Parallel development II 11/5/18

Transcription

1 Parallel development II 11/5/18

2 Administrivia HW 6 due tonight (heat diffusion in MPI) Final project Worth ~2 homeworks (35 points) and should have this scope Work individually or in teams of two (team = larger scope) Friday 11/9: Idea and resources you expect to use Wednesday 11/14: Presentation in class Tuesday 11/20 10pm: Final submission Ideas: CUDA w/ blocking, MPI+X, Parallel programming languages (e.g. Chapel), full implementation of one of the example projects, any bigger project in one of the paradigms we discussed, cross paradigm comparison

3 Administrivia HW 6 due tonight (heat diffusion in MPI) Final project Worth ~2 homeworks (35 points) and should have this scope Work individually or in teams of two (team = larger scope) Friday 11/9: Idea and resources you expect to use Wednesday 11/14: Presentation in class Tuesday 11/20 10pm: Final submission Ideas: CUDA w/ blocking, MPI+X, Parallel programming languages (e.g. Chapel), full implementation of one of the example projects, any bigger project in one of the paradigms we discussed, cross paradigm comparison

4 Recall: N-body problem

5 Recall: The book presents the forces as a matrix where f ij is the force of particle j on particle i. What is true about this matrix? A. It is symmetric, i.e. f ij = f ji (actually skew-symmetric, with f ij = -f ji ) B. The diagonal entries f ii are constant (actually 0) C. The row values are non-decreasing, i.e. f ij >= f i,j+1 D. The row values are non-increasing, i.e. f ij <= f i,j+1 E. Not exactly one of the above

6 When computing the upper half of the force matrix (shown below), if we only parallelize the outer loop, how should it be scheduled? for each particle q for each particle k > q A. Static, without a chunk size specified B. Static, with a large chunk size C. Static, with a small chunk size D. None of these is good E. More than one of A,B,C are good

7 When computing the upper half of the force matrix (shown below), if we only parallelize the outer loop, how should it be scheduled? for each particle q for each particle k > q A. Static, without a chunk size specified B. Static, with a large chunk size C. Static, with a small chunk size D. None of these is good E. More than one of A,B,C are good

8 In the MPI version of the program, what is a ring pass? A. A new collective operation B. A way that particles move around a logical ring C. A way for particles to take turns by passing a virtual token around a logical ring D. An approach in which each particle only does detailed calculations with nearby particles E. Not exactly one of the above

9 In the MPI version of the program, what is a ring pass? A. A new collective operation B. A way that particles move around a logical ring C. A way for particles to take turns by passing a virtual token around a logical ring D. An approach in which each particle only does detailed calculations with nearby particles E. Not exactly one of the above

10 Tree search (for TSP) A B C D

11 Tree search (for TSP) A B A C D A,B A,C A,D A,B,C A,B,D

12 What is included in the parallel overhead for this program? A. Trying each possible next city B. Assigning different subtrees to each thread C. Copying the tour so far to store it in the stack D. Comparing the cost of a partial tour to the cost of the best-known tour E. Not exactly one of the above

13 What is included in the parallel overhead for this program? A. Trying each possible next city B. Assigning different subtrees to each thread C. Copying the tour so far to store it in the stack D. Comparing the cost of a partial tour to the cost of the best-known tour E. Not exactly one of the above (B&C)

14 Macros Programming shorthand implemented using text substitution int Tour_city(tour_t tour, int i) { } return tour -> cities[i]; #define Tour_city(tour, i) (tour->cities[i])