In implementations of the subject matter described herein, a machine learning scheme is proposed. Features of historical inputs from a user as well as corresponding outputs presented to the user in response to the historical inputs are obtained, where the features are previously determined based on contexts of the historical inputs which indicate information related to the user. The features of the historical inputs are assigned into a plurality of groups. An association is determined on the basis of the plurality of groups of features. Specifically, an association indicating inter-group correlations of features from different ones of the groups is determined according to the obtained outputs. Therefore, in determining the association, intra-group correlations such as correlations of features within a group are excluded. In this way, the time and computation complexity for the association determination will be effectively reduced.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A device comprising: a processing unit; a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, performing acts including: obtaining features of historical inputs from a user and corresponding outputs presented to the user in response to the historical inputs, the features being determined based on contexts of the historical inputs, the contexts indicating information related to the user; assigning the features of the historical inputs into a plurality of groups; and determining, based on the outputs, an association at least indicating inter-group correlations of features from different ones of the groups. 2. The device of claim 1, wherein the determining comprises: determining a first inter-group correlation of features selected from a first number of the groups and a second inter-group correlation of features from a second number of the groups, the second number being different from the first number. 3. The device of claim 2, wherein the first number is less than the second number, and the acts further include: extending a dimension of the first inter-group correlation by adding dummy features to the second number of the groups according to the second number. 4. The device of claim 3, wherein the determining comprises: factorizing the extended first inter-group correlation and the second inter-group correlation to obtain a plurality of factors; and determining, based on the outputs, the plurality of factors as the first and second inter-group correlations. 5. The device of claim 2, wherein the association further indicates a factor related to at least one of a bias value or weights for the features, and the acts further include: extending a dimension of the factor by adding dummy features to the second number of the groups according to the second number. 6. The device of claim 1, wherein determining the association comprises: generating a super-group based on a first group and a second group from the plurality of groups; and determining the inter-group correlation of features within the super-group. 7. The device of claim 6, wherein determining the association further comprises: generating a further super-group based on the first group and a third group from the plurality of groups; and determining the inter-group correlation of features within the further super-group. 8. The device of claim 1, wherein the assigning comprises: assigning a first feature of the features into at least two of the groups. 9. The device of claim 1, wherein the determined association is stored in a storage device. 10. A device comprising: a processing unit; a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, performing acts including: in response to receiving an input from a user, determining a context of the input, the context indicating information related to the user; obtaining a plurality of features based on the context; assigning the features into a plurality of groups; and generating an output based on the plurality of groups of features according to a predefined association at least indicating inter-group correlations of features from different ones of the groups. 11. The device of claim 10, wherein the association indicates a first inter-group correlation of features selected from a first number of the groups and a second inter-group correlation of features from a second number of the groups, the first number is less than the second number; and wherein the generating comprises: modifying the plurality of groups by adding dummy features to the second number of the groups based on the second number; and generating the output based on the modified groups according to the association. 12. The device of claim 10, wherein the association further indicates a factor related to at least one of a bias value or weights for the features. 13. A computer-implemented method comprising: obtaining features of historical inputs from a user and corresponding outputs presented to the user in response to the historical inputs, the features being determined based on contexts of the historical inputs, the contexts indicating information related to the user; assigning the features of the historical inputs into a plurality of groups; and determining, based on the outputs, an association at least indicating inter-group correlations of features from different ones of the groups. 14. The method of claim 13, wherein the determining comprises: determining a first inter-group correlation of features selected from a first number of the groups and a second inter-group correlation of features from a second number of the groups, the second number being different from the first number. 15. The method of claim 14, wherein the first number is less than the second number, and the acts further include: extending a dimension of the first inter-group correlation by adding dummy features to the second number of the groups according to the second number. 16. The method of claim 15, wherein the determining comprises: factorizing the extended first inter-group correlation and the second inter-group correlation to obtain a plurality of factors; and determining, based on the outputs, the plurality of factors as the first and second inter-group correlations. 17. The method of claim 14, wherein the association further indicates a factor related to at least one of weights for the features or a bias value, and the acts further include: extending a dimension of the factor by adding dummy features to the second number of the groups according to the second number. 18. The method of claim 13, wherein determining the association comprises: generating a super-group based on a first group and a second group from the plurality of groups; and determining the inter-group correlation of features within the super-group. 19. The method of claim 18, wherein determining the association further comprises: generating a further super-group based on the first group and a third group from the plurality of groups; and determining the inter-group correlation of features within the further super-group. 20. The method of claim 13, wherein the assigning comprises: assigning a first feature of the features into at least two of the groups.