Embodiments relate to performing an ensemble model based prediction for a set of input data records. An aspect includes creating an assignment table assigning all data records in the input data set to a root node of a tree. Another aspect includes splitting the assignment tables into disjoint sub-tables. Another aspect includes storing each of the sub-tables to a respective data slice. Another aspect includes designating root nodes of each of the plurality of trees as a set of current nodes. Another aspect includes evaluating split conditions of each identified current node based on data records that are assigned to the current node; re-assigning said input data records to one or more child-nodes; using the child nodes of all current nodes as the set of current nodes; and calculating a prediction result from the assignment of data records to the leaf nodes of each of a plurality of trees.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A computer implemented method for performing an ensemble model based prediction for a set of input data records, the ensemble model comprising a plurality of trees comprising decision trees or regression trees, the method comprising: creating, for each of the trees in the ensemble model, an assignment table, each assignment table assigning all data records in the input data set to a root node of said tree, in a database management system that is in control of a plurality of processing units and of a plurality of data slices, the database management system being operable to process data stored in any one of the data slices by a respective one of the processing units; splitting each of the assignment tables into disjoint sub-tables; storing each of the sub-tables to a respective one of the data slices; designating root nodes of each of the plurality of trees as a set of current nodes corresponding to a current level of all the trees; executing in parallel until all of the assignment tables are assigned to leaf nodes of the plurality of trees, by all processing units whose respective data slice comprises one or more of the sub-tables: performing a single pass through the sub-tables stored in the data slice of said processing unit, thereby identifying one or more of the current nodes having been assigned to one or more of the data records of said data slice; evaluating split conditions of each of the identified current nodes on the data records assigned to said current node; based on said evaluation, de-assigning input data records from each of said current nodes and re-assigning said input data records to one or more of the child-nodes of said current node; using the child nodes of all current nodes as the set of current nodes corresponding to the current level of each of the plurality of trees; and calculating a prediction result from the assignment of data records to the leaf nodes of each of the plurality of trees. 2. The computer-implemented method of claim 1, wherein each one of the assignment tables comprises data record identifiers and associated pointers, wherein the data record identifiers of each assignment table consist of the identifiers of all input data records of the input data set and each one of the associated pointers points to one of the one or more current nodes of one of the trees, wherein each of the pointers associated with one of the identifiers assigns the data record of said identifier to the current node referred to by the pointer. 3. The computer-implemented method of claim 1, wherein each of the disjoint sub-tables comprises disjoint sub-sets of the data record identifiers of the set of input data records. 4. The computer-implemented method of claim 1, further comprising transferring, by the database management system, the sub-tables to the data slices and storing them into said data slices via a network connection. 5. The computer-implemented method of claim 1, further comprising: storing all sub-tables derived from the same one of the assignment tables in different ones of the data slices, wherein the de-assigning input data records comprises updating the assignment of data records and current nodes contained in each of the sub-tables derived from the same one of the assignment tables in parallel. 6. The computer-implemented method of claim 1, wherein identifying of the one or more of the current nodes having assigned one or more of the data records in the data slices is implemented by evaluating in parallel, by the processing units of the respective data slices, the sub-tables stored in said data slices. 7. The computer implemented method of claim 1, wherein calculating the prediction result comprises: for each of the plurality of trees, calculating a tree-specific prediction as a derivative of the assignment of input data records to the leaf nodes of said tree; and calculating a final prediction result from the tree-specific predictions. 8. The computer-implemented method of claim 7, wherein the leaf nodes of the trees have assigned class labels or class probability distributions, wherein the plurality of trees are decision trees, and wherein calculating the tree-specific predictions comprises: assigning the class labels of the leaf nodes to all input data records assigned to said leaf nodes; and wherein calculating the final prediction result comprises, for each of the data records of the input data set: identifying one leaf node in each of the trees to which said data record is assigned according to the assignment tables; calculating, from all class labels or all class probability distributions of the identified leaf nodes a predicted class, the predicted class being is one out of a plurality of predefined classes, the predicted class being calculated to comprise said data record with a higher probability than any one of the other predefined classes; and assigning a class label of the predicted class to said input data record; wherein the assignment of all input data records of the input data set to their respectively calculated class labels is returned as the final prediction result. 9. The computer-implemented method of claim 8, wherein the leaf nodes of the trees have assigned numeric target attribute values, wherein the trees are regression trees, wherein calculating the tree-specific predictions comprises: assigning the numeric target attribute values of the leaf nodes to all input data records assigned to said leaf nodes; and wherein calculating the final prediction result comprises, for each of the data records of the input data set: identifying one leaf node in each of the trees to which said data record is assigned according to the assignment tables; calculating a derivative attribute value from the numeric target attribute values of all identified leaf nodes; and assigning the derivative attribute value to said data record of the input data set; wherein the assignment of all input data records of the input data set to their respectively calculated derivative attribute values is returned as the final prediction result. 