G carlsson u of mn isye lsb 1 lfa 3 lsa 0 lecture

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Unformatted text preview: = 1 LF(A) = 3; LS(A) = 0 Lecture 7: PERT & CPM October 3/17, 2013 21 / 38 Complete network layout D S=[0,7] F=[3,10] H S=[3,10] F=[4,11] A S=[0,0] F=[3,3] START B S=[0,1] F=[2,3] E S=[3,3] F=[5,5] F S=[5,5] F=[9,9] G S=[9,9] F=[11,11] I S=[11,11] F=[13,13] J S=[13,13] F=[17,17] END C S=[0,9] F=[4,13] J. G. Carlsson, U of MN ISyE Lecture 7: PERT & CPM October 3/17, 2013 22 / 38 Assembling a schedule Given a project network, a sensible practice for scheduling is as follows: . Write the critical activities first, staggered sequentially to ensure that the 1 project is completed within its specified duration . The non-critical activities have time spans greater than their respective 2 durations; schedule them as early as possible, leaving as much time as possible: Scheduled time = [ES, LF] D S=[0,7] F=[3,10] H S=[3,10] F=[4,11] A S=[0,0] F=[3,3] START B S=[0,1] F=[2,3] E S=[3,3] F=[5,5] F S=[5,5] F=[9,9] G S=[9,9] F=[11,11] I S=[11,11] F=[13,13] J S=[13,13] F=[17,17] END C S=[0,9] F=[4,13] J. G. Carlsson, U of MN ISyE Lecture 7: PERT & CPM October 3/17, 2013 23 / 38 Assembling a schedule D S=[0,7] F=[3,10] H S=[3,10] F=[4,11] A S=[0,0] F=[3,3] START B S=[0,1] F=[2,3] E S=[3,3] F=[5,5] F S=[5,5] F=[9,9] G S=[9,9] F=[11,11] I S=[11,11] F=[13,13] J S=[13,13] F=[17,17] END C S=[0,9] F=[4,13] Remark In the preliminary schedule, precedence constraints are not necessariliy satisfied (e.g. D→H) J. G. Carlsson, U of MN ISyE Lecture 7: PERT & CPM October 3/17, 2013 24 / 38 Floats Floats are the slack times available within the allotted span of a non-critical activity The two most common types are the total float and the free float: Total float is the amount of slack that an activity can afford without affecting the total project completion time: TF = LF − EF = LS − ES Free float is the amount of slack that an activity can afford without affecting the earliest start time of its subsequent tasks: FF = ES(successor) − EF J. G. Carlsson, U of MN ISyE Lecture 7: PERT & CPM October 3/17, 2013 25 / 38 Floats The total float of activity C is (14 − 8) = (11 − 5) = 6 The free float of activity C is 13 − 8 = 5 J. G. Carlsson, U of MN ISyE Lecture 7: PERT & CPM October 3/17, 2013 26 / 38 Quiz Which of the following are true? . All tasks with zero free float are critical. 1 . All tasks with zero total float are critical. 2 . All critical tasks have zero free float. 3 . All critical tasks have zero total float. 4 J. G. Carlsson, U of MN ISyE Lecture 7: PERT & CPM October 3/17, 2013 27 / 38 Quiz Which of the following are true? . All tasks with zero free float are critical. 1...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.

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