CN108764472A - Convolutional neural networks fractional order error back propagation method - Google Patents

Convolutional neural networks fractional order error back propagation method Download PDF

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CN108764472A
CN108764472A CN201810490436.1A CN201810490436A CN108764472A CN 108764472 A CN108764472 A CN 108764472A CN 201810490436 A CN201810490436 A CN 201810490436A CN 108764472 A CN108764472 A CN 108764472A
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convolutional neural
neural networks
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赵丽玲
李远禄
张泽林
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Nanjing University of Information Science and Technology
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Nanjing University of Information Science and Technology
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Abstract

Convolutional neural networks fractional order error back propagation method of the present invention, includes the following steps:Step 1)Select convolutional neural networks model;Step 2)Network weight is updated using fractional order error back propagation method;Step 3)According to the network weight, convolutional neural networks parameter is obtained.Advantageous effect:The integer order derivative of activation primitive during error back propagation is become into Fractional Derivative, fractional order derivation model advantage more accurate than integer rank derivation model is played, " gradient disappearance " problem during error back propagation has been effectively relieved, improve the training effectiveness of convolutional neural networks, so that convolutional neural networks is realized preferably fitting for training data, improves the generalization ability of network.

Description

Convolutional neural networks fractional order error back propagation method
Technical field
The invention belongs to intelligent algorithm fields, more particularly to a kind of convolutional neural networks fractional order error reversely passes Broadcasting method.
Background technology
Convolutional neural networks are the algorithms of artificial intelligence field, and the image from the automobile of automatic Pilot to Google is searched, Convolutional neural networks can be used to realize.Training process is a very important part in convolutional neural networks, in the mistake Generally network weight (filter) is set to constantly update adjustment by back-propagation method in journey, until the output of network becomes with target In consistent.The process of back-propagation method is divided into 4 basic steps:Propagated forward, costing bio disturbance, backpropagation, weights are more Newly.However, in " backpropagation " step, usually will appear because " gradient disappearance " phenomenon causes network to be difficult to trained problem. Therefore, it is that convolutional neural networks are able to normal training to be effectively improved " gradient disappearance ", to obtain the important of precision net parameter Ensure.
Currently, the combination of fractional calculus and neural network has become the research hotspot of artificial intelligence field, fractional order The application of neural network shows the advantage for having bigger than traditional neural network.《Voice based on fractional order convolutional neural networks Recognizer research》(Zhang Lei Harbin University of Science and Technologys, 2016.) is directly handled activation primitive using fractional order method, Network training is participated in using fractional order activation primitive, improves the training speed of convolutional neural networks.《Fractional order theory is in BP god Through the application in network》(Chen little Lei Nanjing Forestry University, 2013.) convolutional neural networks train back-propagation process in, directly It connects and fractional order partial derivative is asked to error, and become the iterative learning of order, realize the switching of fractional-order and integer order With the adaptive adjustment of fractional-order so that the receipts precision that network training not only has convergence rate but also had.Patent application《It is a kind of The method for improving convolutional neural networks structure》(publication number:106960243 A of CN) fractional order maximum value pond principle is utilized, it will Maximum value pond layer Change All in traditional convolution neural network structure is fractional order, reaches the down-sampling of the arbitrary dimension of image Dimensionality reduction improves network training efficiency.Although above-mentioned algorithm has some superiority compared with traditional algorithm, the combination side of " loose " Formula does not probe into fractional order theory and convolutional neural networks theory combination the name of the game.Targetedly improve convolutional Neural The training process of network can just further increase network parameter precision, improve network performance.
Invention content
The purpose of the present invention is overcoming the shortcomings of above-mentioned background technology, fractional order and convolutional neural networks theory are realized It is " close " to combine, a kind of convolutional neural networks fractional order error back propagation method is provided, is specifically realized by following scheme:
The convolutional neural networks fractional order error back propagation method, includes the following steps:
Step 1) selects convolutional neural networks model;
Step 2) updates network weight using fractional order error back propagation method;
Step 3) obtains convolutional neural networks parameter according to the network weight.
The further design of the convolutional neural networks fractional order error back propagation method is that the step 1) is specific Including:
Step 1-1) setting neural network model, the neural network model include one layer of input layer, n-layer hidden layer and One layer of output layer, the input layer, hidden layer, output layer node number correspond to n respectively1, n2, 1;
Step 1-2) a large amount of high-definition picture { X of settingiAnd its corresponding low-resolution image { YiComposition training Collection, wherein:X indicates that high-definition picture, Y indicate that low-resolution image, i indicate image index;Step 1-3) setting convolution god Weights through network and it is biased to Θ={ W, B }, it is respectively L and σ to set error function and activation primitive, and wherein W indicates weights, B is biasing.
The further design of the convolutional neural networks fractional order error back propagation method is that the step 2 includes Following sub-step:
Step 2-1) netinit:Initialize network weight and biasing Θ={ W1,B1, maximum iteration is set;
Step 2-2) input training data { Xi,Yi};
Step 2-3) setting primary iteration number k=1;
Step 2-4) network weight is optimized;
Step 2-5) according to k=k+1 update iterations, and jump to step 2-4).
The convolutional neural networks fractional order error back propagation method it is further design be, step 2-4) to network Weights, which optimize, specifically includes following steps:
Step 2-4-1) calculate network output valve;
Step 2-4-2) calculate error:Using the error function, the error between network output valve and actual value is calculated, Whether error in judgement meets the requirements, if met the requirements, network training terminates to be transferred to step 3);If being unsatisfactory for requiring, Modified weight is carried out, 2-4-3 is entered step);
