c-----------------------------------------------------------------------
c\BeginDoc
c
c\Name: dsortc
c
c\Description:
c Sorts the complex array in XREAL and XIMAG into the order
c specified by WHICH and optionally applies the permutation to the
c real array Y. It is assumed that if an element of XIMAG is
c nonzero, then its negative is also an element. In other words,
c both members of a complex conjugate pair are to be sorted and the
c pairs are kept adjacent to each other.
c
c\Usage:
c call dsortc
c ( WHICH, APPLY, N, XREAL, XIMAG, Y )
c
c\Arguments
c WHICH Character*2. (Input)
c 'LM' -> sort XREAL,XIMAG into increasing order of magnitude.
c 'SM' -> sort XREAL,XIMAG into decreasing order of magnitude.
c 'LR' -> sort XREAL into increasing order of algebraic.
c 'SR' -> sort XREAL into decreasing order of algebraic.
c 'LI' -> sort XIMAG into increasing order of magnitude.
c 'SI' -> sort XIMAG into decreasing order of magnitude.
c NOTE: If an element of XIMAG is non-zero, then its negative
c is also an element.
c
c APPLY Logical. (Input)
c APPLY = .TRUE. -> apply the sorted order to array Y.
c APPLY = .FALSE. -> do not apply the sorted order to array Y.
c
c N Integer. (INPUT)
c Size of the arrays.
c
c XREAL, Double precision array of length N. (INPUT/OUTPUT)
c XIMAG Real and imaginary part of the array to be sorted.
c
c Y Double precision array of length N. (INPUT/OUTPUT)
c
c\EndDoc
c
c-----------------------------------------------------------------------
c
c\BeginLib
c
c\Author
c Danny Sorensen Phuong Vu
c Richard Lehoucq CRPC / Rice University
c Dept. of Computational & Houston, Texas
c Applied Mathematics
c Rice University
c Houston, Texas
c
c\Revision history:
c xx/xx/92: Version ' 2.1'
c Adapted from the sort routine in LANSO.
c
c\SCCS Information: @(#)
c FILE: sortc.F SID: 2.3 DATE OF SID: 4/20/96 RELEASE: 2
c
c\EndLib
c
c-----------------------------------------------------------------------
c
subroutine dsortc (which, apply, n, xreal, ximag, y)
c
c %------------------%
c | Scalar Arguments |
c %------------------%
c
character*2 which
logical apply
integer n
c
c %-----------------%
c | Array Arguments |
c %-----------------%
c
Double precision
& xreal(0:n-1), ximag(0:n-1), y(0:n-1)
c
c %---------------%
c | Local Scalars |
c %---------------%
c
integer i, igap, j
Double precision
& temp, temp1, temp2
c
c %--------------------%
c | External Functions |
c %--------------------%
c
Double precision
& dlapy2
external dlapy2
c
c %-----------------------%
c | Executable Statements |
c %-----------------------%
c
igap = n / 2
c
if (which .eq. 'LM') then
c
c %------------------------------------------------------%
c | Sort XREAL,XIMAG into increasing order of magnitude. |
c %------------------------------------------------------%
c
10 continue
if (igap .eq. 0) go to 9000
c
do 30 i = igap, n-1
j = i-igap
20 continue
c
if (j.lt.0) go to 30
c
temp1 = dlapy2(xreal(j),ximag(j))
temp2 = dlapy2(xreal(j+igap),ximag(j+igap))
c
if (temp1.gt.temp2) then
temp = xreal(j)
xreal(j) = xreal(j+igap)
xreal(j+igap) = temp
c
temp = ximag(j)
ximag(j) = ximag(j+igap)
ximag(j+igap) = temp
c
if (apply) then
temp = y(j)
y(j) = y(j+igap)
y(j+igap) = temp
end if
else
go to 30
end if
j = j-igap
go to 20
30 continue
igap = igap / 2
go to 10
c
else if (which .eq. 'SM') then
