Caffe

caffe的单元 Blobs, layers, nets

- Blob

Blob作为caffe的存储及通信单元，是一个要被处理的真实数据（i.e. image batches, model parameters, derivatives for optimization）的封装。

Blob存储图像batch的方式为 (数目N)×(通道K)×(高H)×(宽W)，以行优先方式存储，也就是说，`(n,k,h,w)`物理地址为`((n*K+k)*H+h)*W+w`.

起初， CAFFE 只支持 4-D blob 和 2-D 卷积(NxCxHxW),现在支持 n-D blobs 和 (n-2)-D 卷积。

- Layer

Layers category

- Data layer

Image Data
Database
HDF Input
HDF Output
Input
Window Data
Memory Data
Dummy Data
Python

- Vision layer

Convolution

  layer {
      name: "conv1"
      type: "Convolution"
      bottom: "data"
      top: "conv1"
      # learning rate and decay multipliers for the filters
      param { lr_mult: 1 decay_mult: 1 }
      # learning rate and decay multipliers for the biases
      param { lr_mult: 2 decay_mult: 0 }
      convolution_param {
        num_output: 96     # learn 96 filters
        kernel_size: 11    # each filter is 11x11
        stride: 4          # step 4 pixels between each filter application
        pad: 0             # pad up pixels
        weight_filler {
          type: "gaussian" # initialize the filters from a Gaussian
          std: 0.01        # distribution with stdev 0.01 (default mean: 0)
        }
        bias_filler {
          type: "constant" # initialize the biases to zero (0)
          value: 0
        }
      }
    }

weight_filter type: caffe 中支持的初始化filter类型有

  constant, 
  gaussian,  
  positive_unitball,
  xavier, 
  msra, 
  bilinear,  
  uniform

默认类型为 constant, 更详细的介绍见 include/caffe/filter.hpp

Pooling

  layer {
    name: "pool1"
    type: "Pooling"
    bottom: "conv1"
    top: "pool1"
    pooling_param {
      pool: MAX
      kernel_size: 3 # pool over a 3x3 region
      stride: 2      # step two pixels (in the bottom blob) between pooling regions
    }
  }

Spatial Pyramid Pooling(SPP)
Local Response Normalization(LRN)
Crop
```
  layer {
      bottom: "A"
      bottom: "B"
      top: "C"
      name: "crop_u1u2"
      type: "Crop"
  }
```
CROP层用于裁剪数据。假设A、B层size分别为(20,50,512,512),(20,10,256,256)，则输出层C的size是(20,10,256,256), 更详细解释见crop.
Im2col
Deconvolution layer(transpose convolution)

same as Convolution layer

- Recurrent Layers

Recurrent
RNN
Long-Short Term Memory(LSTM)

- Common Layers

Inner Product - fully connected layer
Dropout
Embed

- Normalization Layers

Local Response Normalization(LRN)
Mean Variance Normalization(MVN)
Batch Normalization

- Activation Layers

ReLU and Leaky-ReLU
PReLU
ELU
Sigmoid
TanH
Absolute Value
Power- f(x)=(shift+scale*x)^power
Exp- f(x)=base^(shift+scale*x)
Log- f(x)=log(x)
BNLL- f(x)=log(1+exp(x))
Threshold
Bias
Scale

- Utility Layers

Flatter
Reshape
Batch Reindex
Split

Concat
```
 layer {
     bottom: "A"
     bottom: "B"
     top: "C"
     name: "concat_AB_C"
     type: "Concat"
     concat_param {
         axis: 1
     }
 }   
```
假设 A、B 的 size 分别为 (n1, c1, h, w), (n2, c2, h, w)，如果 axis=0, 则 C 的 size 为(n1+n2, c1, h, w) 且要求 c1=c2; 如果 axis=1, 则 C 的 size 为 (n1, c1+c2, h, 2) 且要求 n1=n2.
Slicing

Eltwise

适用于残差学习(Residual Learning)，实现 f(x) + x

 layer {
     bottom: "conv10"
     bottom: "conv11"
     top: "Res"
     name: "Res"
     type: "Eltwise"
     eltwise_param {
         op: SUM
         coeff: 1
         coeff: -1
     }
 }

Filter/Mask
Parameter
Reduction
Silence
ArgMax
Softmax
Python-allows custom Python layers

- Loss Layers

Multinomial Logistic Loss
Infogain Loss

Softmax with loss

 layer{
     name: "loss"
     type: "SoftmaxWithLoss"
     bottom: "pred"
     bottom: "label"
     top: "loss"
 }

Euclidean
Hinge/Margin

Sigmoid Cross-Entropy Loss

 layer{
     name: "loss"
     type: "SigmoidCrossEntropyLoss"
     bottom: "pred"
     bottom: "label"
     top: "loss"
 }

Accuracy/Top-k layer
Contrastive Loss

Multiple loss layers

事实上，一个网络可以包含很多 loss function, 只要它是一个 DAG (directed acyclic graph)(Caffe net本身可以是任何结构的DAG，不一定是线性结构)。例如:

    layers {
        name: "recon-loss"
        type: "Euclidean"
        bottom: "reconstructions"
        bottom: "data"
        top: "recon-loss"
    }
    layers {
        name: "class-loss"
        type: "softmaxWithLoss"
        bottom: "class-preds"
        bottom: "class-labels"
        top: "class-loss"
        loss_weight: 100.0
    }

表示的 Loss function 就是:
[图片上传失败...(image-f7d5fd-1515046033856)]

