Abstract
Intelligent city is a product of the deep integration of information technology, industrialization and urbanization, which has a large number of intelligent mechanical products. The users widely evaluate their application characteristics, and the selection of mechanical products based on user evaluation has become a trend. Nowadays, personalized mechanical product recommendation based on user evaluation is more and more widely used. However, due to the sparse evaluation data, the recommendation accuracy needs to be improved. In this paper, the principle of matrix decomposition is deeply analyzed in order to provide useful ideas for solving this problem. The bias weight hybrid recommendation model of user preference and rating object characteristics is proposed, and the corresponding hybrid recommendation algorithm is designed. First, estimated data obtained using the matrix decomposition principle is supplemented to the sparse data matrix. Secondly, according to the characteristics of users and ratings, initial positions were set based on the statistical distribution of high-performance computing data, and bias weights were set by incorporating each feature. Finally, the nonlinear learning ability of deep neural network learning is used to enhance the classification effectiveness. Practice has proved that the constructed model is reasonable, the designed algorithm converges fast, the recommendation accuracy is improved by about 10%, and the model better alleviates the problem of sparse scoring data. The practical application is simple and convenient, and has good application value.
Keywords
Introduction
The Internet and the application systems running on it have generated massive data online. In the design [1] and evaluation of mechanical products [2], the recommendation based on multidimensional evaluation has become the mainstream personalized recommendation method [3], and greatly improved the recommendation. Personalized recommendation is the ability to accurately identify the characteristics of the user’s needs for the product usage, and to select the suitable product for them in a targeted manner [4]. Users evaluate the subjective satisfaction of products to create a scoring matrix, and collaborative filtering is conducted based on the correlation between rows and columns. It has been applied to personalized recommendation in many industries. The richer the data, the more accurate the recommendation. Kabbur et al. [5] solved the problem of sparse similarity matrix between items by decomposing the similarity matrix into the product of two low-rank matrices. Sarwar et al. [6] analyzed the item-based prediction methods and proposed a new item similarity model for improving the effectiveness of recommendation. Common collaborative filtering has no absolute advantage. Different application scenarios have different recommendation effects [7]. Since the initial data will have a cold start problem, there will be a Matthew effect [8]. Due to various objective reasons, the score set always has sparsity, and the coverage rate is very low, which affects the recommendation accuracy. The ideal goal of recommendation quality and effect cannot be achieved.
The new generation of intelligent computing technology represented by deep learning will be further applied to the optimized design, quality evaluation, and use recommendation of mechanical products. By utilizing distributed computing, sparse computing, and GPU acceleration, deep neural networks can parallelly process large-scale data and computing tasks, effectively achieving high-performance computing. It can obtain hidden, valid and understandable knowledge from huge amount of data. By expressing, modeling and quantifying the features of various personalized needs, and then substituting these data into deep learning networks for training and searching, and finally outputting personalized results automatically, this is the process of deep learning networks in personalized recommendation [9]. Nonlinear learning ability of deep learning technology can bring opportunities to solve problems [10] such as sparse data. Better results have been achieved in complex model design [11], state identification [12], performance optimization [13], metrics evaluation [14], and personalized recommendation [15]. Deep learning can use infinite approximation of an arbitrary continuous function to learn the nonlinear feature representations between the user and the item. Deep neural networks are utilized instead of the dot product operation in traditional linear relationships to capture feature representations between users and items, and can also be combined with other recommendation models. Analyze the correlation of evaluation and fuse the feature preference [16], use implicit characteristics information as a supplement to explicit characteristics [17], and the effective combination of them alleviates the inaccurate information. The fusion of preference characteristics, the fast placement in the initial position to accelerate convergence and the deep learning technology will solve the problem of the sparse evaluation data and effectively improve the recommendation speed and accuracy, which will be an effective hybrid recommendation method.
The main contributions are as follows:
Aiming at the problems such as sparse rating data, lack of personalized factors, and random initial data in traditional mechanical product personalized recommendation, using matrix analysis principles and deep learning technology, a hybrid recommendation model is proposed based on user preferences and characteristics of the rating object. Based on the statistical distribution of data obtained from high-performance computing, the initial position is set, and weights are set by merging each feature. An intelligent recommendation algorithm is designed using deep neural network technology. Practice has proven that the constructed model is reasonable, the designed algorithm has a fast convergence speed, and the recommendation accuracy has been improved by about 10%, effectively alleviating the problem of sparse rating data.
Traditional recommendation models mainly include content recommendation, collaborative filtering, matrix decomposition, logistic regression, deep learning, etc., which have their own characteristics, as shown in Table 1.
Recommendation models’ characteristics
Recommendation models’ characteristics
According to the principle of nonnegative matrix factorization, for a given nonnegative matrix A, a nonnegative matrix U and a nonnegative matrix V can be found. Thus, a nonnegative matrix is decomposed into the product of two nonnegative matrices. Given any nonnegative matrix
In the construction of intelligent cities, intelligent mechanical products have different application characteristics, and users will evaluate each feature and generate an evaluation matrix A. The element
Because of its simplicity, interpretability, less storage and other obvious characteristics, it can be used to reduce the matrix dimension describing the problem, and can also compress and summarize a large amount of data. Nonnegative matrix factorization is an NP problem. Since the product of
The optimization objective is to find the minimum value of SSE, and transform it into a machine learning problem.
