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d1 bubble sort, please help! watch

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    (Original post by Clarity Incognito)
    Activity 6?

    If you're asking whether I agree with the yellow boxes, I do but the one talking about activity F is hidden from view so I can't confirm that one.

    *No worries *

    EDIT: Answers for question 1 should be:

    a) C and E
    b) I and J
    c) F, H and I

    i'm sorry I meant:
    why doesn't activity E have to be happening on day 8?
    here's the link: http://tinypic.com/view.php?pic=15ochw2&s=6

    and for the second one:
    http://tinypic.com/view.php?pic=m9x6hz&s=6
    mid day on day 10, is the line supposed to be drawn that way iteself?

    and why does activity E have to be happening on day 10? is there any hard and fast rule? the duration of activity E is 11 days and it has to finish at the end of day 18..so is it because the float of E isn't big enough? (the dotted lines)
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    (Original post by Clarity Incognito)
    Activity 6?

    If you're asking whether I agree with the yellow boxes, I do but the one talking about activity F is hidden from view so I can't confirm that one.

    *No worries *

    EDIT: Answers for question 1 should be:

    a) C and E
    b) I and J
    c) F, H and I

    and the answers for 1 as per the book are:
    a- C D E F
    b- J I
    c- J F H I
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    (Original post by zomgleh)
    i'm sorry I meant:
    why doesn't activity E have to be happening on day 8?
    here's the link: http://tinypic.com/view.php?pic=15ochw2&s=6

    and for the second one:
    http://tinypic.com/view.php?pic=m9x6hz&s=6
    mid day on day 10, is the line supposed to be drawn that way iteself?

    and why does activity E have to be happening on day 10? is there any hard and fast rule? the duration of activity E is 11 days and it has to finish at the end of day 18..so is it because the float of E isn't big enough? (the dotted lines)
    Activity E MUST be happening on day 8. It MUST be happening day 8 because no matter what day activity E starts, its duration covers day 8. EDIT: Yeah, you're right, the answer is wrong.

    The line should really be drawn one unit to the right.

    The part I've bolded above is the reason.
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    (Original post by zomgleh)
    and the answers for 1 as per the book are:
    a- C D E F
    b- J I
    c- J F H I
    I disagree with the book. My thinking?

    D can start on day 9.

    F can start on day 15. The don't HAVE to be happening on day 8.

    Concerning part c) J MUST be happening on day 22, whether this is included under the term 'may' I'm not sure. It shouldn't be.
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    (Original post by zomgleh)
    here: http://www.srepapmaxeeeerf.org/A%20L...nuary_2010.pdf


    do you know if this is correct?
    http://tinypic.com/view.php?pic=15ochw2&s=6
    thanks
    and no, i don't understand those questions.
    i actually suck at D1.
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    (Original post by Clarity Incognito)
    I disagree with the book. My thinking?

    D can start on day 9.

    F can start on day 15. The don't HAVE to be happening on day 8.

    Concerning part c) J MUST be happening on day 22, whether this is included under the term 'may' I'm not sure. It shouldn't be.
    i agree with you.
    here's a simliar past paper question:
    http://tinypic.com/view.php?pic=11823ae&s=6
    and the answer to that:
    http://tinypic.com/view.php?pic=nx3mgk&s=6

    i don't quiet get part (e) List the activities that must be happening on day 20.
    also, for drawing a scheduling diagram (part g), what are the rules to follow? the text book hardly gives any explanation
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    (Original post by zomgleh)
    i agree with you.
    here's a simliar past paper question:
    http://tinypic.com/view.php?pic=11823ae&s=6
    and the answer to that:
    http://tinypic.com/view.php?pic=nx3mgk&s=6

    i don't quiet get part (e) List the activities that must be happening on day 20.
    also, for drawing a scheduling diagram (part g), what are the rules to follow? the text book hardly gives any explanation
    For part e) we have earliest and latest start times right? We want to know all the activities, which are happening on day 20, i.e. those activities whose duration is definitely happening on day 20.

    Activity D starts on day 10 (earliest and latest) and finishes day 20 so it has to be happening on day 20. If you look at the scheduling diagram (I know that the question is after this one but just look at it so you're clear when things are, it will make it clear that activity D finishes on day 20).

    For a scheduling diagram. You have worker A complete all the critical activites, you wrote down a critical path earlier, it has to be continuous and there shouldn't be any gaps because all the activities are critical. The rest of the workers are now put to work when there is an available activity, the criteria for choosing which activity comes first when you have a choice is that you choose the activity, which has the earliest latest start time, if that makes sense. Say we have activity G with start time (5,8) and activity H with start time (5,10) we choose G because it has the earliest latest start time out of the two.
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    (Original post by Clarity Incognito)
    For part e) we have earliest and latest start times right? We want to know all the activities, which are happening on day 20, i.e. those activities whose duration is definitely happening on day 20.

