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lets see highest response ratio next the name of name itself says that we are going to find something called a response ratio and now we show pulses having the highest of this we are going to take it so what is response ratio is waiting time plus service time by service time so W means waiting time for a process so for which means whenever you are standing at a point of time and till that point whatever is the waiting time that is called waiting time W here so W is not the final waiting time W is what is the waiting time at the point of your computation so whenever you are computing it at that point you find out the waiting time okay that is W and the Ness is service time or the birth time so s is nothing but the service time now for every process what we do is we find out this factor and now among all the process whichever is having this highest value we are going to pick it up right so here we are not purely depending on the first time we are depending on the birth time as well as waiting time so how are we depending is Ill see whenever this first time is less since whenever this birth time is less yes that will be having the higher value fine but along with that if a process has been waiting for a long time then that one will get the higher value isnt it so it is it is tricky but in understand this so if the job is having the ish hottest birth time that is going to get higher value along with that if the process is waiting for a long time that will also get the higher value so what is the main difference between shortage job position this one is in short a job we are all we were always taking the shortest possible job but here we are taking both the birth time as well as waiting that which means if a longer job if a job with our you know lot of burst time has been waiting for a long time then that could also get scheduled right like this and s is the service time which means series HR RS not only favors the shorter jobs why does it favor the shorter jobs because denominator it you know there is service time therefore less of these I am the factor beverage it favors the shorter jobs but also limits the waiting time of longer jobs which means it will not let it a job wait for a long time because they know because it is having a large burst time with the examples it will be clear mode is non pre-emptive non-preemptive means once we pick up a job we are going to run to completion so till a job completes you are not going to let it go right so that is what it is now take this example and we shall see how to you know how does this one works on this now at time zero I am going to start it at time zero I am going to start the process P naught and I will be running it till completion why it is non pre-emptive therefore at 3
and also act 3 is this process P naught gets completed now if we look at time 3 only one process has arrived by them which is P 1 therefore I do not have any other choice so I am just hitting P 1 and now what is it so P 1 is going to run for 6 units therefore no the time is 9 therefore by timeline all the remaining three are available 2 3 4 are available now which one should I pick among this that depends on the response ratio right now lets see the response ratio of each one response ratio of P 2 process 2 is what is the waiting time it came at 4 and now the time is 5 therefore what is the waiting for waiting time so far 9 minus 4 which is nothing but v right v plus then what is the disburse time Burstyn is 4 divided by 4 right which is nothing but 9 by 4 I think you will get 2.25 okay that is response ratio of p2 and now you can compute the response ratio for the process 3 so response ratio of process realz waiting time is nothing but it came at 6 and now the time is 9 therefore it waited for E+ birth time is 5 therefore divided with burst time right and what we get we get 8 by 5 right which is 1 point I think 6 1.6 yes okay and the next one is response ratio of 4 you have to find out all the response ratios of the process remaining right and now it came at 8 therefore it waited T for one because now the time is 9 and its a burst time is 2 therefore 3 by 2 is 1 point 5 so these are the response ratios of our second process thread process and forth process which one is having the highest response ratio this one right therefore I am going to pick up the second cross and schedule it so P 2 will be scheduled and how long does it run it will run for four units which means still 13 it is going to run and I should that okay now the time is 13 and quarter the process I have 3 & 4 so now I should compute again the response ratios of 3 & 4 response ratio of 3 is it arrived at 6 now the time is 13 therefore it waited for 7 units plus its burst time is 5 right by 2 so which is nothing but 12 by sorry 12 by 5 12 by 5 so this is to 0.5 hmm 12 I for 12 by 5 I think it is 2.5 of 2.4 yeah and now response ratio of 4:1 is 4th processes here it came at 8 and all the time is 13 therefore it is 5 plus what is the first time first time is 2 divided by 2 which is 7 by 7 by 23.5 so 3.5 is very much higher right so three-pointer is very much higher than this value therefore you are going to schedule p 4 first p 4 and it is going to run till time five minutes therefore till 18 and then I am going to next should you pp3 that is the only job
