Serial execution time

This simple modified Amdahl s law illustrates the incentives for optimal load balancing. The case(0,3000,0) corresponds to a hypothetical situation in which there is no serial execution time and no overhead for communication. The deviation from linear speed-up in this case (about 10%) is due only to load imbalance. 

An alternative to serial execution of operations is to split the total work into smaller groups, with each group carrying out its function simultaneously with the others (in a parallel fashion), viz., flows of instructions run in parallel (at the same time as each other). 

The speedup limit of 1// given by Amdahl s law is derived using the assumption that the fraction of serial code is independent of the problem size. It has been argued by Gustafson, however, that the serial fraction is likely to decrease when the problem size increases, and that the definition of the speedup should reflect this. Gustafson expressed the execution time on p processes and on a single process as follows... 

The efficiency of a parallel algorithm can be characterized by speed up S and total efficiency defined as [42] S = T jT, = Ts/ Tp, where n is the number of processors, while Ts and Tp are the execution times for serial and parallel algorithms, respectively. The total efficiency is less than 1 and can be written as a product of three factors [43] parallel efficiency, numerical efficiency and load-balancing efficiency. The parallel effidency is defined as = Tcomp/lTcomp + Tcornm), where Tcomp is the pure computation time and Tromm is the Communication time. 

The performance of a parallel algorithm is often assessed by comparing its execution time with that of a serial algorithm. Thus, one of the primary performance measures is the speedup S defined for a problem size n as the ratio of the execution time of a serial algorithm r(l,n) and that of a parallel algorithm r(np, n), running on p processors. The speedup is given by... 

Figure 7 Speed-up curves that are more representative of actual applications on the Intel Touchstone Delta Supercomputer. The ideal curve is also known as the linear speed-up curve. Each case is defined as casefT. , Tp raiiei overhead)- Except for the last case, each one grows as case(0(N), 0(N ), 0(N)) similar to a traditional Hartree— Fock application. The last case represents no serial time execution and no overhead for parallel computation. Therefore, the deviation from ideal performance is due only to the load imbalance in the application.

In contrast to a ID experiment, at the beginning of a 2D experiment a serial file containing a fixed number of blank FID data files is generated in persistent memory. The two dimensional matrix consists of tdl files, with a size of TD with each file corresponding to one time increment in the 2D matrix. A pointer is used to instruct the computer to transfer the accumulated data for each time increment from temporary memory to the correct persistent file. The pointer is then incremented for the next element. This whole procedure is executed by the pointer command if 0. The zd command occurs after the if 0 command and deletes the buffer contents. The 2D loop is closed by the command lo to label. In this instance label is a number or a string that is entered in the first position of the line where the next time increment in the 2D matrix will be started. 

Isolation means that operations of a transaction are not affected by other transactions that are executed concurrently, as if the separate transactions had been executed one at a time. The transaction must serialize all accesses to shared resources and guarantee that concurrent programs will not affect each other s operations. 

If a non-thread-safe function is called inside of a for loop, it is necessary to ensure that the function call is made by only one thread at a time. Such a critical section can be protected by a critical directive, which serializes the execution of the program block following it. In the following example, the progress of each thread is reported using printf... 

The calculation of the complete phonon spectrum of Germanium is in progress. The method described in the present paper was programmed for a vector computer (C.D.C. Cyber-205). Executing the same runs on a serial computer would take a prohibitively long computer time. Details of the vectorization of the phonon programs will be published elsewhere [l5l. 

Finally, there is the issue of vectorization, also referred to as scalar vs. parallel computing. Serial computers execute instructions sequentially, in specific order parallel machines execute multiple instructions simultaneously. Often, different flow domains are apportioned to different machines, and message passing interfaces must be designed so that these domains communicate with each other in an optimal way that minimizes computation time. Point relaxation gave way to line methods when serial computers were... 

A joint venture between Client and Contractor, which can be applicable to both traditional and integrated contracts, is the partnership or Alliance contract. In this type of contract the Client and the Contractor share one or more tasks in the process based on a best for project philosophy. This means that costs and risks are shared according to a predetermined division. The advantage is both parties share an interest to minimise risks and to find ways for cost savings. Another advantage is that, due to early Contractor involvement, the total project implementation time can be shortened since a number of activities can be executed in parallel instead of serially. Furthermore, the Client can draw upon Contractor s know-how and experience to get the necessary environmental licenses in place. 

Resource conflict resolution. A resource binding implies a cotain configuration of hardware sharing. In general, resource conflicts can arise when a resource is accessed simultaneously by multiple op tions. These conflicts can be resolved by serializing operations bound to the same resource that can otherwise execute in parallel. Timing constraints must still be satisfied after conflict resolution. 

Two operations opl and op2 are disjoint in time if one of the two following conditions holds (1) opl is serialized with respect to op2 in the graph, such that opl can execute only if opl has completed execution or vice versa, and (2) opl and opl each belong to different mutually exclusive branches of a conditional. The two cases are illustrated in Figure 7.1. Since the conditional branching structure cannot be arbitrarily altered without changing the external behavior of the model, we resolve resource conflicts by serializing operations. 

The following theorem provides an effective and exact pruning measure that is used in the exact conflict resolution algorithm, described in Section 7.3.2. The theorem states that the sum of the execution delays of the vertices to be serialized ( )) "0 exceed the allowed maximum timing constraint from... 

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