The gradient descent method can be used to solve
Iterate and update until
To prevent over fitting, regularization term can be added, then:
Also use the gradient descent method to solve.
Update according to the direction of the negative gradient.
Iterate and update until convergence.
Due to the different preferences of individual users and the different characteristics of items, the scoring results are different. Different weight conditions can be set according to the bias of various characteristics, such as the average score, user rating tendency, item rating tendency and other characteristic factors.
Some bias conditions have time characteristics, so the time factor should be considered, then:
In order to improve the convergence direction, the initial value of the score is quickly set to the average position by using the statistical characteristics of the score. Then randomly initialize the average value to accelerate convergence.
Therefore, combining the characteristics of all parties and improving the fast convergence of the model, a comprehensive recommendation of offset weight fast setting hybrid recommendation is formed, which has better recommendation performance and effect.
According to the bias weight fast position estimation, complete the score matrix vacancy and input into the convolution neural network (CNN). After classification training, personalized recommendation can be made.
Set the number of hidden features KH, the number of iterations D, the threshold E, initialize the user matrix W and the feature matrix V. Within the number of iterations D, unrated, repeat step (3)–(5); Compute Update ( For the scored, calculate Calculate the product A of W and V, get the score matrix A. Set the A attribute column and the classification label column, and set the training set XA and the test set XB according to the ratio. Input XA and XB into the designed CNN network, and output classification set AA, then make the classified recommendation.
The recommendation algorithm has the following characteristics.
The generalization ability is strong, which can solve the problem of sparse matrix to a certain extent. The space complexity is low. The algorithm complexity is Good flexibility and expansibility. To solve matrix vectors
Bias weight recommendation
Six users rated 8 items on a 5-point scale after using them. The value of no rating is 0. Get the data set A
Parameter setting: iteration number D
The convergence of the improve model.
The scoring matrix of result 2.
Convergence of fast setting model.
Get the scoring matrix in Fig. 2. The unrated items have been completely filled, and personalized recommendation can be realized.
In order to speed up the convergence speed, W and V are quickly positioned to a reasonable position at the beginning, which is improved to a fast position recommendation model.
Count score set. According to the average user score and the average item evaluation score, respectively they are:
W0
CNN structure diagram
CNN structure diagram
CNN training progress.
Classification accuracy.
Initialize it as a 5-point scoring matrix according to the average value. Fast recommendation can be achieved by iteratively generating W and V according to section 5.1. The convergence results are shown in Fig. 3. Result3 is the convergence of the improved fast setting recommendation, which quickly drops to the convergence direction and reduces the error by 70%.
The dataset contains 357 rating samples with incomplete ratings (0 means unrated item). Each sample has 12 rating items and 1 recommended classification mark (4 categories). Based on section 5.1 and section 5.2, a complete scoring set is obtained, and a 12-layer CNN deep neural network is designed. As shown in Table 2, use the SGDM gradient descent method, the maximum number of training is 1000, the initial learning rate is 0.001 and learning rate decline factor is 0.1. After 450 training sessions, the learning rate was 0.001 * 0.1. The training is shown in Fig. 4.
The problem of data sparseness is solved to some extent by using offset weight fast position hybrid recommendation, and the recommendation accuracy is improved from 87.5% to 95.83%, as shown in Fig. 5.
Conclusion and future perspective
Aiming at the problems of sparse scoring data, lack of personalized factors and random initial data in traditional personalized recommendation of mechanical products, the characteristics of user scoring and resource scoring tendency are analyzed. According to the principle of matrix decomposition, user rating tendency, product rating tendency and other characteristic factors, different weight bias conditions are established. Based on the statistical characteristics of the score, the score value is quickly set to the position near the average value to accelerate the convergence. Based on the nonlinear learning ability of deep neural network, a hybrid recommendation method of bias weight fast setting is proposed. Compared with similar algorithms, the problem of data sparsity has been solved. the recommendation accuracy has improved by about 10% in the hybrid recommendation method. The recommendation accuracy is improved from 87.5% to 95.83%. The algorithm complexity is
In the face of massive data in network application systems, properly combining deep learning technology and improving parallel computing will further improve the recommendation speed and accuracy, and will have better application prospects.
With the widespread application of mechanical products, the increase in application characteristics, the increase in data dimensions, and the imbalance of data will all affect the recommendation effect. At the same time, with the continuous increase in massive data, the calculation speed will be affected. Methods such as dimensionality reduction and parallel computing are used to solve these problems, and achieve high-performance computing goals. The next step is to continue to study the following: 1) Comprehensive analysis of multidimensional data. In future research, comprehensive analysis of data of different dimensions will be carried out, for example, relevant features between project data will be used to extract user preferences. The processing of data imbalance will also bring an undeniable impact on the application effect. The solution is that multiple dimensions of state information should be effectively integrated to improve the generalization and stability of the recognition model based on deep learning technology, to train a more effective state recognition model, and to establish a better deep learning state recognition model system. 2) Reasonable consideration of the impact of multiple auxiliary factors. Since the user-item interaction is related to many auxiliary factors, different auxiliary information for an item has different impacts on the user’s preference. In the future the possible methods need to consider the impacts of multiple auxiliary information on the model’s performance to further optimize the existing model.
Footnotes
Conflict of interest
The author declared no potential conflicts of interest with respect to the research, author-ship, and/or publication of this article.
Data availability
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
