Added material for the Intro to OpenMP session

Author: raphaelmcobe

README.md

@@ -48,3 +48,7 @@ The programme specifically addresses the needs of scientists using, writing, or
 **Interfacing Multiple Programming Languages** [[Slides]](day2/multi-language.pdf) [[Code]](day2/multi-language) 
 
 **Floating Point Math and Errors** [[Slides]](day2/floating-point) [[Code]](day2/floating-point-code/)
+
+#### Day 3
+
+**Introduction to OpenMP** [[Slides]](day3/introduction-to-openmp.pdf) [[Code]](day3/introduction-to-openmp/)

day3/introduction-to-openmp.pdf

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <omp.h>
+int main() {
+
+    char hn[600];
+    int thi=10;
+    int thid=200;
+    int thid2=20;
+    int thid3=15;
+
+    printf("before Thread shared %d private %d firstprivate %d lastprivate %d \n", thi, thid, thid2, thid3);
+    #pragma omp parallel shared(thi) private(thid) firstprivate(thid2)
+    {
+        gethostname(hn,600);
+        printf("hello from hostname %s shared %d private %d firstprivate %d lastprivate %d \n",hn, thi, thid, thid2, thid3);
+	thi = omp_get_thread_num();
+	thid = omp_get_thread_num();
+	thid2 = omp_get_thread_num();
+    thid3 = omp_get_thread_num();
+        printf("hello from hostname %s shared %d private %d firstprivate %d lastprivate %d \n",hn, thi, thid, thid2, thid2);
+    }
+
+    printf("Outside Thread shared %d private %d firstprivate %d lastprivate %d \n", thi, thid, thid2, thid3);
+    return(0);
+}

day3/introduction-to-openmp/OMP-hello

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <omp.h>
+
+int main() {
+
+    printf(" omp_get_max_threads %d", omp_get_max_threads() );
+    printf(" omp_get_thread_limit %d", omp_get_thread_limit() );
+
+    char hn[600];
+    int ID = 0;		
+    #pragma omp parallel
+    {
+	ID = omp_get_thread_num();
+        gethostname(hn,600);
+
+        printf("hello from hostname %s Thread Number: %d\n",hn, ID);
+    }
+
+    printf("Executing with 4 threads");
+
+    #pragma omp parallel num_threads(4)
+    {
+	ID = omp_get_thread_num();
+        gethostname(hn,600);
+        printf("\nhello from hostname %s Thread Number: %d\n",hn, ID);
+    }
+
+    printf("Executing with 8 threads");
+    omp_set_num_threads(8);	
+    #pragma omp parallel 
+    {
+	ID = omp_get_thread_num();
+        gethostname(hn,600);
+        printf("\nhello from hostname %s Thread Number: %d\n",hn, ID);
+    }
+
+    return(0);
+}

day3/introduction-to-openmp/OMP-hello-PR-variable

@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main() {
+
+    char hn[600];
+
+    #pragma omp parallel
+    {
+        gethostname(hn,600);
+        printf("hello from hostname %s\n",hn);
+    }
+    return(0);
+}

day3/introduction-to-openmp/OMP-hello-PR-variable.c

@@ -0,0 +1,107 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <omp.h>
+#include <math.h>
+
+int main() {
+
+  double *a;
+  double *b;
+  double randV;
+  double lastx;
+  int i =0; 
+  int msize = 0;
+
+  //msize = 987456213; //16000;
+  msize = 1000; //16000;
+  randV = 0;
+
+  srand(time(NULL));
+  randV=rand();
+  randV=randV;
+
+  a = (double*) malloc(msize * sizeof(double));
+  for ( i = 0; i < msize; i++) {
+    a[i] = i/randV;
+  }
+
+  randV=rand();
+  randV=randV;
+  printf("randV %f\n", randV);
+
+  b = (double*) malloc(msize * sizeof(double));
+
+  int totthreads;
+  
+  totthreads=omp_get_num_threads();
+  totthreads=11;
+
+  int id=0;
+  int stepPThread;    
+  int stepLastThread;    
+  int begin;
+  int end;
+
+  #pragma omp parallel shared(totthreads) private(id, stepPThread, stepLastThread, begin, end)
+  {
+    id=omp_get_thread_num();
+    stepPThread=msize/totthreads;    
+    stepLastThread=msize % totthreads;    
+    begin = id*stepPThread;
+    end = (begin + stepPThread)-1;
+
+    int cmp = totthreads-1;
+
+    if (id == cmp) {
+      end = end + stepLastThread;
+      //printf("\n id %d cmp %d \n", id, cmp);       
+    }
+    //else
+      //printf("\n id %d cmp %d \n", id, cmp);
+
+    printf("totthreads %d id %d stepPThread %d stepLastThread %d begin %d end %d \n", totthreads, id, stepPThread, stepLastThread, begin, end);
+
+    for ( i = begin; i < end; i++) {
+      b[i] = i/randV;
+    }
+  }
+
+  #pragma omp parallel 
+  {
+    #pragma omp for
+    for ( i = 0; i < msize; i++) {
+      b[i] = i/randV;
+    }
+  }
+
+  #pragma omp parallel for
+  for ( i = 0; i < msize; i++) {
+    a[i] = a[i]+b[i];
+  }
+
+  lastx = 0;
+  for ( i = 0; i < msize; i++) {
+      lastx = a[i]+b[i] ;
+  }
+
+  printf("lastx SERIAL %f\n", lastx);
+
+  lastx = 0;
+  #pragma omp parallel for lastprivate(lastx)
+  for ( i = 0; i < msize; i++) {
+      lastx = a[i]+b[i] ;
+  }
+
+  printf("lastx lastprivate %f\n", lastx);
+
+  lastx = 0;
+  #pragma omp parallel for
+  for ( i = 0; i < msize; i++) {
+      lastx =  a[i]+b[i] ;
+  }
+
+  printf("lastx omp parallel for %f\n", lastx);
+ 
+  return(0);
+}

