Category Archives: lecture

Revision Notes

Interrupts vs. Polling Pretty obvious stuff. Polling wastes resources. Polling is simple, requires no special hardware or CPU design. Interrupts are synchronous; CPU can go off and do something else. Interrupts are more complicated, more difficult to implement. Ada Interrupts … Continue reading

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Distributional Clustering

We’re going to look at: Distributional Similarity Clustering (Hierarchical and flat) Distributional Hypothesis states that words that occur in the same contexts tend to have similar meanings. Two words are similar to the extent that they share similar contexts. But … Continue reading

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WotrdNets and Lexical Relations

What is lexical semantics? It is the study of the meaning of words, and how these combine to form the meaning of longer contexts (paragraphs, etc.). Words and concepts are a many-to-many relation. This results in lexical ambiguity; one phrase … Continue reading

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Compositional Semantics

Sort of recap: S -> NP VP S' -> VP'(NP') Today looking at quantified expressions; expressions with quantifiers such as ‘Everyone’. ‘Everyone sleeps’, where ‘everyone’ is the set of people, you would represent it as: S' = forall x (person'(x) … Continue reading

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Revision Notes

Parsers Chart parsers are better than backtracking parsers because they are more efficient. This is because in a backtracking parser partial successful parses are thrown away, and so have to be parsed again. A chart parser maintains all sub-parses. Active … Continue reading

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Worst Case Execution Time (and more)

Worst-case execution time is C values in all the equations we use. Known as ‘Timing Analysis’. You either use static analysis or measurement. Static analysis is pessimistic whereas measurement is potentially optimistic (makes sense intuitively). Without semantic meaning you might … Continue reading

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Phrasal Categories and Subcategorisation

Previously we were talking about control verbs, e.g. ‘promise’ and ‘persuade’. These have different ‘controllers’. E.g. Sandy persuaded Kim to come home early. The VP ‘to come home early’ is related to Kim, but. Sandy promised Kim to come home … Continue reading

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More Scheduling

Extensions on Task Model Release Jitter: Arbitrary Deadlines: Where the deadline is greater than the period. Cooperative Scheduling: True preemptive behaviour is not always acceptable for safety-critical systems. But pure non-preemptive reduces schedulability. Cooperative scheduling is a compromise. Blocks of … Continue reading

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Scheduling Real-Time Systems

Scheduling In general, a scheduling scheme provides 2 features: An algorithm for ordering the use of system resources A means for predicting worst-case behaviour when the algorithm is applied. Cyclic Executives Most hard real-time systems use a cyclic executive, though … Continue reading

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Revision Notes

Public-key cryptography Keys can come in pairs; an encryption key and a decryption key. Can’t generate one key from the other. Knapsack Algorithms Knapsack algorithms came first. Based off the knapsack problem, an NP-complete problem: Given a pile of items … Continue reading

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