Fix off by one error

mpi_pi_cpu/mpi_pi_cpu.c

@@ -31,8 +31,8 @@ void main(int argc, char** argv) {
         gettimeofday(&start, NULL);
     }
 
-    istart = NPTS * rank;
-    iend = NPTS * (rank + 1);
+    istart = NPTS * rank + 1;
+    iend = NPTS * (rank + 1) + 1;
     sum = 0.0;
     for (i = istart; i <= iend; ++i) {
         sum += 0.5 / ((i - 0.75) * (i - 0.25));