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c\BeginDoc
c
c\Name: zsortc
c
c\Description:
c Sorts the Complex*16 array in X into the order
c specified by WHICH and optionally applies the permutation to the
c Double precision array Y.
c
c\Usage:
c call zsortc
c ( WHICH, APPLY, N, X, Y )
c
c\Arguments
c WHICH Character*2. (Input)
c 'LM' -> sort X into increasing order of magnitude.
c 'SM' -> sort X into decreasing order of magnitude.
c 'LR' -> sort X with real(X) in increasing algebraic order
c 'SR' -> sort X with real(X) in decreasing algebraic order
c 'LI' -> sort X with imag(X) in increasing algebraic order
c 'SI' -> sort X with imag(X) in decreasing algebraic order
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 X Complex*16 array of length N. (INPUT/OUTPUT)
c This is the array to be sorted.
c
c Y Complex*16 array of length N. (INPUT/OUTPUT)
c
c\EndDoc
c
c-----------------------------------------------------------------------
c
c\BeginLib
c
c\Routines called:
c dlapy2 LAPACK routine to compute sqrt(x**2+y**2) carefully.
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 Adapted from the sort routine in LANSO.
c
c\SCCS Information: @(#)
c FILE: sortc.F SID: 2.2 DATE OF SID: 4/20/96 RELEASE: 2
c
c\EndLib
c
c-----------------------------------------------------------------------
c
subroutine zsortc (which, apply, n, x, y)
c
c %------------------%
c | Scalar Arguments |
c %------------------%
c
character*2 which
logical apply
integer n
c
c %-----------------%
c | Array Arguments |
c %-----------------%
c
Complex*16
& x(0:n-1), y(0:n-1)
c
c %---------------%
c | Local Scalars |
c %---------------%
c
integer i, igap, j
Complex*16
& temp
Double precision
& temp1, temp2
c
c %--------------------%
c | External functions |
c %--------------------%
c
Double precision
& dlapy2
c
c %--------------------%
c | Intrinsic Functions |
c %--------------------%
Intrinsic
& dble, dimag
c
c %-----------------------%
c | Executable Statements |
c %-----------------------%
c
igap = n / 2
c
if (which .eq. 'LM') then
c
c %--------------------------------------------%
c | Sort X 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(dble(x(j)),dimag(x(j)))
temp2 = dlapy2(dble(x(j+igap)),dimag(x(j+igap)))
c
if (temp1.gt.temp2) then
temp = x(j)
x(j) = x(j+igap)
x(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 X 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(dble(x(j)),dimag(x(j)))
temp2 = dlapy2(dble(x(j+igap)),dimag(x(j+igap)))
c
if (temp1.lt.temp2) then
temp = x(j)
x(j) = x(j+igap)
x(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 (dble(x(j)).gt.dble(x(j+igap))) then
temp = x(j)
x(j) = x(j+igap)
x(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 (dble(x(j)).lt.dble(x(j+igap))) then
temp = x(j)
x(j) = x(j+igap)
x(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 algebraic order |
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 (dimag(x(j)).gt.dimag(x(j+igap))) then
temp = x(j)
x(j) = x(j+igap)
x(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 algebraic order |
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 (dimag(x(j)).lt.dimag(x(j+igap))) then
temp = x(j)
x(j) = x(j+igap)
x(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 zsortc |
c %---------------%
c
end
|
