The limitation of free float and safety float and the introduction of composite free float and composite safety float in CPM network

摘要

This paper analyzes the advantages and disadvantages of the two free float definitions and two safety float in CPM network. For free float, Definition 1 is put emphasis on without affecting the immediate succeeding activities;;no matter the immediate succeeding activities are dummy activities or real ones, therefore the responding calculation method is simple and regularity. However, the definition 1 may not meet the demand of optimization. While definition 2 can satisfy the demand of optimization, for it focus on without delaying the successor activities, except the successor dummy activities. But the calculate method of definition 2 is difficult. The situation is similar to safety float. This paper introduces the new concept of composite free float and composite safety float, absorbing the advantage of two definitions and conquering the disadvantages. So that the new concept not only easy to calculate but also convenient to apply in optimization.