subject
Physics, 27.07.2019 00:20 notgoodatmath5379

Amultiprocessor machine has 1024 processors. on this machine we map a computation in which n iterate values must be computed and then exchanged between the processors. values are broadcast on a bus after each iteration. each iteration proceeds in two phases. in the first phase each processor computes a subset of the n iterates. each processor is assigned the computation of k = n/p iterates, where p is the number of processors involved. in the second, communication phase each processor broadcasts its results to all other processors, one by one. every processor waits for the end of the communication phase before starting a new computation phase. let t c be the time to compute one iterate and let t b be the time to broadcast one value on the bus. we define the computation-to-communication ratio r as t c /t b . note that, when p = 1, no communication is required. at first, we use the premise of amdahl’s speedup (i. e., the same workload spread across an increasing number of processors). under these conditions: (a) compute the speedup as a function of p and r, for k = 1, 2, . . , 1024. (b) compute the maximum possible speedup as a function of p and r. (c) compute the minimum number of processors needed to reach a speedup greater than 1 as a function of p and r. second, we use the premise of gustafson’s law, namely that the uniprocessor workload grows with the number of processors so that the execution time on the multiprocessor is the same as that on the uniprocessor. assume that the uniprocessor workload computes 1024 iterates. (d) what should the size of the workload be (as a number of iterates) when p processors are used, as a function of p and r? pick the closest integer value for the number of iterates. (e) reconsider (a)–(c) above in the context of growing workload sizes, according to gustafson’s law. third, we now consider the overhead needed to broadcast values over the bus. because of software and bus protocol overheads, each bus transfer requires a fixed amount of time, independent of the size of the transfer. thus the time needed to broadcast k iterate values on the bus by each processor at the end of each iteration is now t 0 + k × t b . (f) using the constant workload size assumption (as in amdahl’s law), what is the maximum possible speedup? (g) using growing workload size assumption (as in gustafson’s law), what is the maximum possible speedup?

ansver
Answers: 1

Other questions on the subject: Physics

image
Physics, 22.06.2019 15:30, Mhayslett12
To understand the electric potential and electric field of a point charge in three dimensions consider a positive point charge q, located at the origin of three-dimensional space. throughout this problem, use k in place of 14? ? 0. part adue to symmetry, the electric field of a point charge at the origin must point from the origin. answer in one word. part bfind e(r), the magnitude of the electric field at distance r from the point charge q. express your answer in terms of r, k, and q. part cfind v(r), the electric potential at distance rfrom the point charge q. express your answer in terms of r, k, and q part dwhich of the following is the correct relationship between the magnitude of a radial electric field and its associated electric potential ? more than one answer may be correct for the particular case of a point charge at the origin, but you should choose the correct general relationship. a)e(r)=dv(r)drb)e(r)=v(r)rc)e(r)=? dv(r)drd)e(r)=? v(r)r
Answers: 2
image
Physics, 22.06.2019 17:30, masonorourke
Describe cytokinesis in plants and animals. in animals: in plants.
Answers: 2
image
Physics, 22.06.2019 22:50, cbogrett
Cyclotrons are widely used in nuclear medicine for producing short-lived radioactive isotopes. these cyclotrons typically accelerate h- (the hydride ion, which has one proton and two electrons) to an energy of 5 mev to 20 mev. this ion has a mass very close to that of a proton because the electron mass is negligible—about 1 2000 of the proton’s mass. a typical magnetic field in such cyclotrons is 1.9 t. (a) what is the speed of a 5.0-mev h-? (b) if the h- has energy 5.0 mev and b = 1.9 t, what is the radius of this ion’s circular orbit?
Answers: 1
image
Physics, 23.06.2019 00:30, ldelgado97
Due in 40 explain in terms of frame of reference if you’re inside a moving train everything on the outside can seem to be moving
Answers: 1
You know the right answer?
Amultiprocessor machine has 1024 processors. on this machine we map a computation in which n iterate...

Questions in other subjects:

Konu
Mathematics, 20.10.2019 19:20