What is crew variant pram?
Concurrent Read Exclusive Write (CREW): This PRAM variant allows concurrent reads but not concurrent writes to shared memory locations. All processors concurrently reading a common memory location obtain the same value.
What is work in parallel algorithm?
On a parallel machine, the work is simply the processor-time product. Hence, an algorithm that takes time t on a P-processor machine performs work W = Pt.
What is work optimal?
A parallel algorithm for a problem is said to be optimal if its total number of operations is asymptotically the same as that required by the fastest sequential algorithm for the problem. An optimal algorithm is said to be work-time optimal if its time is the best possible (i.e., matches a lower bound).
What is pram and stroller?
The terms “pram” and “stroller” tend to be used fairly loosely and can be used for the same product. “Stroller” often refers to a model with an upright seat while “pram” refers to one with a bassinet or flat sleeping surface, but these days most models allow both positions.
What is parallel algorithm example?
Examples include many algorithms to solve Rubik’s Cubes and find values which result in a given hash. Some problems cannot be split up into parallel portions, as they require the results from a preceding step to effectively carry on with the next step – these are called inherently serial problems.
What is all to one reduction?
The dual of one-to-all broadcast is all-to-one reduction. In all-to-one reduction, each processor has m units of data. These data items must be combined piece-wise (using some associative operator, such as addition or min), and the result made available at a target processor.
How do you calculate parallel time?
The speedup gained from applying n CPUs, Speedup(n), is the ratio of the one-CPU execution time to the n-CPU parallel execution time: Speedup(n) = T(1)/T(n). If you measure the one-CPU execution time of a program at 100 seconds, and the program runs in 60 seconds with 2 CPUs, Speedup(2) = 100/60 = 1.67.