add quantization en tutorial (#99)

docs/en/quick_start/index_en.rst

@@ -6,4 +6,6 @@ Quick Start
    :maxdepth: 1
 
    pruning_tutorial_en.md
+   quant_aware_tutorial_en.md
+   quant_post_tutorial_en.md
     

docs/en/quick_start/quant_aware_tutorial_en.md

+# Training-aware Quantization of image classification model - quick start
+
+This tutorial shows how to do training-aware quantization using [API](https://github.com/PaddlePaddle/PaddleSlim/blob/develop/docs/docs/api/quantization_api.md) in PaddleSlim. We use MobileNetV1 to train image classification model as example. The tutorial contains follow sections:
+
+1. Necessary imports
+2. Model architecture
+3. Train normal model
+4. Quantization
+5. Train model after quantization
+6. Save model after quantization
+
+## 1. Necessary imports
+PaddleSlim depends on Paddle1.7. Please make true that you have installed Paddle correctly. Then do the necessary imports:
+
+```python
+import paddle
+import paddle.fluid as fluid
+import paddleslim as slim
+import numpy as np
+```
+
+## 2. Model architecture
+
+The section constructs a classification model, which use ``MobileNetV1`` and MNIST dataset. The model's input size is `[1, 28, 28]` and output size is 10. In order to show tutorial conveniently, we pre-defined a method to get image classification model in `paddleslim.models`.
+
+>note: The APIs in `paddleslim.models` are not formal inferface in PaddleSlim. They are defined to simplify the tutorial such as the definition of model structure and the construction of Program.
+
+
+```python
+exe, train_program, val_program, inputs, outputs = \
+    slim.models.image_classification("MobileNet", [1, 28, 28], 10, use_gpu=True)
+```
+
+## 3. Train normal model
+
+The section shows how to define model inputs, train and test model. The reason for training the normal image classification model first is that the quantization model's training process is performed on the well-trained model. We add quantization and dequantization operators in well-trained model and finetune using smaller learning rate.
+
+### 3.1 input data definition
+
+To speed up training process, we select MNIST dataset to train image classification model. The API `paddle.dataset.mnist` in Paddle framework contains downloading and reading the images in dataset.
+
+```python
+import paddle.dataset.mnist as reader
+train_reader = paddle.batch(
+        reader.train(), batch_size=128, drop_last=True)
+test_reader = paddle.batch(
+        reader.train(), batch_size=128, drop_last=True)
+train_feeder = fluid.DataFeeder(inputs, fluid.CPUPlace())
+```
+
+### 3.2 training model and testing
+
+Define functions to train and test model. We only need call the functions when formal model training and quantization model training. The function does one epoch training because that MNIST dataset is small and top1 accuracy will reach 95% after one epoch.
+
+```python
+def train(prog):
+    iter = 0
+    for data in train_reader():
+        acc1, acc5, loss = exe.run(prog, feed=train_feeder.feed(data), fetch_list=outputs)
+        if iter % 100 == 0:
+            print('train iter={}, top1={}, top5={}, loss={}'.format(iter, acc1.mean(), acc5.mean(), loss.mean()))
+        iter += 1
+
+def test(prog):
+    iter = 0
+    res = [[], []]
+    for data in train_reader():
+        acc1, acc5, loss = exe.run(prog, feed=train_feeder.feed(data), fetch_list=outputs)
+        if iter % 100 == 0:
+            print('test iter={}, top1={}, top5={}, loss={}'.format(iter, acc1.mean(), acc5.mean(), loss.mean()))
+        res[0].append(acc1.mean())
+        res[1].append(acc5.mean())
+        iter += 1
+    print('final test result top1={}, top5={}'.format(np.array(res[0]).mean(), np.array(res[1]).mean()))
+```
+
+Call ``train`` function to train normal classification model. ``train_program`` is defined in 2. Model architecture.
+
+```python
+train(train_program)
+```
+
+Call ``test`` function to test normal classification model. ``val_program`` is defined in 2. Model architecture.
+
+```python
+test(val_program)
+```
+
+
+## 4. Quantization
+
+We call ``quant_aware`` API to add quantization and dequantization operators in ``train_program`` and ``val_program`` according to [default configuration](https://paddlepaddle.github.io/PaddleSlim/api/quantization_api/#_1).
+
+```python
+quant_program = slim.quant.quant_aware(train_program, exe.place, for_test=False)
+val_quant_program = slim.quant.quant_aware(val_program, exe.place, for_test=True)
+```
+
+
+## 5. Train model after quantization
+
+Finetune the model after quantization. Test model after one epoch training.
+
+```python
+train(quant_program)
+```
+
+Test model after quantization. The top1 and top5 accuracy are close to result in ``3.2 training model and testing``. We preform the training-aware quantization without loss on this image classification model.
+
+```python
+test(val_quant_program)
+```
+
+
+## 6. Save model after quantization
+
+The model in ``4. Quantization`` after calling ``slim.quant.quant_aware`` API is only suitable to train. To get the inference model, we should use [slim.quant.convert](https://paddlepaddle.github.io/PaddleSlim/api/quantization_api/#convert) API to change model architecture and use [fluid.io.save_inference_model](https://www.paddlepaddle.org.cn/documentation/docs/zh/develop/api_cn/io_cn/save_inference_model_cn.html#save-inference-model) to save model. ``float_prog``'s parameters are float32 dtype but in int8's range which can be used in ``fluid`` or ``paddle-lite``. ``paddle-lite`` will change the parameters' dtype from float32 to int8 first when loading the inference model. ``int8_prog``'s parameters are int8 dtype and we can get model size after quantization by saving it. ``int8_prog`` cannot be used in ``fluid`` or ``paddle-lite``.
+
+
+```python
+float_prog, int8_prog = slim.quant.convert(val_quant_program, exe.place, save_int8=True)
+target_vars = [float_prog.global_block().var(name) for name in outputs]
+fluid.io.save_inference_model(dirname='./inference_model/float',
+        feeded_var_names=[var.name for var in inputs],
+        target_vars=target_vars,
+        executor=exe,
+        main_program=float_prog)
+fluid.io.save_inference_model(dirname='./inference_model/int8',
+        feeded_var_names=[var.name for var in inputs],
+        target_vars=target_vars,
+        executor=exe,
+        main_program=int8_prog)
+```

