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subroutines.f90
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subroutines.f90
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!General numerical routines and global accuracy. Includes modified dverk for CAMB.
!cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
subroutine splder(y,dy,n, g)
use Precision
! Splder fits a cubic spline to y and returns the first derivatives at
! the grid points in dy. Dy is equivalent to a 4th-order Pade
! difference formula for dy/di.
implicit none
integer, intent(in) :: n
real(dl), intent(in) :: y(n),g(n)
real(dl), intent(out) :: dy(n)
integer :: n1, i
real(dl), allocatable, dimension(:) :: f
allocate(f(n))
n1=n-1
! Quartic fit to dy/di at boundaries, assuming d3y/di3=0.
f(1)=(-10._dl*y(1)+15._dl*y(2)-6._dl*y(3)+y(4))/6._dl
f(n)=(10._dl*y(n)-15._dl*y(n1)+6._dl*y(n-2)-y(n-3))/6._dl
! Solve the tridiagonal system
! dy(i-1)+4*dy(i)+dy(i+1)=3*(y(i+1)-y(i-1)), i=2,3,...,n1,
! with dy(1)=f(1), dy(n)=f(n).
do i=2,n1
f(i)=g(i)*(3._dl*(y(i+1)-y(i-1))-f(i-1))
end do
dy(n)=f(n)
do i=n1,1,-1
dy(i)=f(i)-g(i)*dy(i+1)
end do
deallocate(f)
end subroutine splder
!ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
subroutine splini(g,n)
use Precision
! Splini must be called before splder to initialize array g in common.
implicit none
integer, intent(in) :: n
real(dl), intent(out):: g(n)
integer :: i
g(1)=0._dl
do i=2,n
g(i)=1/(4._dl-g(i-1))
end do
end subroutine splini
!cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
function rombint2(f,a,b,tol, maxit, minsteps)
use precision
! Rombint returns the integral from a to b of using Romberg integration.
! The method converges provided that f(x) is continuous in (a,b).
! f must be real(dl) and must be declared external in the calling
! routine. tol indicates the desired relative accuracy in the integral.
! Modified by AL to specify max iterations and minimum number of steps
! (min steps useful to stop wrong results on periodic or sharp functions)
implicit none
integer, parameter :: MAXITER=20,MAXJ=5
dimension g(MAXJ+1)
real(dl) f
external f
real(dl) :: rombint2
real(dl), intent(in) :: a,b,tol
integer, intent(in):: maxit,minsteps
integer :: nint, i, k, jmax, j
real(dl) :: h, gmax, error, g, g0, g1, fourj
h=0.5d0*(b-a)
gmax=h*(f(a)+f(b))
g(1)=gmax
nint=1
error=1.0d20
i=0
do
i=i+1
if (i > maxit.or.(i > 5.and.abs(error) < tol) .and. nint > minsteps) exit
! Calculate next trapezoidal rule approximation to integral.
g0=0._dl
do k=1,nint
g0=g0+f(a+(k+k-1)*h)
end do
g0=0.5d0*g(1)+h*g0
h=0.5d0*h
nint=nint+nint
jmax=min(i,MAXJ)
fourj=1._dl
do j=1,jmax
! Use Richardson extrapolation.
fourj=4._dl*fourj
g1=g0+(g0-g(j))/(fourj-1._dl)
g(j)=g0
g0=g1
end do
if (abs(g0).gt.tol) then
error=1._dl-gmax/g0
else
error=gmax
end if
gmax=g0
g(jmax+1)=g0
end do
rombint2=g0
if (i > maxit .and. abs(error) > tol) then
write(*,*) 'Warning: Rombint2 failed to converge; '
write (*,*)'integral, error, tol:', rombint2,error, tol
end if
end function rombint2
!cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
function rombint(f,a,b,tol)
use Precision
! Rombint returns the integral from a to b of using Romberg integration.
! The method converges provided that f(x) is continuous in (a,b).
! f must be real(dl) and must be declared external in the calling
! routine. tol indicates the desired relative accuracy in the integral.