day3/introduction-to-openmp/OMP-hello-function

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(){
+
+  int nn, i;
+  nn = 2000000000;
+  double* a;
+  double* b;
+  double* c;
+
+  a = (double*) malloc(nn*sizeof(double));
+  b = (double*) malloc(nn*sizeof(double));
+  c = (double*) malloc(nn*sizeof(double));
+
+  #pragma omp parallel for
+  for( i=0; i<nn; i++) {
+    a[i] = i+i;
+    b[i] = i-i;
+    c[i] = i*i;
+  }
+
+  #pragma omp parallel for
+  for( i=0; i<nn; i++) {
+    a[i] = b[i] + c[i];
+  }
+
+  #pragma omp parallel for
+  for( i=0; i<nn; i++) {
+    b[i] = c[i] + a[i];
+  }
+
+  #pragma omp parallel for
+  for( i=0; i<nn; i++) {
+    c[i] = b[i] + a[i];
+  }
+
+}

day3/introduction-to-openmp/OMP-hello-function.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(){
+    int* input;    
+    int snum, i, sum;
+
+    sum = 0;
+    snum=40000000;
+    
+    input = (int*) malloc (sizeof(int)*snum);
+
+    for(i=0;i<snum;i++) {
+        input[i] = i+1;
+    }
+
+    #pragma omp parallel for
+    for(i=0;i<snum;i++)
+    {
+        int* tmpsum = input+i;
+                
+        //#pragma omp critical 
+        //{
+        //    sum += *tmpsum;
+        //}
+        #pragma omp atomic
+        sum += *tmpsum;
+
+    }
+    printf("sum %d", sum);
+}

day3/introduction-to-openmp/OMP-hello.c

@@ -0,0 +1,34 @@
+#include <omp.h>
+#include <stdio.h>
+
+int main () 
+{
+  int thid;
+
+  #pragma omp parallel private(thid)
+  {
+    #pragma omp master
+    {
+        thid=	omp_get_thread_num();
+        printf("master thread only: thread %d \n", thid);        
+    }
+
+    thid=	omp_get_thread_num();
+    printf("ALL threads: BE CAREFULL! thread  %d \n", thid);        
+        
+    #pragma omp barrier
+
+    #pragma omp single
+    {
+        thid=	omp_get_thread_num();
+        printf("some thread execute this part (only one): thread  %d \n", thid);        
+    }
+
+    #pragma omp barrier
+
+    thid=	omp_get_thread_num();
+    printf("after omp barrier! thread %d \n", thid);        
+  }
+
+  return 0;
+}

day3/introduction-to-openmp/OMP-helloOM

@@ -0,0 +1,15 @@
+#include <stdio.h>
+int main() {
+  #pragma omp parallel​
+  {
+    #pragma omp single​
+    {
+      #pragma omp task
+      printf("hello \n");
+
+      #pragma omp task
+      printf("again \n");
+    }
+  }
+  return(0);
+}

day3/introduction-to-openmp/OMP-loop-WorkSharing.c

@@ -0,0 +1,20 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+#define N 30
+
+int main ( ) {
+  unsigned long long fibs[N];
+
+  fibs[0] = fibs[1] = 1;
+
+  int i;
+  unsigned long long sum=2;
+  #pragma omp parallel for 
+  for (i = 2; i < N; i++) {
+    fibs[i] = fibs[i - 1] + fibs[i - 2];
+    printf("%llu \n", fibs[i]);
+  }
+
+  return 0;
+}

day3/introduction-to-openmp/OMP-matrix-sum

@@ -0,0 +1,31 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+unsigned long long fib(int n) {
+
+  unsigned long long i, j, res;
+
+  if (n < 2) return n;
+  
+  #pragma omp task shared(i)
+  i = fib(n-1);
+  #pragma omp task shared(j)
+  j = fib(n-2);
+
+  #pragma omp taskwait
+  return (i+j);
+}
+
+int main(){
+  int n = 80;
+  int c = 1;
+  #pragma omp parallel
+  {
+    #pragma omp single
+    {
+      for (c = 1; c <= n; c++) {
+        printf("%llu\n", fib(c));
+      }
+    }
+  }
+}