GCC with MASS;
Compilation command: gcc -o 2opt src/two_opt.c src/vnn.c src/util.c src/hill_climb.c -L/opt/ibm/xlmass/8.1.6/lib -I/opt/ibm/xlmass/8.1.6/include -lmassvp8 -lmass_simdp8 -lmass -lm -fopenmp -g -I./lib/ -Wall -O3 -mcpu=power8 -funroll-loops -ffast-math -mrecip=all -D __ibmxl__
---
Min distance found = 150331.471335

 Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

   51,93,16,13,967      cycles
 1,15,43,66,56,959      instructions              #    2.22  insn per cycle
   42,60,03,38,667      pm_flop

      14.841823305 seconds time elapsed

--- --- ---
With Flag added: mveclibabi=mass
---
Min distance = 150331.471335
Time taken = 14.680456

 Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

   51,38,64,48,591      cycles
 1,15,43,79,92,477      instructions              #    2.25  insn per cycle
   42,59,85,53,577      pm_flop

      14.704448017 seconds time elapsed
---------------------------------------------------------------------------------
xlC  with MASS:
Flags used: -O3 -lmassvp8 -lmass_simdp8 -qarch=pwr8
---
Min distance found = 150331.471335

Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

   41,78,74,85,042      cycles
   95,90,46,25,620      instructions              #    2.30  insn per cycle
   41,74,38,95,699      pm_flop

      11.944742810 seconds time elapsed
----------------------------------------------------------------------------------

GCC flags used: -lm -g -I./lib/ -Wall -O3
---
Execution: perf stat -e cycles,instructions,pm_flop -- ./2opt /root/Parth/tsplib/pcb3038.tsp
Min distance found = 150331.471335

 Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

 1,05,94,82,48,806      cycles
 1,10,06,42,09,701      instructions              #    1.04  insn per cycle
   30,84,23,39,755      pm_flop

      30.278379166 seconds time elapsed

----------------------------------------------------------------------
GCC flags used: -lm -g -I./lib/ -Wall -ffast-math
---
Min distance found = 150331.471335

 Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

 4,15,98,08,36,030      cycles
 4,39,97,72,28,466      instructions              #    1.06  insn per cycle
   36,26,21,59,981      pm_flop

     118.863982379 seconds time elapsed

-------------------------------------------------------------------------
GCC flags used: -lm -fopenmp -g -I./lib/ -Wall -ffast-math -O3
---
Min distance found = 150331.471335

 Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

   96,38,91,74,428      cycles
   83,00,93,99,457      instructions              #    0.86  insn per cycle
   25,39,55,14,615      pm_flop

      27.546819342 seconds time elapsed

---------------------------------------------------------------------------
GCC with MAAS;//incorrect compilation
flags used: -lm -O3 -ffast-math
---
Min distance found= 150331.471335

 Performance counter stats for './2opt /root/Parth/tsplib/pcb3038.tsp':

 1,24,32,41,09,471      cycles
 1,00,94,06,36,528      instructions              #    0.81  insn per cycle
   24,53,29,66,312      pm_flop

      35.528556756 seconds time elapsed

----------------------------------------------------------------------------

Conclusion: Accuracy is maintained in all the different compiler flags used. GCC with -O3 -ffast-math gives optimal time.
            But xlC performs better on POWER systems compared to gcc with time of around 12 sec with the same input.