10. A computer program product for performing an ensemble model based prediction for a set of input data records, the ensemble model comprising a plurality of trees comprising decision trees or regression trees, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processing circuit to cause the processing circuit to: create, for each of the trees in the ensemble model, an assignment table, each assignment table assigning all data records in the input data set to a root node of said tree, in a database management system that is in control of a plurality of processing units and of a plurality of data slices, the database management system being operable to process data stored in any one of the data slices by a respective one of the processing units; split each of the assignment tables into disjoint sub-tables; store each of the sub-tables to a respective one of the data slices; designate root nodes of each of the plurality of trees as a set of current nodes corresponding to a current level of all the trees; execute in parallel until all of the assignment tables are assigned to leaf nodes of the plurality of trees, by all processing units whose respective data slice comprises one or more of the sub-tables: performing a single pass through the sub-tables stored in the data slice of said processing unit, thereby identifying one or more of the current nodes having been assigned to one or more of the data records of said data slice; evaluating split conditions of each of the identified current nodes on the data records assigned to said current node; based on said evaluation, de-assigning input data records from each of said current nodes and re-assigning said input data records to one or more of the child-nodes of said current node; using the child nodes of all current nodes as the set of current nodes corresponding to the current level of each of the plurality of trees; and calculating a prediction result from the assignment of data records to the leaf nodes of each of the plurality of trees. 11. The computer program product of claim 10, wherein each one of the assignment tables comprises data record identifiers and associated pointers, wherein the data record identifiers of each assignment table consist of the identifiers of all input data records of the input data set and each one of the associated pointers points to one of the one or more current nodes of one of the trees, wherein each of the pointers associated with one of the identifiers assigns the data record of said identifier to the current node referred to by the pointer. 12. The computer program product of claim 10, wherein each of the disjoint sub-tables comprises disjoint sub-sets of the data record identifiers of the set of input data records. 13. The computer program product of claim 10, further comprising transferring, by the database management system, the sub-tables to the data slices and storing them into said data slices via a network connection. 14. The computer program product of claim 10, further comprising: storing all sub-tables derived from the same one of the assignment tables in different ones of the data slices, wherein the de-assigning input data records comprises updating the assignment of data records and current nodes contained in each of the sub-tables derived from the same one of the assignment tables in parallel. 15. The computer program product of claim 10, wherein identifying of the one or more of the current nodes having assigned one or more of the data records in the data slices is implemented by evaluating in parallel, by the processing units of the respective data slices, the sub-tables stored in said data slices. 16. A computer system for performing an ensemble model based prediction for a set of input data records, the ensemble model comprising a plurality of trees comprising decision trees or regression trees, the system comprising: a memory; and a processor, communicatively coupled to said memory, the computer system configured to perform a method comprising: creating, for each of the trees in the ensemble model, an assignment table, each assignment table assigning all data records in the input data set to a root node of said tree, in a database management system that is in control of a plurality of processing units and of a plurality of data slices, the database management system being operable to process data stored in any one of the data slices by a respective one of the processing units; splitting each of the assignment tables into disjoint sub-tables; storing each of the sub-tables to a respective one of the data slices; designating root nodes of each of the plurality of trees as a set of current nodes corresponding to a current level of all the trees; executing in parallel until all of the assignment tables are assigned to leaf nodes of the plurality of trees, by all processing units whose respective data slice comprises one or more of the sub-tables: performing a single pass through the sub-tables stored in the data slice of said processing unit, thereby identifying one or more of the current nodes having been assigned to one or more of the data records of said data slice; evaluating split conditions of each of the identified current nodes on the data records assigned to said current node; based on said evaluation, de-assigning input data records from each of said current nodes and re-assigning said input data records to one or more of the child-nodes of said current node; using the child nodes of all current nodes as the set of current nodes corresponding to the current level of each of the plurality of trees; and calculating a prediction result from the assignment of data records to the leaf nodes of each of the plurality of trees. 17. The system of claim 16, wherein each one of the assignment tables comprises data record identifiers and associated pointers, wherein the data record identifiers of each assignment table consist of the identifiers of all input data records of the input data set and each one of the associated pointers points to one of the one or more current nodes of one of the trees, wherein each of the pointers associated with one of the identifiers assigns the data record of said identifier to the current node referred to by the pointer. 18. The system of claim 16, wherein each of the disjoint sub-tables comprises disjoint sub-sets of the data record identifiers of the set of input data records. 19. The system of claim 16, further comprising transferring, by the database management system, the sub-tables to the data slices and storing them into said data slices via a network connection. 20. The system of claim 16, further comprising: storing all sub-tables derived from the same one of the assignment tables in different ones of the data slices, wherein the de-assigning input data records comprises updating the assignment of data records and current nodes contained in each of the sub-tables derived from the same one of the assignment tables in parallel.