.. title: PAR Homework 3, Thu 2022-01-27
.. slug: homework03
.. tags: homework
.. date: 2022-01-27
.. category: 
.. link: 
.. description: 
.. type: text
.. has_math: true

Rules
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#. Due next Thu 2022-02-03

#. Submit the answers to Gradescope.

#. You may do homeworks in teams of 2 students.   Create a gradescope team and make one submission with both names.

Questions
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#. (10 pts) Investigate the effects of varying numbers of threads on elapsed time and errors.   Test sum, sum_atomic, sum_crit, sum_reduc with 1, 2, 8, 16, 32, 64 threads.  Make appropriate mods so that the programs run slowly enough for you to measure the elapsed times.

#. (10 pts) Look at https://docs.nvidia.com/hpc-sdk/compilers/hpc-compilers-user-guide/index.html#openmp-use

   Try to modify sum_atomic and sum_crit to run on the GPU (using OpenMP).  Full points for a good try, whether or not you succeed.

#. (5 pts) Why is matmul4 segfaulting on n=1000?  Try to fix it.

Total: 25