Step 2-4-3) Fractional Derivative of activation primitive in error back propagation gradient is calculated, and calculate each neuron The Fractional Derivative of node;
Step 2-4-4) calculate error gradient;
Step 2-4-5) correct weights:Gradient according to error about weight, corrective networks weights.
The convolutional neural networks fractional order error back propagation method it is further design be, the step 2-4-3) The middle Fractional Derivative that activation primitive in error back propagation gradient is calculated according to formula (1):
Wherein, GradlIndicate l layers of error back propagation gradient,For the input of activation primitive, i.e., The output of network node,Indicate the of (l-1) layerA neuron is connected toThe weight of j-th of neuron of layer,Indicate that the biasing of l layers of j-th of neuron, μ indicate that the order of Fractional Derivative, ⊙ are matrix corresponding position product, table Show point-to-point multiplying between matrix or vector;
The Fractional Derivative of each neuron node is calculated according to formula (2):
Wherein,For fractional order differential operator, D is 1 rank differential operator, and x indicates the output valve of neural network node, σ (x) indicate that activation primitive, σ ' (x) indicate that 1 order derivative of activation primitive, μ indicate that the order of fractional order differential, Γ (x) are Gamma Function is defined asAnd Re (x) > 0.
The convolutional neural networks fractional order error back propagation method it is further design be, step 2-4-5) use Classical stochastic gradient descent method corrects weights according to formula (3),
Wherein, i indicates that the network number of plies, η indicate learning rate, obtained by way of line search,Indicate activation The Fractional Derivative of function.
The convolutional neural networks fractional order error back propagation method it is further design be, step 1-3) in swash Function σ expression formulas such as formula (4) living:
Wherein, x is network node output valve.
Beneficial effects of the present invention are:
The convolutional neural networks fractional order error back propagation method of the present invention will activate letter during error back propagation Several integer order derivatives become Fractional Derivative, and it is more accurately more excellent than integer rank derivation model to have played fractional order derivation model Gesture has been effectively relieved " gradient disappearance " problem during error back propagation, has improved the training effectiveness of convolutional neural networks, So that convolutional neural networks is realized preferably fitting for training data, improves the generalization ability of network.
Description of the drawings
Fig. 1 is convolutional neural networks fractional order error back propagation method flow diagram provided by the invention.
Fig. 2 is that fractional order error backward propagation method model provided by the invention (every layer only there are one neurons) shows It is intended to.
Specific implementation mode
Below with reference to attached drawing, technical scheme of the present invention is described in detail.
As shown in Figure 1, the basic step of convolutional neural networks fractional order error back propagation method is as follows:
Step 1) selects convolutional neural networks model.
Step 2) updates network weight using fractional order error back propagation method.
Step 3) obtains convolutional neural networks parameter according to the network weight.
Preferably, step 1) the convolutional neural networks model of the present embodiment is as follows:
Step 1-1) four layers of neural network model of selection, including 1 layer of input layer, n-layer hidden layer, 1 layer of output layer be described defeated It is respectively n to enter layer, hidden layer, output layer node number1, n2, 1.
Step 1-2) a large amount of high-definition picture { X of selectioniAnd its corresponding low-resolution image { YiComposition training Collection.
Step 1-3) convolutional neural networks weights and biasing be denoted as Θ={ W1,W2,...,Wn+1,B1,B2,...,Bn+1, Error loses function and activation primitive is denoted as L and σ respectively.
It is further preferred that error function L expression formulas such as formula (1) in the step 1) of the present embodiment:
N is the quantity of training sample in formula, and F is high-low resolution image mapping function end to end,
F(Yi, Θ) and indicate that neural network forecast value, X indicate desired value.
It is further preferred that the activation primitive σ expression formulas in the step 1) of the present embodiment are:
Wherein, x is network node output valve.
Preferably, the step 2) of the present embodiment includes following sub-step:
Step 2-1) netinit.Network weight and biasing are initialized, it is 0 that wherein weight initialization, which is mean value, standard The Gaussian Profile that difference is 0.001, biasing are initialized as 0;Maximum iteration K is set;
Step 2-2) input training data { Xi,Yi};
Step 2-3) setting primary iteration number k=1;
Step 2-4) network weight is optimized;
Preferably, step 2-4) network weight is optimized includes the following steps:
Step 2-4-1) calculate network output valve;
Step 2-4-2) calculate error.Using the error function, the error between network output valve and actual value is calculated, Whether error in judgement meets the requirements.If met the requirements, network training terminates to be transferred to step 3;If being unsatisfactory for requiring, and repeatedly Generation number not up to sets maximum times K, then carries out modified weight, enter step 2-4-3;
Step 2-4-3) calculate error back propagation gradient in activation primitive Fractional Derivative.To each neuron node Using the Fractional Derivative of identical order;
Error back propagation gradient calculation expression is:
Wherein, GradlIndicate l layers of error back propagation gradient,For the input of activation primitive, i.e., The output of network node,Indicate the of (l-1) layerA neuron is connected toThe weight of j-th of neuron of layer,Indicate that the biasing of l layers of j-th of neuron, μ indicate that the order of Fractional Derivative, ⊙ are Hadamard product (matrixes pair Answer position product), point-to-point multiplying between representing matrix or vector;
Fractional Derivative calculation formula is:
Wherein,For fractional order differential operator, D is 1 rank differential operator, and x indicates the output valve of neural network node, σ (x) indicate that activation primitive, σ ' (x) indicate that 1 order derivative of activation primitive, μ indicate that the order of fractional order differential, Γ (x) are Gamma Function is defined asAnd Re (x) > 0.
Step 2-4-4) calculate error gradient.
Step 2-4-5) correct weights.Gradient according to error about weight, using classical stochastic gradient descent method amendment Network weight.Right value update mode is:
Wherein, i indicates that the network number of plies, η indicate learning rate, obtained by way of line search.
Step 2-5) k=k+1, go to step 2-4).
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto, Any one skilled in the art in the technical scope disclosed by the present invention, the change or replacement that can be readily occurred in, It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with scope of the claims Subject to.