    Activity D starts on day 10 (earliest and latest) and finishes day 20 so it has to be happening on day 20. If you look at the scheduling diagram (I know that the question is after this one but just look at it so you're clear when things are, it will make it clear that activity D finishes on day 20).

    For a scheduling diagram. You have worker A complete all the critical activites, you wrote down a critical path earlier, it has to be continuous and there shouldn't be any gaps because all the activities are critical. The rest of the workers are now put to work when there is an available activity, the criteria for choosing which activity comes first when you have a choice is that you choose the activity, which has the earliest latest start time, if that makes sense. Say we have activity G with start time (5,8) and activity H with start time (5,10) we choose G because it has the earliest latest start time out of the two.
    but if you take a look at the example they've done, that doesnt seem to follow the same criteria (for a schedule), here:
    http://tinypic.com/view.php?pic=2poqgpx&s=6

    i calculated the "latest time" for each-
    B= 7
    D=16
    E=18
    F=23
    H=23
    I=25

    so after listing all the critical activities, the worker must start B and then D and then E right?
    so why can't the 2nd worker do B D AND E? why instead does he do B,D,F?
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    (Original post by zomgleh)
    so after listing all the critical activities, the worker must start B and then D and then E right?
    so why can't the 2nd worker do B D AND E? why instead does he do B,D,F?
    Worker 2 would do B, D and E in that order if there were only 2 workers.

    BUT there are three workers, they are all working together, you complete the scheduling diagram moving from left to right with the available workers. You do not schedule activities for one worker, you are scheduling for all of them at the same time so they can complete the job in the shortest time possible. As soon as an activity becomes avaialble, any available worker can commence it, if there is a choice of two activities but only one worker, you choose the activity with the earliest latest start time.
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    (Original post by Clarity Incognito)
    Worker 2 would do B, D and E in that order if there were only 2 workers.

    BUT there are three workers, they are all working together, you complete the scheduling diagram moving from left to right with the available workers. You do not schedule activities for one worker, you are scheduling for all of them at the same time so they can complete the job in the shortest time possible. As soon as an activity becomes avaialble, any available worker can commence it, if there is a choice of two activities but only one worker, you choose the activity with the earliest latest start time.
    so then why can't the 2nd worker just do- b d e
    and the third- F H I?
    i dont understand how they've chosen the combination of the second worker to be B D F instead of B D E? does it have anything to do with their duration?
    Also, what would be wrong if worker 2 would do, say, B H I?


    and even if the 3rd worker does E,why can't the 3rd worker start activity E before the 6th day?

    i'm sorry i'm just really confused
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    (Original post by zomgleh)
    so then why can't the 2nd worker just do- b d e
    and the third- F H I?
    i dont understand how they've chosen the combination of the second worker to be B D F instead of B D E? does it have anything to do with their duration?
    Also, what would be wrong if worker 2 would do, say, B H I?


    and even if the 3rd worker does E,why can't the 3rd worker start activity E before the 6th day?

    i'm sorry i'm just really confused
    The latest start time of E is day 7. When worker 2 has finished activity D on day 13, it's too late for him to start activity E because the latest start time of E was day 7.
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    (Original post by Clarity Incognito)
    The latest start time of E is day 7. When worker 2 has finished activity D on day 13, it's too late for him to start activity E because the latest start time of E was day 7.

    how do you get the latest start time for E?
    isn't it 6 and not 7?
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    (Original post by zomgleh)
    how do you get the latest start time for E?
    isn't it 6 and not 7?
    Earliest start time for E is 6. Latest start time for E is 7. There a total float of 1 day for activity E.
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    (Original post by Clarity Incognito)
    Earliest start time for E is 6. Latest start time for E is 7. There a total float of 1 day for activity E.
    so for any activity, the diff between earliest start and latest start time = float of activity?
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    (Original post by zomgleh)
    so for any activity, the diff between earliest start and latest start time = float of activity?
    :yep:

    I would advise you to read through your textbook thoroughly (I assume you have one) and then start doing past paper questions etc. and then you know where to refer to in the book in refresh your memory. Feel free to continue to use this thread though but I feel that it would benefit you more to just read through your textbook.
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    (Original post by Clarity Incognito)
    :yep:

    I would advise you to read through your textbook thoroughly (I assume you have one) and then start doing past paper questions etc. and then you know where to refer to in the book in refresh your memory. Feel free to continue to use this thread though but I feel that it would benefit you more to just read through your textbook.
    i did, but it says-
    latest finish time-duration-earliest start time=float.
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    (Original post by zomgleh)
    i did, but it says-
    latest finish time-duration-earliest start time=float.
    :facepalm: yeah you're right.

    I was talking about the slack.

    Float(i,j) = [ l_j - e_i - duration of (i,j)]

    Slack -  s_i = l_i - e_i
 
 
 
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