add 2nd zfft benchmark

Author: cval26

example/bench1.f90 renamed to example/bench01_zfft.f90

@@ -13,6 +13,7 @@ program bench1
 call random_number(x)
 z = x
 
+print *, "01: Benchmarking zfft"
 print *, "Initializing"
 call cpu_time(t1)
 call zffti(N, w)
@@ -38,4 +39,5 @@ program bench1
 print *, "Init time: ", time_init
 print *, "Forward time: ", time_forward
 print *, "Backward time: ", time_backward
+print *, ""
 end program

example/bench02_zfft.f90

@@ -0,0 +1,64 @@
+program main
+use fftpack, only: zffti, zfftf, zfftb, fft, ifft
+use fftpack_kind, only: rk
+
+implicit none
+integer, parameter :: N = 1024*135*77  !> (2**10)*(3**3)*5*7*11
+
+complex(rk), dimension(N) :: x, z
+real(rk), dimension(4*N+15) :: w
+real(rk) :: err, time_i, time_f, time_b, t1, t2
+
+call random_number(x%re)
+z = x
+
+print *, "02: Benchmarking zfft & fft"
+
+call cpu_time(t1)
+call zffti(N, w)
+call cpu_time(t2)
+time_i = t2-t1
+print *, "Initializing: done"
+
+call cpu_time(t1)
+call zfftf(N, z, w)
+call cpu_time(t2)
+time_f = t2-t1
+print *, "Forward: done"
+
+call cpu_time(t1)
+call zfftb(N, z, w)
+call cpu_time(t2)
+time_b = t2-t1
+print *, "Backward: done"
+print *, ""
+
+err = maxval(abs(x-real(z/N,rk)))
+print *, "--zfft"
+print *, "Error: ", err
+print *, "Init. time: ", time_i
+print *, "Forward time: ", time_f
+print *, "Backward time: ", time_b
+print *, ""
+
+print *, "Comparing to calls through fft"
+call cpu_time(t1)
+z = fft(x)
+call cpu_time(t2)
+time_f = t2-t1
+print *, "Init. & forward: done"
+
+call cpu_time(t1)
+z = ifft(z)
+call cpu_time(t2)
+time_b = t2-t1
+print *, "Backward: done"
+print *, ""
+
+err = maxval(abs(x-real(z/N,rk)))
+print *, "--fft"
+print *, "Error: ", err
+print *, "Init. & forward time: ", time_f
+print *, "Backward time: ", time_b
+print *, ""
+end program