Claims (7)

1. a kind of convolutional neural networks fractional order error back propagation method, it is characterised in that include the following steps:
Step 1) selects convolutional neural networks model;
Step 2) updates network weight using fractional order error back propagation method;
Step 3) obtains convolutional neural networks parameter according to the network weight.
2. convolutional neural networks fractional order error back propagation method according to claim 1, it is characterised in that the step It is rapid 1) to specifically include:
Step 1-1) neural network model is set, the neural network model includes one layer of input layer, n-layer hidden layer and one layer Output layer, the input layer, hidden layer, output layer node number correspond to n respectively1, n2, 1;
Step 1-2) a large amount of high-definition picture { X of settingiAnd its corresponding low-resolution image { YiComposition training set, In:X indicates that high-definition picture, Y indicate that low-resolution image, i indicate image index;
Step 1-3) it sets the weights of convolutional neural networks and is biased to Θ={ W, B }, set error function and activation primitive point Not Wei L and σ, wherein W indicate weights, B be biasing.
3. convolutional neural networks fractional order error back propagation method according to claim 1, it is characterised in that the step Rapid 2 include following sub-step:
Step 2-1) netinit:Initialize network weight and biasing Θ={ W1,B1, maximum iteration is set;
Step 2-2) input training data { Xi,Yi};
Step 2-3) setting primary iteration number k=1;
Step 2-4) network weight is optimized;
Step 2-5) according to k=k+1 update iterations, and jump to step 2-4).
4. convolutional neural networks fractional order error back propagation method according to claim 3, which is characterized in that
Step 2-4) it network weight is optimized specifically includes following steps:
Step 2-4-1) calculate network output valve;
Step 2-4-2) calculate error:Using the error function L, the error between network output valve and actual value is calculated, is sentenced Whether disconnected error meets the requirements, if met the requirements, network training terminates to be transferred to step 3);
If being unsatisfactory for requiring, modified weight is carried out, enters step 2-4-3);
Step 2-4-3) Fractional Derivative of activation primitive in error back propagation gradient is calculated, and calculate each neuron node Fractional Derivative;
Step 2-4-4) calculate error gradient;
Step 2-4-5) correct weights:Gradient according to error about weight, corrective networks weights.
5. convolutional neural networks fractional order error back propagation method according to claim 4, which is characterized in that the step Rapid 2-4-3) according to formula (1) calculate error back propagation gradient in activation primitive Fractional Derivative:
Wherein, GradlIndicate l layers of error back propagation gradient,For the input of activation primitive, i.e. network section The output of point,Indicate the of (l-1) layerA neuron is connected toThe weight of j-th of neuron of layer,It indicates The biasing of l layers of j-th of neuron, μ indicate that the order of Fractional Derivative, ⊙ are matrix corresponding position product, representing matrix Or point-to-point multiplying between vector;
The Fractional Derivative of each neuron node is calculated according to formula (2):
Wherein,For fractional order differential operator, D is 1 rank differential operator, and x indicates the output valve of neural network node, σ (x) tables Show that activation primitive, σ ' (x) indicate that 1 order derivative of activation primitive, μ indicate that the order of fractional order differential, Γ (x) are Gamma functions, It is defined asAnd Re (x) > 0.
6. convolutional neural networks fractional order error back propagation method according to claim 4, which is characterized in that step 2- Weights 4-5) are corrected according to formula (3) using classical stochastic gradient descent method,
Wherein, i indicates that the network number of plies, η indicate learning rate, obtained by way of line search,Indicate activation primitive Fractional Derivative.
7. according to claim 2 be based on convolutional neural networks fractional order error back propagation method, which is characterized in that step Rapid 1-3) in activation primitive σ expression formulas such as formula (4):
Wherein, x is network node output valve.
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Cited By (10)

