T-overlap query is the basis of set similarity query and has been applied in many important fields.Most existing approaches employ a pruning-and-verification framework,thus in low efficiency.Modern GPU has much higher...T-overlap query is the basis of set similarity query and has been applied in many important fields.Most existing approaches employ a pruning-and-verification framework,thus in low efficiency.Modern GPU has much higher parallelism as well as memory bandwidth than CPU and can be used to accelerate T-overlap query.In this paper,we use hash segmentation to divide inverted lists into segments,then design an efficient inverted index called GHSII on GPU using hash segmentation.Based on GHSII,a new segmentation parallel T-overlap algorithm,GSPS,is proposed.GSPS uses segment at a time to scan segments and uses shared memory to decrease the number of accesses to device memory.Furthermore,an optimized algorithm called GSPS-TLLO using a heuristic query order is proposed to solve the problem of load imbalance.Experiments are carried out on two real datasets and the results show that GSPS-TLLO outperforms the state-of-the-art GPU parallel T-overlap algorithms.展开更多
In marine engineering,appendages such as fin stabilizers and/or T-foils are made to rotate and to reduce the motion of ships.Research on the hydrodynamics of ships fitted with active appendages has significantly impro...In marine engineering,appendages such as fin stabilizers and/or T-foils are made to rotate and to reduce the motion of ships.Research on the hydrodynamics of ships fitted with active appendages has significantly improved the design and control of such ships.However,most studies focus on fixed rather than rotating appendages,thereby ignoring the hydrodynamic unsteadiness of active appendages.To enhance the reliability and precision of the numerical simulations,we propose the use of overlapping grids for simulating advanced catamarans fitted with a pair of rotating T-foils under each bow.The fundamental purpose of the overlapping grid technique is to realize information exchange via regional overlap sharing in each subdomain of the computing domain,instead of using the method of boundary sharing,thus greatly alleviating the difficulty of generating the subdomain grid;moreover,the technique guarantees the quality of the subdomain grid.Within the main computational domain,a subdomain was allocated to accommodate the T-foil.Overlapping meshes near the interface between the two domains enable information flow during the simulation;the overlapping grids are updated at every iteration step because the subdomain rotates.The instantaneous trim and sinkage responses of the catamaran to the T-foil rotation were reproduced.From the moment the active T-foil stopped moving,there was no change in the ship’s sailing attitude,indicating that the response was in real time.By comparing with EFD data,the numerical results showed reasonable agreement,indicating the feasibility and effectiveness of the technique in simulating the hydrodynamics of ships fitted with active appendages.展开更多
文摘T-overlap query is the basis of set similarity query and has been applied in many important fields.Most existing approaches employ a pruning-and-verification framework,thus in low efficiency.Modern GPU has much higher parallelism as well as memory bandwidth than CPU and can be used to accelerate T-overlap query.In this paper,we use hash segmentation to divide inverted lists into segments,then design an efficient inverted index called GHSII on GPU using hash segmentation.Based on GHSII,a new segmentation parallel T-overlap algorithm,GSPS,is proposed.GSPS uses segment at a time to scan segments and uses shared memory to decrease the number of accesses to device memory.Furthermore,an optimized algorithm called GSPS-TLLO using a heuristic query order is proposed to solve the problem of load imbalance.Experiments are carried out on two real datasets and the results show that GSPS-TLLO outperforms the state-of-the-art GPU parallel T-overlap algorithms.
基金Supported by the National Natural Science Foundation of China(Grant No.51509053)
文摘In marine engineering,appendages such as fin stabilizers and/or T-foils are made to rotate and to reduce the motion of ships.Research on the hydrodynamics of ships fitted with active appendages has significantly improved the design and control of such ships.However,most studies focus on fixed rather than rotating appendages,thereby ignoring the hydrodynamic unsteadiness of active appendages.To enhance the reliability and precision of the numerical simulations,we propose the use of overlapping grids for simulating advanced catamarans fitted with a pair of rotating T-foils under each bow.The fundamental purpose of the overlapping grid technique is to realize information exchange via regional overlap sharing in each subdomain of the computing domain,instead of using the method of boundary sharing,thus greatly alleviating the difficulty of generating the subdomain grid;moreover,the technique guarantees the quality of the subdomain grid.Within the main computational domain,a subdomain was allocated to accommodate the T-foil.Overlapping meshes near the interface between the two domains enable information flow during the simulation;the overlapping grids are updated at every iteration step because the subdomain rotates.The instantaneous trim and sinkage responses of the catamaran to the T-foil rotation were reproduced.From the moment the active T-foil stopped moving,there was no change in the ship’s sailing attitude,indicating that the response was in real time.By comparing with EFD data,the numerical results showed reasonable agreement,indicating the feasibility and effectiveness of the technique in simulating the hydrodynamics of ships fitted with active appendages.
