da_find_fft_trig_funcs.inc

1 subroutine da_find_fft_trig_funcs(n, trig_functs)
2 
3    !---------------------------------------------------------------------------
4    ! Purpose: Set up constants required for Fourier, sine and cosine transforms
5    !---------------------------------------------------------------------------
6 
7    implicit none
8 
9    integer, intent(in)  :: n
10    real,    intent(out) :: trig_functs(:)
11 
12    integer :: k, nil, nhl
13    real    :: del, angle
14 
15    ! in da_control
16    ! if (trace_use) call da_trace_entry("da_find_fft_trig_funcs")
17 
18    !---------------------------------------------------------------------------
19    ! [1.0] Trig functions for real periodic transform:
20    !---------------------------------------------------------------------------
21 
22    trig_functs(:) = 0.0
23 
24    del=4.0*(pi/2.0)/float(n)
25    nil=0
26    nhl=(n/2)-1
27 
28    do k=nil,nhl
29       angle=float(k)*del
30       trig_functs(2*k+1)=cos(angle)
31       trig_functs(2*k+2)=sin(angle)
32    end do
33 
34    ! [1.1] extra trig functions for cosine transform:
35 
36    del=0.5*del
37    do k=1,nhl
38       angle=float(k)*del
39       trig_functs(2*n+k)=sin(angle)
40    end do
41   
42    ! [1.2] extra trig functions for shifted cosine transform:
43 
44    del=0.5*del
45    do k=1,n
46       angle=float(k)*del
47       trig_functs(n+k)=sin(angle)
48    end do
49 
50    !if (trace_use) call da_trace_exit("da_find_fft_trig_funcs")
51 
52 end subroutine da_find_fft_trig_funcs
53 
54