------------|-------|--------------------|----------------------|
+| MobileNetV2      | 0%    | 71.90% / 90.55%    | -                    |
+| Light-NAS-model0 | -3%   | 72.45% / 90.70%    | 1.2K GPU hours(V100) |
+| Light-NAS-model1 | -17%  | 71.84% / 90.45%    | 1.2K GPU hours(V100) |
+
+Hardware-aware latency-constrained light-NAS
+
+| -             | Latency | Top1/Top5 accuracy | GPU cost            |
+|---------------|---------|--------------------|---------------------|
+| MobileNetV2   | 0%      | 71.90% / 90.55%    | -                   |
+| RK3288  | -23%    | 71.97% / 90.35%    | 1.2K GPU hours(V100) |
+| Android cellphone  | -20%    | 72.06% / 90.36%    | 1.2K GPU hours(V100) |
+| iPhone 6s   | -17%    | 72.22% / 90.47%    | 1.2K GPU hours(V100) |
+
+
 
 # PaddleSlim