According to an embodiment, a lattice finalization device finalizes a portion of a lattice that is generated by pattern recognition with respect to a signal on a frame-by-frame basis in chronological order. The device includes a detector and a finalizer. The detector is configured to detect, as a splitting position, a frame in the lattice in which the number of nodes and passing arcs is equal to or smaller than a reference value set in advance. The finalizer is configured to finalize nodes and arcs in paths from a start node to the splitting position in the lattice.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A lattice finalization device that finalizes a portion of a lattice that is generated by pattern recognition with respect to a signal on a frame-by-frame basis in chronological order, the device comprising: a detector configured to detect, as a splitting position, a frame in the lattice in which the number of nodes and passing arcs is equal to or smaller than a reference value set in advance; and a finalizer configured to finalize nodes and arcs in paths from a start node to the splitting position in the lattice. 2. The device according to claim 1, further comprising a selector configured to select, from among nodes at the splitting position or arcs passing through the splitting position, at least a single node or a single arc as a residual element, wherein when the residual element is a node, the finalizer finalizes nodes and arcs in a plurality of paths from the start node to the residual element, and when the residual element is an arc, the finalizer finalizes nodes and arcs in a plurality of paths from the start node either to immediately preceding node to the residual element or to immediately following node to the residual element. 3. The device according to claim 2, wherein the selector selects, as the residual element, one of the nodes at the splitting position or one of the arcs passing through the splitting position. 4. The device according to claim 2, wherein the selector detects, from among a plurality of paths from the start node to an end node in the lattice, at least a single path in sequence starting from path having best score that represents degree of coincidence with signals, and selects, as the residual element, a node at the splitting position or an arc passing through the splitting position in the at least single detected path. 5. The device according to claim 2, wherein the selector detects, from among a plurality of paths from the start node to the splitting position in the lattice, at least a single path in sequence starting from path having best score that represents degree of coincidence with signals, and selects, as the residual element, a node at the splitting position or an arc passing through the splitting position in the at least single detected path. 6. The device according to claim 2, wherein the selector detects, from among a plurality of paths from the start node to a specified frame from among frames between the splitting position and an end node in the lattice, at least a single path in sequence starting from path having best score that represents degree of coincidence with signals, and selects, as the residual element, a node at the splitting position or an arc passing through the splitting position in the at least single detected path. 7. The device according to claim 2, wherein the selector detects, from among nodes at the splitting position or arcs passing through the splitting position, a single node or a single arc in descending order of paths having most number of branches up to the one or more end nodes, and selects, as the residual element, the single detected node or arc. 8. The device according to claim 1, wherein, from the start node to an end node, when there is more than one frame in which the number of nodes and passing arcs is equal to or smaller than the reference value, the detector detects, as the splitting position, most temporally posterior frame. 9. The device according to claim 1, wherein the detector detects, as the splitting position, a frame positioned after a predetermined number of frames from the start node. 10. The device according to claim 2, further comprising a deleter configured to, from the lattice, delete a node and a passing arc at the splitting position which do not represent the residual element and delete a node and an arc which are not able to reach the residual element in temporally anterior frames to the splitting position. 11. The device according to claim 2, further comprising a deleter configured to, from the lattice, delete a node and a passing arc at the splitting position which do not represent the residual element and delete a node and an arc which are not able to arrive from the residual element in temporally posterior frames to the splitting position. 12. The device according to claim 1, further comprising a timing controller configured to determine a timing for performing an operation of finalizing a portion of the lattice, wherein while pattern recognition is underway, the timing controller ensures that an operation of finalizing a portion of the lattice is performed. 13. The device according to claim 12, wherein, the timing controller ensures that an operation of finalizing a portion of the lattice is performed at time of performing a pruning operation during pattern recognition. 14. The device according to claim 1, wherein the finalizer separates finalized nodes and arcs into a new lattice isolated from un-finalized nodes and arcs, and newly registers a start node in the lattice that is not finalized. 15. The device according to claim 14, wherein the finalizer outputs the new lattice that is separated and deletes the new lattice after output thereof. 16. The device according to claim 1, wherein in the lattice, all arcs represent transition between nodes of two successive frames, and the detector detects, as the splitting position, a single frame in which the number of nodes is equal to or smaller than the reference value. 17. The device according to claim 1, wherein the lattice includes arcs representing transition between nodes of two frames over a wider range than two successive frames, and the detector detects, as the splitting position, a single frame in which a total of the number of nodes and the number of passing arcs is equal to or smaller than the reference value. 18. A pattern recognition device comprising: a decoder configured to generate a lattice by pattern recognition with respect to a signal on a frame-by-frame basis in chronological order; and the lattice finalization device according to claim 1 to finalize a portion of the lattice generated by the decoder. 19. A lattice finalization method for finalizing a portion of a lattice that is generated by pattern recognition with respect to a signal on a frame-by-frame basis in chronological order, the method comprising: detecting, as a splitting position, a frame in the lattice in which the number of nodes and passing arcs is equal to or smaller than a reference value set in advance; and finalizing nodes and arcs in paths from a start node to the splitting position in the lattice. 20. A computer program product comprising a computer-readable medium containing a program executed by a computer for finalizing a portion of a lattice that is generated by pattern recognition with respect to a signal on a frame-by-frame basis in chronological order, the program causing the computer to execute: detecting, as a splitting position, a frame in the lattice in which the number of nodes and passing arcs is equal to or smaller than a reference value set in advance; and finalizing nodes and arcs in paths from a start node to the splitting position in the lattice.