subroutine dpssf4 (ido,l1,cc,ch,wa1,wa2,wa3) double precision cc(ido,4,l1), ch(ido,l1,4), wa1(1), wa2(1), 1 wa3(1), ci2, ci3, ci4, cr2, cr3, cr4, ti1, ti2, ti3, ti4, 2 tr1, tr2, tr3, tr4 c if (ido .ne. 2) go to 102 do 101 k=1,l1 ti1 = cc(2,1,k)-cc(2,3,k) ti2 = cc(2,1,k)+cc(2,3,k) tr4 = cc(2,2,k)-cc(2,4,k) ti3 = cc(2,2,k)+cc(2,4,k) tr1 = cc(1,1,k)-cc(1,3,k) tr2 = cc(1,1,k)+cc(1,3,k) ti4 = cc(1,4,k)-cc(1,2,k) tr3 = cc(1,2,k)+cc(1,4,k) ch(1,k,1) = tr2+tr3 ch(1,k,3) = tr2-tr3 ch(2,k,1) = ti2+ti3 ch(2,k,3) = ti2-ti3 ch(1,k,2) = tr1+tr4 ch(1,k,4) = tr1-tr4 ch(2,k,2) = ti1+ti4 ch(2,k,4) = ti1-ti4 101 continue return c 102 do 104 k=1,l1 do 103 i=2,ido,2 ti1 = cc(i,1,k)-cc(i,3,k) ti2 = cc(i,1,k)+cc(i,3,k) ti3 = cc(i,2,k)+cc(i,4,k) tr4 = cc(i,2,k)-cc(i,4,k) tr1 = cc(i-1,1,k)-cc(i-1,3,k) tr2 = cc(i-1,1,k)+cc(i-1,3,k) ti4 = cc(i-1,4,k)-cc(i-1,2,k) tr3 = cc(i-1,2,k)+cc(i-1,4,k) ch(i-1,k,1) = tr2+tr3 cr3 = tr2-tr3 ch(i,k,1) = ti2+ti3 ci3 = ti2-ti3 cr2 = tr1+tr4 cr4 = tr1-tr4 ci2 = ti1+ti4 ci4 = ti1-ti4 ch(i-1,k,2) = wa1(i-1)*cr2+wa1(i)*ci2 ch(i,k,2) = wa1(i-1)*ci2-wa1(i)*cr2 ch(i-1,k,3) = wa2(i-1)*cr3+wa2(i)*ci3 ch(i,k,3) = wa2(i-1)*ci3-wa2(i)*cr3 ch(i-1,k,4) = wa3(i-1)*cr4+wa3(i)*ci4 ch(i,k,4) = wa3(i-1)*ci4-wa3(i)*cr4 103 continue 104 continue c return end