Create sum.c

sum.c

@@ -0,0 +1,111 @@
+// Maximum performance with optimal count of forks.
+// HOW TO BUILD
+// gcc summ.c -lpthread
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/sysinfo.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <semaphore.h>
+
+#define SEMAPHORES 1
+
+static long *main_result;
+static long *finished;
+
+long sumumatoru_kun (long start, long end)
+{
+  long num, digit, sum = 0;
+  while (end > start)
+  {
+    num = end;
+    while (num > 0)
+    {
+      digit = num % 10;
+      sum  = sum + digit;
+      num /= 10;
+    }
+    end--;
+  }
+  return sum;
+}
+
+int main(int argc, char *argv[])
+{
+  long end, start, first, last, shift, i, temp;
+  int p_pid = getpid();
+  long f_count = 2 * get_nprocs_conf();
+  pid_t pid;
+  main_result = mmap(NULL, sizeof *main_result,
+    PROT_READ | PROT_WRITE,
+    MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+  finished = mmap(NULL, sizeof *finished,
+    PROT_READ | PROT_WRITE,
+    MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+  sem_t *semaphore = mmap(NULL, sizeof(sem_t), PROT_READ | PROT_WRITE,
+             MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+  *main_result = 0;
+  *finished = 0;
+  start = 0;
+  sem_init (semaphore, 1, 1);
+  printf("This system has %d processors configured. Going to spawn %ld forks.\n",
+    get_nprocs_conf(), f_count);
+  if (argc < 2)
+  {
+    return 228;
+  }
+  end = strtoll(argv[1], NULL, 0);
+  if(f_count >= end)
+  {
+    f_count = 1;
+  }
+  shift = end / f_count;
+  i = 0;
+  while(i < f_count)
+  {
+    if(pid == 0){break;}
+    pid = fork();
+    if(i + 1 == f_count)
+    {
+      last = end;
+    }
+    else
+    {
+      last = (start + shift*i) + shift;
+    }
+    first = start + shift*i;
+    i++;
+  }
+    if(pid == 0)
+    {
+      printf("Child %d was started. My job is \t%ld \t%ld\n",
+        getpid(),
+        first,
+        last);
+      temp = sumumatoru_kun(first, last);
+      if (SEMAPHORES)
+        sem_wait(semaphore);
+      *main_result = *main_result + temp;
+      if (SEMAPHORES)
+        sem_post(semaphore);
+    }
+    else
+    {
+      i = f_count;
+    }
+  *finished = *finished + 1;
+  if(p_pid == getpid()){
+    while(*finished < f_count + 1)
+    {
+      usleep(10 * 1000);
+    }
+      if (SEMAPHORES)
+        sem_wait(semaphore);
+    printf("%d - Sumumatoru kun handled %ld forks and got result %ld\n",
+      getpid(), 
+      f_count,
+      *main_result);
+  }
+  return 0;
+}