Abstract: Memory may be managed by a garbage collector. The memory may contain a data structure and an index. The data structure may include a plurality of objects. The index may index a plurality of the objects in the data structure. For each object which it indexes, the index may contain a key field and a weak reference to the object. The key field may be indicative of an attribute of the object. The weak reference to the object may be associated with the key field. The weak reference may have a configuration which is not followed by a pointer tracer of the garbage collector when the garbage collector seeks to determine which of the objects in the data structure are no longer reachable from outside of the data structure during a memory reclamation process. This may insure that the index does not prevent the memory occupied by any unreachable object in the data structure from being reclaimed by the garbage collector during the memory reclamation process, even though the object is still referenced by the index.

Abstract: Techniques for language instruction and teaching are described. Methods focus on the sound distinctions that learners have trouble discriminating. Learners practice discriminating these sounds. A learning system is developed using databases of speech from people discriminating these sounds. An embodiment of a method according to the present disclosure can utilize sets of words that differ by only a single syllable containing a sound that is difficult to pronounce, as a way to teach the pronunciation of a word. The sets of similar words can be of a desired number or have a desired number of constituent members. Embodiments of systems can include user interfaces and a automated speech recognition system, including suitable automated speech recognition software, that can interact with a user, e.g., in a pedagogical setting. Related software products including computer-readable instructions resident in a computer-readable medium are described. HMM and DTW algorithms may be used for the embodiments.