Scheduling collective communications (CC) in networks based on optimal graphs and digraphs has been done with the use of the evolutionary techniques. Inter-node communication patterns scheduled in the minimum number of time slots have been obtained. Numerical values of communication times derived for illustration can be used to estimate speedup of typical applications that use CC frequently. The results show that evolutionary techniques often lead to ultimate scheduling of CC that reaches theoretical bounds on the number of steps. Analysis of fault tolerance by the same techniques revealed graceful CC performance degradation for a single link fault. Once the faulty link is located, CC can be re-scheduled during a recovery period. Categories and Subject Descriptors I.2.8 [Artificial intelligence]: Problem Solving, Control Methods and Search – heuristic methods, scheduling. General Terms Algorithms, Performance, Design. Keywords Collective communications, communication scheduling, evo...