任何 layer 都可以产生 loss
[图片上传失败...(image-ba13f5-1515046033856)]

- Net

    name: "LogReg"
    layer {
      name: "mnist"
      type: "Data"
      top: "data"
      top: "label"
      data_param {
        source: "input_leveldb"
        batch_size: 64
      }
    }
    layer {
      name: "ip"
      type: "InnerProduct"
      bottom: "data"
      top: "ip"
      inner_product_param {
        num_output: 2
      }
    }
    layer {
      name: "loss"
      type: "SoftmaxWithLoss"
      bottom: "ip"
      bottom: "label"
      top: "loss"
    }

- Net visualization

Netscope

~/caffe/python/draw_net.py yout_net.prototxt yoursave.png

- Solver

solver_type: SGD
[图片上传失败...(image-6c3951-1515046033856)]

solver_type: NESTEROV
[图片上传失败...(image-e8f5cd-1515046033856)]

solver_type: ADAGRAD
[图片上传失败...(image-58b7b4-1515046033856)]

[图片上传失败...(image-d1791d-1515046033856)]

- Weight sharing

[图片上传失败...(image-d0591c-1515046033856)]

caffe 使用问题集锦

Q1 训练过程中人为中断训练(ctrl+C)，可否从中断时刻继续训练？

Answer: 可以。
```
 caffe train -solver solver.prototxt -snapshot train_1000.solverstate
```
以上示例表示从第1000步迭代继续训练。Training-and-Resuming
Q2 如何可视化卷积层？

caffe 与 python 、matlab 接口

- 使用 python 接口可视化卷积层以及做相关的 test ( [jupyter](http://nbviewer.jupyter.org/github/BVLC/caffe/blob/master/examples/00-classification.ipynb) ). 不过需要预装 Python 的一些包，如 numpy, scikit-learn等，才能正常 `import caffe`.

        sudo apt-get install python-numpy python-matplotlib python-sklearn python-scipy python-skimage python-h5py python-protobuf python-leveldb python-networkx python-nose python-pandas python-gflags Cython ipython
        sudo apt-get update
参考 [caffe examples](http://nbviewer.jupyter.org/github/BVLC/caffe/tree/master/examples/), 我们把 .ipynb 文件转换为 .py 文件并用 ipyhon 执行， 如果用 python 执行会出现 [错误](https://stackoverflow.com/questions/32538758/nameerror-name-get-ipython-is-not-defined)。

        jupyter nbconvert --to script '00-classfication.ipynb'
        ipython 00-classfication.py
但用ipython仍然遇到了一个 ImportError 的错误

[图片上传失败...(image-82cc64-1515046033856)]

[mnist](http://caffe.berkeleyvision.org/gathered/examples/mnist.html)

Q3 什么样的 layer 才能它的 bottom 和 top 可以是相同的名称？

Answer: 目前只有 Relu 层它的上下层可以使用相同名称，因为它是 element-wise 的，所以可以使用 in-place 的操作以节省内存。 (具体)

------------------------------------

caffe matlab接口使用

读取训练好的net参数

    caffe.reset_all();
    clear; close all;

    % settings
    model = '*.prototxt'
    weights = '*.caffemodel'

    % load model using mat_caffe
    net = caffe.Net(model, weights, 'test');

在界面中可以看到，net 含有以下参数
[图片上传失败...(image-dec443-1515046033856)]

BatchNorm 层的三个blob含义分别为 MEAN, VARIANCE, MOVING AVERAGE FACTOR

caffe python 接口使用

首先我们定义一个简单的卷积网络

name: "myconvnet"
input: "data"
input_dim: 1
input_dim: 1
input_dim: 256
input_dim: 256

layer {
  name: "conv"
  type: "Convolution"
  bottom: "data"
  top: "conv"
  convolution_param {
    num_output: 10
    kernel_size: 3
    stride: 1
    weight_filler {
      type: "gaussian"
      std: 0.01
    }
    bias_filler {
      type: "constant"
      value: 0
    }
  }
}

为了保证自己定义的网络各层之间的连接没有问题，我们可以将它可视化来检查网络，看它是什么样子的。这需要安装一些依赖的包

$ pip insall pydot
$ sudo apt-get install graphviz libgraphviz-dev
$ pip install pygraphviz

然后，就可以用 caffe 自带的 python 脚本画出自定义的网络

$ python /path/to/caffe/python/draw_net.py myconvnet.prototxt myconvnet.png

打开 myconvnet.png 就可以看到画出的网络
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下面说一说怎么用 Python 调用训练好的网络来做测试。首先，创建一个 net 对象来容纳我们的卷积网络:

impoort sys
sys.path.insert(0, '/path/to/caffe/python')
import numpy as np
import cv2
from pylab import *  #画图

import caffe
#initialize
caffe.set_device(1)     #指定使用哪一块GPU
caffe.set_mode_gpu()    #指定GPU计算

model_def = 'deploy.prototxt'   #给定网络模型
model_weight = 'net.cafffemodel'    #给定参数
net = caffe.Net(model_def, model_weight, caffe.TEST)        #给定phase = TEST, 那么网络只会向前计算，不会 backpropagation

Caffe

Caffe

caffe的单元 Blobs, layers, nets

- Blob

- Layer

- Data layer

- Vision layer

- Recurrent Layers

- Common Layers

- Normalization Layers

- Activation Layers

- Utility Layers

- Loss Layers

Multiple loss layers

- Net

- Net visualization

- Solver

- Weight sharing

caffe 使用问题集锦

------------------------------------

caffe matlab接口使用

caffe python 接口使用

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