lecture 9.pptx - Lecture 9 Parallel Computation Computation...

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Lecture 9
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Parallel Computation Computation Structure for Parallel Computation op Start End 0 time 0 time Absorbing control node t time test Start control node Stop control node Operation node Test node Or node, also called Junction node Many in, One out For parallel computation, need to generate threads, one where a parent produces children: a fork node to create threads. The corresponding join node, also called “and” node or synchronization node , equivalently, is the node where parallel threads come together into one. It is called an and node because need all control signals to arrive at join before outgoing control signal generated.
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These two nodes are designed to be put together with operations t n time Fork Join op1 opn . . . t 1 time In this parallel structure, each thread has its own time.
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Performance Analysis of Parallel Structures Fork C1 Cn Join e 1 e 1 = e 1 e 1 PS C=C FORK + C JOIN + max(C 1 , C 2 , …C n )
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1 Fork Join 2 3 e 3 4 5 e 2 V Need to find the execution time of every branch (thread) Each branch is treated as a separate computation e 1
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Given the value of the flows e1, e2 What is the execution time of this branch? Total number of iterations is e2 The number of traversal of the branch is e1 The average number of iterations per traversal is e2/e1 The execution time of the branch = e2/e1 * C 5 + (1+e2/e1) * C 4 4 5 e 2 V e1
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e1 Probability of the right branch = e3 /e1 Probability of the left branch = (e1-e3) / e1 The execution time of the IF statement = e3/e1 * C3 + (e1-e3)/e1 C2
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