c
c %------------------------------------------------------%
c | Sort XREAL,XIMAG into decreasing order of magnitude. |
c %------------------------------------------------------%
c
40 continue
if (igap .eq. 0) go to 9000
c
do 60 i = igap, n-1
j = i-igap
50 continue
c
if (j .lt. 0) go to 60
c
temp1 = dlapy2(xreal(j),ximag(j))
temp2 = dlapy2(xreal(j+igap),ximag(j+igap))
c
if (temp1.lt.temp2) then
temp = xreal(j)
xreal(j) = xreal(j+igap)
xreal(j+igap) = temp
c
temp = ximag(j)
ximag(j) = ximag(j+igap)
ximag(j+igap) = temp
c
if (apply) then
temp = y(j)
y(j) = y(j+igap)
y(j+igap) = temp
end if
else
go to 60
endif
j = j-igap
go to 50
60 continue
igap = igap / 2
go to 40
c
else if (which .eq. 'LR') then
c
c %------------------------------------------------%
c | Sort XREAL into increasing order of algebraic. |
c %------------------------------------------------%
c
70 continue
if (igap .eq. 0) go to 9000
c
do 90 i = igap, n-1
j = i-igap
80 continue
c
if (j.lt.0) go to 90
c
if (xreal(j).gt.xreal(j+igap)) then
temp = xreal(j)
xreal(j) = xreal(j+igap)
xreal(j+igap) = temp
c
temp = ximag(j)
ximag(j) = ximag(j+igap)
ximag(j+igap) = temp
c
if (apply) then
temp = y(j)
y(j) = y(j+igap)
y(j+igap) = temp
end if
else
go to 90
endif
j = j-igap
go to 80
90 continue
igap = igap / 2
go to 70
c
else if (which .eq. 'SR') then
c
c %------------------------------------------------%
c | Sort XREAL into decreasing order of algebraic. |
c %------------------------------------------------%
c
100 continue
if (igap .eq. 0) go to 9000
do 120 i = igap, n-1
j = i-igap
110 continue
c
if (j.lt.0) go to 120
c
if (xreal(j).lt.xreal(j+igap)) then
temp = xreal(j)
xreal(j) = xreal(j+igap)
xreal(j+igap) = temp
c
temp = ximag(j)
ximag(j) = ximag(j+igap)
ximag(j+igap) = temp
c
if (apply) then
temp = y(j)
y(j) = y(j+igap)
y(j+igap) = temp
end if
else
go to 120
endif
j = j-igap
go to 110
120 continue
igap = igap / 2
go to 100
c
else if (which .eq. 'LI') then
c
c %------------------------------------------------%
c | Sort XIMAG into increasing order of magnitude. |
c %------------------------------------------------%
c
130 continue
if (igap .eq. 0) go to 9000
do 150 i = igap, n-1
j = i-igap
140 continue
c
if (j.lt.0) go to 150
c
if (abs(ximag(j)).gt.abs(ximag(j+igap))) then
temp = xreal(j)
xreal(j) = xreal(j+igap)
xreal(j+igap) = temp
c
temp = ximag(j)
ximag(j) = ximag(j+igap)
ximag(j+igap) = temp
c
if (apply) then
temp = y(j)
y(j) = y(j+igap)
y(j+igap) = temp
end if
else
go to 150
endif
j = j-igap
go to 140
150 continue
igap = igap / 2
go to 130
c
else if (which .eq. 'SI') then
c
c %------------------------------------------------%
c | Sort XIMAG into decreasing order of magnitude. |
c %------------------------------------------------%
c
160 continue
if (igap .eq. 0) go to 9000
do 180 i = igap, n-1
j = i-igap
170 continue
c
if (j.lt.0) go to 180
c
if (abs(ximag(j)).lt.abs(ximag(j+igap))) then
temp = xreal(j)
xreal(j) = xreal(j+igap)
xreal(j+igap) = temp
c
temp = ximag(j)
ximag(j) = ximag(j+igap)
ximag(j+igap) = temp
c
if (apply) then
temp = y(j)
y(j) = y(j+igap)
y(j+igap) = temp
end if
else
go to 180
endif
j = j-igap
go to 170
180 continue
igap = igap / 2
go to 160
end if
c
9000 continue
return
c
c %---------------%
c | End of dsortc |
c %---------------%
c
end
