speed comparison of Fortran internal read with Fortran calling C atoi() function
Sources are compiled with the -O3 option for gfortran and Intel Fortran on Windows. Here are the run times in seconds
gfortran ifort source
12.770 3.549 xread_int.f90
14.456 2.949 xread_int_fmt.f90
0.416 0.362 xatoi_loop.f90