PARALLEL AND DISTRIBUTED COMPUTING

Transcription

1 PARALLEL AND DISTRIBUTED COMPUTING 2009/ st Semester Teste Jnury 9, 2010 Durtion: 2h00 - No extr mteril llowed. This includes notes, scrtch pper, clcultor, etc. - Give your nswers in the ville spce fter ech question. You cn use either Portuguese or English. - Be sure to write your nme nd numer on ll pges, non-identified pges will not e grded! - Justify ll your nswers. - Don t hurry, you should hve plenty of time to finish this test. Skip questions tht you find less comfortle with nd come ck to them lter on. I. (1,5 + 1,5 + 2 = 5 vl.) 1. Two of the dvntges hiled for Trnsctionl Memory over Exclusive Regions re tht it is optimistic nd composle. Explin wht is understood y these two terms y compring the workings of these two methods to solve rces in prllel progrms. Numer: Nme: 1/10

2 2. Argue out the est possile implementtion of the rodcst function in the following systems: ) uniform memory ccess (UMA) system. ) distriuted shred memory (DSM) system. c) distriuted memory system (multicomputer). Numer: Nme: 2/10

3 3. Consider tht the following progrm is running on 2 processors. int min() { #prgm omp prllel for schedule(dynmic, 4) for (i = 0; i < 10; i++){ printf ("i: %i\n", i); } #prgm omp prllel { printf("strting work\n"); // do some prllel work } } #prgm omp mster printf("proc: %i\n",omp_get_num_proc()); Is the following vlid output of this progrm? Justify your nswer, indicting ll the incoherences you my detect. i: 0 i: 1 i: 2 i: 5 i: 6 i: 8 i: 3 i: 4 i: 9 i: 7 strting work proc: 1 Numer: Nme: 3/10

4 II. (1, ,5 = 5 vl.) 1. Consider tht we hve the following MPI progrm running on 2 processors, N is equl to MPI_Comm_rnk (MPI_COMM_WORLD, &id); 2. if (id == 0) 3. for (i = 0; i < N; i++) 4. [i] = i; 5. MPI_Bcst(, N, MPI_INT, 0, MPI_COMM_WORLD); 6. for (i = 0; i < N; i++) 7. [i] = [i] + id; 8. MPI_Alltoll(, N, MPI_INT,, N, MPI_INT, MPI_COMM_WORLD); Indicte the vlues of the rrys nd on ech processor t the following execution points. (use? when not defined) PROCESS 0 PROCESS 1 Before executing line 5 Before executing line 6 Before executing line 8 Finl vlues: Numer: Nme: 4/10

5 2. Apply the Foster s methodology in the implementtion of shift y one it to the right of n imge in 2D itmp structure. Numer: Nme: 5/10

6 3. In some implementtions of the Work Pool model (lso known s Processor Frm model) for dynmic lod lncing there exist second-level mster nodes. Discuss the need for them nd how the role of the primry mster chnges. Numer: Nme: 6/10

7 III. (1,5 + 1,5 + 2 = 5 vl.) 1. Wht is the mening of otining 0 for the Experimentlly determined seril frction metric when evluting progrm on 2, 4, 8 nd 16 processors? 2. Discuss the following sttement: There re prolems for which it is possile to chieve prllel lgorithm with efficiency ove 100%. Numer: Nme: 7/10

8 3. Consider prolem with sequentil lgorithm tht runs in Θ(n log 2 n) nd with prllel implementtion whose overhed (communiction + redundnt computtion) per processor is given y Θ(n log n). If the required memory grows with n 2, compute the sclility function for this prllel lgorithm. Discuss the result otined. Numer: Nme: 8/10

9 IV. (1,5 + 1,5 + 2 = 5 vl.) 1. Consider tht we need to implement progrm to solve Bcktrck Serch prolem with rnching fctor = 3 nd tht we hve ville distriuted system with 32 processors. Argue out the est prllel implementtion for this prolem. 2. The sorting lgorithms Hyperquicksort nd Prllel Sorting y Regulr Smpling (PSRS) hve oth the sme complexity, O(n/p log n), nd the sme sclility function p c 1. Wht chrcteristic of PSRS mkes it preferle to Hyperquicksort? Numer: Nme: 9/10

10 3. Consider prllel lgorithm tht requires the exchnge of n cells etween ech pir of processors on every itertion. The following times re known: x: computtion time for single cell y: time required to crete one messge z: time to send one cell (hence, messge tht sends n cells tkes y + nz time) ) Otin n expression tht represents the overhed time (communiction + redundnt computtion) per itertion s function of the numer of ghostpoints. ) Descrie how you cn use this expression to determine the est numer of ghostpoints to use for this ppliction. Numer: Nme: 10/10