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! $Header$
#include "cctk.h"
module matdet
use lapack
implicit none
private
public calc_symdet4
contains
subroutine calc_symdet4 (g4, dtg4, lerr)
CCTK_REAL, intent(in) :: g4(4,4)
CCTK_REAL, intent(out) :: dtg4
logical, optional, intent(out) :: lerr
CCTK_REAL :: tmp(4,4)
integer :: ipiv(4)
integer :: info
integer :: nperms
integer :: i
character :: msg*100
tmp = g4
call sytrf (4, 4, tmp, 4, ipiv, info)
if (info < 0) then
write (msg, '("Error in call to SYTRF, info=",i4)') info
call CCTK_WARN (1, msg)
end if
if (present(lerr)) lerr = info /= 0
if (info > 0) then
dtg4 = 0
return
end if
nperms = 0
do i=1,4
if (mod(ipiv(i),2) /= mod(i,2)) nperms = nperms+1
end do
if (mod(nperms,2) /=0) call CCTK_WARN (0, "internal error")
nperms = nperms / 2
dtg4 = 1
if (mod(nperms,2)/=0) dtg4 = -1
do i=1,4
dtg4 = dtg4 * tmp(i,i)
end do
end subroutine calc_symdet4
end module matdet
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