docs/en/quick_start/quant_post_tutorial_en.md

+# Post-training Quantization of image classification model - quick start
+
+This tutorial shows how to do post training quantization using [API](https://github.com/PaddlePaddle/PaddleSlim/blob/develop/docs/docs/api/quantization_api.md) in PaddleSlim. We use MobileNetV1 to train image classification model as example. The tutorial contains follow sections:
+
+1. Necessary imports
+2. Model architecture
+3. Train normal model
+4. Post training quantization
+
+## 1. Necessary imports
+PaddleSlim depends on Paddle1.7. Please make true that you have installed Paddle correctly. Then do the necessary imports:
+
+
+```python
+import paddle
+import paddle.fluid as fluid
+import paddleslim as slim
+import numpy as np
+```
+## 2. Model architecture
+
+The section constructs a classification model, which use ``MobileNetV1`` and MNIST dataset. The model's input size is `[1, 28, 28]` and output size is 10. In order to show tutorial conveniently, we pre-defined a method to get image classification model in `paddleslim.models`.
+
+>note: The APIs in `paddleslim.models` are not formal inferface in PaddleSlim. They are defined to simplify the tutorial such as the definition of model structure and the construction of Program.
+
+
+```python
+exe, train_program, val_program, inputs, outputs = \
+    slim.models.image_classification("MobileNet", [1, 28, 28], 10, use_gpu=True)
+```
+
+## 3. Train normal model
+
+The section shows how to define model inputs, train and test model. The reason for training the normal image classification model first is that the post training quantization is performed on the well-trained model.
+
+### 3.1 input data definition
+
+To speed up training process, we select MNIST dataset to train image classification model. The API `paddle.dataset.mnist` in Paddle framework contains downloading and reading the images in dataset.
+
+```python
+import paddle.dataset.mnist as reader
+train_reader = paddle.batch(
+        reader.train(), batch_size=128, drop_last=True)
+test_reader = paddle.batch(
+        reader.train(), batch_size=128, drop_last=True)
+train_feeder = fluid.DataFeeder(inputs, fluid.CPUPlace())
+```
+
+### 3.2 training model and testing
+
+Define functions to train and test model. We only need call the functions when formal model training and quantization model training. The function does one epoch training because that MNIST dataset is small and top1 accuracy will reach 95% after one epoch.
+
+```python
+def train(prog):
+    iter = 0
+    for data in train_reader():
+        acc1, acc5, loss = exe.run(prog, feed=train_feeder.feed(data), fetch_list=outputs)
+        if iter % 100 == 0:
+            print('train', acc1.mean(), acc5.mean(), loss.mean())
+        iter += 1
+
+def test(prog, outputs=outputs):
+    iter = 0
+    res = [[], []]
+    for data in train_reader():
+        acc1, acc5, loss = exe.run(prog, feed=train_feeder.feed(data), fetch_list=outputs)
+        if iter % 100 == 0:
+            print('test', acc1.mean(), acc5.mean(), loss.mean())
+        res[0].append(acc1.mean())
+        res[1].append(acc5.mean())
+        iter += 1
+    print('final test result', np.array(res[0]).mean(), np.array(res[1]).mean())
+```
+
+Call ``train`` function to train normal classification model. ``train_program`` is defined in 2. Model architecture.
+
+
+```python
+train(train_program)
+```
+
+Call ``test`` function to test normal classification model. ``val_program`` is defined in 2. Model architecture.
+
+```python
+test(val_program)
+```
+
+
+Save inference model. Save well-trained model in ``'./inference_model'``. We will load the model when doing post training quantization.
+
+
+```python
+target_vars = [val_program.global_block().var(name) for name in outputs]
+fluid.io.save_inference_model(dirname='./inference_model',
+        feeded_var_names=[var.name for var in inputs],
+        target_vars=target_vars,
+        executor=exe,
+        main_program=val_program)
+```
+
+## 4. Post training quantization
+
+Call ``slim.quant.quant_post`` API to do post training quantization. The API will load the inference model in ``'./inference_model'`` first and calibrate the quantization parameters using data in sample_generator. In this tutorial, we use 10 mini-batch data to calibrate the quantization parameters. There is no need to train model but run forward to get activations for quantization scales calculation. The model after post training quantization are saved in ``'./quant_post_model'``.
+
+```python
+slim.quant.quant_post(
+        executor=exe,
+        model_dir='./inference_model',
+        quantize_model_path='./quant_post_model',
+        sample_generator=reader.test(),
+        batch_nums=10)
+```
+
+Load the model after post training quantization in ``'./quant_post_model'`` and run ``test`` function. The top1 and top5 accuracy are close to result in ``3.2 training model and testing``. We preform the post training quantization without loss on this image classification model.
+
+```python
+quant_post_prog, feed_target_names, fetch_targets = fluid.io.load_inference_model(
+        dirname='./quant_post_model',
+        executor=exe)
+test(quant_post_prog, fetch_targets)
+```