Merge branch 'master' of gitlab.rc.uab.edu:ravi89/Tutorial_parallelism

README.md

+This repository contains a variety of examples of parallelism.
+
+MATLAB
+in the example script provided, "parforExample.m", the "for" command can be switched between "for" and "parfor". Changing to "parfor" will ask MATLAB to parallelize the loop if possible. In MATLAB r2018a, parpool is called by MATLAB with 12 threads as default if parfor is used without first calling parpool.
+
+R
+The text in Rparallel.txt is a set of R commands to be used to test out one version of parallelism in R. 

Rparallel.txt

+install.packages("plyr")
+install.packages("doMC")
+
+
+library(plyr)
+library(doMC)
+doMC::registerDoMC(cores=24) # or however many cores you have access to
+
+system.time(ddply(iris, .(Species), function(x) {
+ Sys.sleep(2)
+ nrow(x)
+}))
+# user system elapsed
+# 0.005 0.001 6.016
+
+system.time(ddply(iris, .(Species), function(x) {
+ Sys.sleep(2)
+ nrow(x)
+}, .parallel = TRUE))
+# user system elapsed
+# 0.018 0.015 2.031

parforExample.m

+% Testing number of prime numbers in a given range
+
+final=10^7;        %upper limit
+close all
+%clear all
+tic
+count=[];
+ratios=[];
+l=[];
+out=[];
+
+disp('Please wait.. Finding number of primes.... ')
+a=0;
+parfor i=1:final
+ 
+  c=isprime(i);
+   if c==1
+       i;
+       a=a+c;
+   end
+end
+a;
+ratio=a/final;
+l=[l,final];
+count=[count,a];
+ratios=[ratios,ratio];
+
+
+out=[l',count',ratios'];
+toc
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