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Text File  |  1996-09-28  |  2KB  |  53 lines
  1.       subroutine passb4 (ido,l1,cc,ch,wa1,wa2,wa3)
  2.       implicit double precision (a-h,o-z)
  3.       dimension       cc(ido,4,l1)           ,ch(ido,l1,4)           ,
  4.      1                wa1(1)     ,wa2(1)     ,wa3(1)
  5.       if (ido .ne. 2) go to 102
  6.       do 101 k=1,l1
  7.          ti1 = cc(2,1,k)-cc(2,3,k)
  8.          ti2 = cc(2,1,k)+cc(2,3,k)
  9.          tr4 = cc(2,4,k)-cc(2,2,k)
  10.          ti3 = cc(2,2,k)+cc(2,4,k)
  11.          tr1 = cc(1,1,k)-cc(1,3,k)
  12.          tr2 = cc(1,1,k)+cc(1,3,k)
  13.          ti4 = cc(1,2,k)-cc(1,4,k)
  14.          tr3 = cc(1,2,k)+cc(1,4,k)
  15.          ch(1,k,1) = tr2+tr3
  16.          ch(1,k,3) = tr2-tr3
  17.          ch(2,k,1) = ti2+ti3
  18.          ch(2,k,3) = ti2-ti3
  19.          ch(1,k,2) = tr1+tr4
  20.          ch(1,k,4) = tr1-tr4
  21.          ch(2,k,2) = ti1+ti4
  22.          ch(2,k,4) = ti1-ti4
  23.   101 continue
  24.       return
  25.   102 do 104 k=1,l1
  26.          do 103 i=2,ido,2
  27.             ti1 = cc(i,1,k)-cc(i,3,k)
  28.             ti2 = cc(i,1,k)+cc(i,3,k)
  29.             ti3 = cc(i,2,k)+cc(i,4,k)
  30.             tr4 = cc(i,4,k)-cc(i,2,k)
  31.             tr1 = cc(i-1,1,k)-cc(i-1,3,k)
  32.             tr2 = cc(i-1,1,k)+cc(i-1,3,k)
  33.             ti4 = cc(i-1,2,k)-cc(i-1,4,k)
  34.             tr3 = cc(i-1,2,k)+cc(i-1,4,k)
  35.             ch(i-1,k,1) = tr2+tr3
  36.             cr3 = tr2-tr3
  37.             ch(i,k,1) = ti2+ti3
  38.             ci3 = ti2-ti3
  39.             cr2 = tr1+tr4
  40.             cr4 = tr1-tr4
  41.             ci2 = ti1+ti4
  42.             ci4 = ti1-ti4
  43.             ch(i-1,k,2) = wa1(i-1)*cr2-wa1(i)*ci2
  44.             ch(i,k,2) = wa1(i-1)*ci2+wa1(i)*cr2
  45.             ch(i-1,k,3) = wa2(i-1)*cr3-wa2(i)*ci3
  46.             ch(i,k,3) = wa2(i-1)*ci3+wa2(i)*cr3
  47.             ch(i-1,k,4) = wa3(i-1)*cr4-wa3(i)*ci4
  48.             ch(i,k,4) = wa3(i-1)*ci4+wa3(i)*cr4
  49.   103    continue
  50.   104 continue
  51.       return
  52.       end
  53.