Consider a system running 10 i/o-bound processes and 1 cpu-bound process. assume that the i/o- bound processes issue an i/o operation once for every millisecond of cpu computing and that each i/o operation takes 10 milliseconds to complete (we assume that there is no competition among i/o operations). assume that the cpu-bound processes do not issue any i/o operations. a round-robin scheduler with quantum size 1 milliseconds is used to schedule all these 11 processes together. we assume that the context-switching overhead is 0.1 millisecond and that all processes are long-running tasks. calculate the cpu utilization.

Some of your friends have gotten into the burgeoning field of time-series data mining, in which one looks for patterns in sequences of events that occur over time. purchases at stock exchanges"what's being bought" are one source of data with a natural ordering in time. given a long sequence s of such events, your friends want an efficient way to detect certain "patterns" in them"for example, they may want to know if the four events buy yahoo, buy ebay, buy yahoo, buy oracle occur in this sequence s, in order but not necessarily consecutively. they begin with a collection of possible events (e.g., the possible transactions) and a sequence s of n of these events. a given event may occur multiple times in s (e.g., yahoo stock may be bought many times in a single sequence s). we will say that a sequence s is a subsequence of s if there is a way to delete certain of the events from s so that the remaining events, in order, are equal to the sequence s . so, for example, the sequence of four events above is a subsequence of the sequence buy amazon, buy yahoo, buy ebay, buy yahoo, buy yahoo, buy oracle their goal is to be able to dream up short sequences and quickly detect whether they are subsequences of s. so this is the problem they pose to you: give an algorithm that takes two sequences of events"s of length m and s of length n, each possibly containing an event more than once"and decides in time o(m + n) whether s is a subsequence of s.

Ap practice - performance task response the ap create performance task asks you to write about an abstraction that you developed and wrote into your code. most of the time that means identifying a function or procedure you wrote to "manage complexity" in your program. here is the actual prompt from the create performance task: 2d. capture and paste a program code segment that contains an abstraction you developed individually on your own (marked with a rectangle). this abstraction must integrate mathematical and logical concepts. explain how your abstraction manage the complexity of your program. (must not exceed 200 words) below is a segment of code from an "under the sea" program with a rectangle drawn around a portion of the code identifying an abstraction. imagine that you wrote this and are composing an ap response about how this abstraction manages complexity. (note: ignore the requirement that the abstraction integrate "mathematical and logical concepts" for this practice response. just write about managing complexity). explain how the abstraction marked with the rectangle in the code above manage complexity of this program. write your response here submit

Consider a slotted aloha system, where the time slot equals the fixed duration of each packet. assume that there are 4 stations a,b,c,d sharing the medium. (a) stations a,b,c,d receive one packet each from higher layers at times 1.3, 1.5, 2.6,5.7 respectively. show which transmissions take place when, according to the slottedaloha protocol; describe all transmissions until all four packets have been successful.when needed, each station has access to the following sequence of random number, provided by a random number generator and drawn uniformly between 0 and 1: (1) station a draws numbers: 0.31, 0.27, 0.78, 0.9, 0.9, 0.11, 0. (2) station b draws numbers: 0.45, 0.28, 0.11, 0.83, 0.37, 0.22, 0. (3)station c draws numbers: 0.1, 0.2, 0.3, 0.4, 0. (4) station d draws numbers: 0.36, 0.77, 0.9, 0.1, 0.1, 0.1, 0.1, 0. (b) in slotted aloha, a station transmits in each time slot with a given probability. what probabilities would you assign to each of the four stations so as to: (i) maximize the efficiency of the protocol? (ii) maximize fairness among the four stations? (c) will the efficiency increase or decrease if we modify slotted aloha as follows: (i) get rid of slots and allow stations to transmit immediately? (ii) implement carrier sensing? (iii) implement collision detection? (iv) implement collision avoidance?