!
implicit none
integer, parameter :: MAXITER=20
integer, parameter :: MAXJ=5
dimension g(MAXJ+1)
real(dl) f
external f
real(dl) :: rombint
real(dl), intent(in) :: a,b,tol
integer :: nint, i, k, jmax, j
real(dl) :: h, gmax, error, g, g0, g1, fourj
!
h=0.5d0*(b-a)
gmax=h*(f(a)+f(b))
g(1)=gmax
nint=1
error=1.0d20
i=0
10 i=i+1
if (i.gt.MAXITER.or.(i.gt.5.and.abs(error).lt.tol)) &
go to 40
! Calculate next trapezoidal rule approximation to integral.
g0=0._dl
do 20 k=1,nint
g0=g0+f(a+(k+k-1)*h)
20 continue
g0=0.5d0*g(1)+h*g0
h=0.5d0*h
nint=nint+nint
jmax=min(i,MAXJ)
fourj=1._dl
do 30 j=1,jmax
! Use Richardson extrapolation.
fourj=4._dl*fourj
g1=g0+(g0-g(j))/(fourj-1._dl)
g(j)=g0
g0=g1
30 continue
if (abs(g0).gt.tol) then
error=1._dl-gmax/g0
else
error=gmax
end if
gmax=g0
g(jmax+1)=g0
go to 10
40 rombint=g0
if (i.gt.MAXITER.and.abs(error).gt.tol) then
write(*,*) 'Warning: Rombint failed to converge; '
write (*,*)'integral, error, tol:', rombint,error, tol
end if
end function rombint
!cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
function rombint_obj(obj,f,a,b,tol, maxit)
use Precision
! Rombint returns the integral from a to b of using Romberg integration.
! The method converges provided that f(x) is continuous in (a,b).
! f must be real(dl) and must be declared external in the calling
! routine. tol indicates the desired relative accuracy in the integral.
!
implicit none
integer, intent(in), optional :: maxit
integer :: MAXITER=20
integer, parameter :: MAXJ=5
dimension g(MAXJ+1)
real obj !dummy
real(dl) f
external f
real(dl) :: rombint_obj
real(dl), intent(in) :: a,b,tol
integer :: nint, i, k, jmax, j
real(dl) :: h, gmax, error, g, g0, g1, fourj
!
if (present(maxit)) then
MaxIter = maxit
end if
h=0.5d0*(b-a)
gmax=h*(f(obj,a)+f(obj,b))
g(1)=gmax
nint=1
error=1.0d20
i=0
10 i=i+1
if (i.gt.MAXITER.or.(i.gt.5.and.abs(error).lt.tol)) &
go to 40
! Calculate next trapezoidal rule approximation to integral.
g0=0._dl
do 20 k=1,nint
g0=g0+f(obj,a+(k+k-1)*h)
20 continue
g0=0.5d0*g(1)+h*g0
h=0.5d0*h
nint=nint+nint
jmax=min(i,MAXJ)
fourj=1._dl
do 30 j=1,jmax
! Use Richardson extrapolation.
fourj=4._dl*fourj
g1=g0+(g0-g(j))/(fourj-1._dl)
g(j)=g0
g0=g1
30 continue
if (abs(g0).gt.tol) then
error=1._dl-gmax/g0
else
error=gmax
end if
gmax=g0
g(jmax+1)=g0
go to 10
40 rombint_obj=g0
if (i.gt.MAXITER.and.abs(error).gt.tol) then
write(*,*) 'Warning: Rombint failed to converge; '
write (*,*)'integral, error, tol:', rombint_obj,error, tol
end if
end function rombint_obj
!cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
! calculates array of second derivatives used by cubic spline
! interpolation. y2 is array of second derivatives, yp1 and ypn are first
! derivatives at end points.