* Cited by examiner, † Cited by third party
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CN109766993A (en) * 2018-12-13 2019-05-17 浙江大学 A kind of convolutional neural networks compression method of suitable hardware
CN111353534A (en) * 2020-02-27 2020-06-30 电子科技大学 Graph data category prediction method based on adaptive fractional order gradient
CN111382837A (en) * 2020-02-05 2020-07-07 鹏城实验室 Countermeasure sample generation method based on depth product quantization
CN111770437A (en) * 2020-06-09 2020-10-13 Oppo广东移动通信有限公司 Method and device for determining data card, terminal and storage medium
CN112200139A (en) * 2020-10-30 2021-01-08 杭州泰一指尚科技有限公司 User image identification method based on variable-order-fraction multilayer convolutional neural network
CN112597519A (en) * 2020-12-28 2021-04-02 杭州电子科技大学 Non-key decryption method based on convolutional neural network in OFDM (orthogonal frequency division multiplexing) encryption system
CN112766414A (en) * 2021-02-07 2021-05-07 辽宁大学 Image identification method based on Hausdorff-RMSprop algorithm
CN113392696A (en) * 2021-04-06 2021-09-14 四川大学 Intelligent court monitoring face recognition system and method based on fractional calculus
CN115878968A (en) * 2023-02-27 2023-03-31 山东交通学院 Signal noise reduction method based on extreme value characteristic neural network
CN111461229B (en) * 2020-04-01 2023-10-31 北京工业大学 Deep neural network optimization and image classification method based on target transfer and line search

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109766993A (en) * 2018-12-13 2019-05-17 浙江大学 A kind of convolutional neural networks compression method of suitable hardware
CN111382837B (en) * 2020-02-05 2023-07-18 鹏城实验室 Antagonistic sample generation method based on depth product quantization
CN111382837A (en) * 2020-02-05 2020-07-07 鹏城实验室 Countermeasure sample generation method based on depth product quantization
CN111353534A (en) * 2020-02-27 2020-06-30 电子科技大学 Graph data category prediction method based on adaptive fractional order gradient
CN111461229B (en) * 2020-04-01 2023-10-31 北京工业大学 Deep neural network optimization and image classification method based on target transfer and line search
CN111770437A (en) * 2020-06-09 2020-10-13 Oppo广东移动通信有限公司 Method and device for determining data card, terminal and storage medium
CN112200139A (en) * 2020-10-30 2021-01-08 杭州泰一指尚科技有限公司 User image identification method based on variable-order-fraction multilayer convolutional neural network
CN112200139B (en) * 2020-10-30 2022-05-03 杭州泰一指尚科技有限公司 User image identification method based on variable-order fractional multilayer convolutional neural network
CN112597519A (en) * 2020-12-28 2021-04-02 杭州电子科技大学 Non-key decryption method based on convolutional neural network in OFDM (orthogonal frequency division multiplexing) encryption system
CN112597519B (en) * 2020-12-28 2024-02-13 杭州电子科技大学 Non-key decryption method based on convolutional neural network in OFDM encryption system
CN112766414A (en) * 2021-02-07 2021-05-07 辽宁大学 Image identification method based on Hausdorff-RMSprop algorithm
CN113392696A (en) * 2021-04-06 2021-09-14 四川大学 Intelligent court monitoring face recognition system and method based on fractional calculus
CN115878968A (en) * 2023-02-27 2023-03-31 山东交通学院 Signal noise reduction method based on extreme value characteristic neural network

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Application publication date: 20181106