remaining now p3 needs how much time p3 needs if you observe it 5 times 5 right Oh p4 needs only 2 units therefore deserve some 13 it is going to run till only 15 let me just check it P not requires three units p1 require 6 units p2 requires 4 units p4 requires 2 units only 2 units and then p3 requires 5 units which means still 20 right so this is how HR RN is going to shed you the process now if you want to see what is the difference between hrrm and shortage of first let us see the Gantt chart for shortest job as well this is this is the Gantt chart for HR RN highest response ratio next let us see it for the other one has the shortage of first that we use some insight about it now coming to this shortest job first so initially nothing will change because only one cross is available so I am going to take it and shred unit nothing is going to change and at time 3 only one more cross is available therefore I am going to shade you it nothing is going to change and p1 is how much 9 right at this point all the process are available then if we use shortage of first which one will be shochet Joule first P 4 will be scheduled isnt it because among the remaining process P 4 is having the shortest one right and then now and then what will be scheduled after P for the next one that will get scheduled is the p2 and then after p2 is next one that will be scheduled is p3 therefore if you watch it the order in which they get should they got schedule has changed right especially this P 2 P 4 and P 4 P 2 right so even though even though P 4 is having a higher you know see this lower lower bus time P 2 is favored the reason is P 2 has been a long time PETA has arrived at four and it is waiting till you know 13 then you know it is better that you give it the chance the reason is this if a longer process has come earlier and it has been waiting for a long time it is really unfair to we dont give the chance to a shorter process which has which came very late right so therefore HR aren is going to have some benefits over sjf anyway again here also the same same disadvantage persist what is the disadvantage you cannot implement this because you want these births tends to be given well ahead but then the problem is we cannot get the birth times therefore it is also it cannot be implemented practically but theoretical yes and maybe if you would guess the burst times by using some methods like process size process type or static dynamic it is okay you can implement it but anyway most of their no operating system most of the opera systems do not use this I want you see most favorable one so however these algorithms which are based on burst times will give you the best performance possible and they can be used to measure the performance against the others which means they are there nothing
but D you can think of them as we you know measuring scale so you know this they are going to be the you know some kind of scale and everything else is measured against rate if the performance of shortage job first is so and so your algorithm is going to be this so it is close to this it might be best like that right fine let us compute the completion time under all time and waiting time and finish it out so completion time is this so I am talking about HRM so if you watch it completion time is C since this is non pre empty we can go either from the right side or left side not an issue so completion time of P naught is 3 and completion time of P 1 is 9 and completion time of P 2 is 13 completion time of P 4 is 15 completion time of pop3 is 20 height P 3 is 20 and the completion time of P 4 is 15 lets check this P naught is 3 P 1 is 9 P 2 is 13 P 3 is 20 P 4 is 15 right and also finding out the completion time we are supposed to find out the turnaround time rather all time is completion time – arrival time so how much is this here it is 3 and here it is 7 here it is 9 here it is 14 and here it is how much is it 7 read it okay and then you can find out the waiting time so what is waiting down here the waiting time is turnaround time – arrival time which is three turn around Emmas birth time which is zero here right and then tother on time is 7 and the bust and so it is 1 and then it is 5 it is 9 it is 5 right so this is a waiting time and you can find out what is the average turnaround time and what is the average waiting time and if you want to find out the response time also you could find it out see this what is the response ratio of P not it arrived at 0 and it what should you remediated it for response time is 0 what is the response time of P 1 it arrived at 2 and it got scheduled at 3 therefore response time is 1 what about P 2 it arrived at P 2 arrived at 4 and it caught scheduled at 9 therefore response time is 5 and then P 3 P 3 arrived at tub 8 and it got scheduled at 15 therefore its response time is 7 and P 4 arrived at 8 o p3 error at 6 I am wearing a suit only between P 3 and before okay P 3 error at 6 and then it got scheduled at the 15 therefore o 6 and how much nine I think response time is 9 and what about this one p4 arrived at eight and it was should you like 13 therefore its response time is 5 right so this is also response time you can find out the average response time as well what if so that is what I was saying response ratio is HR and is better compared to SJ ok
Operating System (Software Genre), Process times
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