!Thanks Martin Reinecke
subroutine spline(x,y,n,d11,d1n,d2)
use Precision
integer, intent(in) :: n
real(dl), intent(in) :: x(n), y(n), d11, d1n
real(dl), intent(out) :: d2(n)
integer i
real(dl) xp,qn,sig,un,xxdiv,u(n-1),d1l,d1r
d1r= (y(2)-y(1))/(x(2)-x(1))
if (d11>.99e30_dl) then
d2(1)=0._dl
u(1)=0._dl
else
d2(1)=-0.5_dl
u(1)=(3._dl/(x(2)-x(1)))*(d1r-d11)
endif
do i=2,n-1
d1l=d1r
d1r=(y(i+1)-y(i))/(x(i+1)-x(i))
xxdiv=1._dl/(x(i+1)-x(i-1))
sig=(x(i)-x(i-1))*xxdiv
xp=1._dl/(sig*d2(i-1)+2._dl)
d2(i)=(sig-1._dl)*xp
u(i)=(6._dl*(d1r-d1l)*xxdiv-sig*u(i-1))*xp
end do
d1l=d1r
if (d1n>.99e30_dl) then
qn=0._dl
un=0._dl
else
qn=0.5_dl
un=(3._dl/(x(n)-x(n-1)))*(d1n-d1l)
endif
d2(n)=(un-qn*u(n-1))/(qn*d2(n-1)+1._dl)
do i=n-1,1,-1
d2(i)=d2(i)*d2(i+1)+u(i)
end do
end subroutine spline
SUBROUTINE spline_deriv(x,y,y2,y1,n)
!Get derivative y1 given array of x, y and y''
use Precision
implicit none
INTEGER, intent(in) :: n
real(dl), intent(in) :: x(n), y(n), y2(n)
real(dl), intent(out) :: y1(n)
INTEGER i
real(dl) dx
do i=1, n-1
dx = (x(i+1) - x(i))
y1(i) = (y(i+1) - y(i))/dx - dx*(2*y2(i) + y2(i+1))/6
end do
dx = x(n) - x(n-1)
y1(n) = (y(n) - y(n-1))/dx + dx* ( y2(i-1) + 2*y2(i) )/6
END SUBROUTINE spline_deriv
subroutine spline_integrate(x,y,y2,yint,n)
!Cumulative integral of cubic spline
use Precision
integer, intent(in) :: n
real(dl), intent(in) :: x(n), y(n), y2(n)
real(dl), intent(out) :: yint(n)
real(dl) dx
integer i
yint(1) = 0
do i=2, n
dx = (x(i) - x(i-1))
yint(i) = yint(i-1) + dx*( (y(i)+y(i-1))/2 - dx**2/24*(y2(i)+y2(i-1)))
end do
end subroutine spline_integrate
!ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
! this is not the splint given in numerical recipes
subroutine splint(y,z,n)
use Precision
! Splint integrates a cubic spline, providing the output value
! z = integral from 1 to n of s(i)di, where s(i) is the spline fit
! to y(i).
!
implicit none
integer, intent(in) :: n
real(dl), intent(in) :: y(n)
real(dl), intent(out) :: z
integer :: n1
real(dl) :: dy1, dyn
!
n1=n-1
! Cubic fit to dy/di at boundaries.
! dy1=(-11._dl*y(1)+18._dl*y(2)-9._dl*y(3)+2._dl*y(4))/6._dl
dy1=0._dl
dyn=(11._dl*y(n)-18._dl*y(n1)+9._dl*y(n-2)-2._dl*y(n-3))/6._dl
!
z=0.5d0*(y(1)+y(n))+(dy1-dyn)/12._dl
z= z + sum(y(2:n1))
end subroutine splint
!This version is modified to pass an object parameter to the function on each call
!Fortunately Fortran doesn't do type checking on functions, so we can pretend the
!passed object parameter (EV) is any type we like. In reality it is just a pointer.
subroutine dverk (EV,n, fcn, x, y, xend, tol, ind, c, nw, w)
use Precision
use AMLUtils
integer n, ind, nw, k
real(dl) x, y(n), xend, tol, c(*), w(nw,9), temp
real EV !It isn't, but as long as it maintains it as a pointer we are OK
! class(*) EV !seems to be correct way to do this in Fortran 2003
!
!***********************************************************************
! *
! note added 11/14/85. *
! *
! if you discover any errors in this subroutine, please contact *
! *
! kenneth r. jackson *
! department of computer science *
! university of toronto *
! toronto, ontario, *
! canada m5s 1a4 *
! *
! phone: 416-978-7075 *
! *
! electronic mail: *
! uucp: {cornell,decvax,ihnp4,linus,uw-beaver}!utcsri!krj *
! csnet: krj@toronto *
! arpa: krj.toronto@csnet-relay *
! bitnet: krj%[email protected] *
! *
! dverk is written in fortran 66. *
! *
! the constants dwarf and rreb -- c(10) and c(11), respectively -- are *
! set for a vax in double precision. they should be reset, as *
! described below, if this program is run on another machine. *
! *
! the c array is declared in this subroutine to have one element only, *
! although more elements are referenced in this subroutine. this *
! causes some compilers to issue warning messages. there is, though, *
! no error provided c is declared sufficiently large in the calling *
! program, as described below. *
! *
! the following external statement for fcn was added to avoid a *
! warning message from the unix f77 compiler. the original dverk *
! comments and code follow it. *
! *
!***********************************************************************
!
external fcn
!
!***********************************************************************
! *
! purpose - this is a runge-kutta subroutine based on verner's *
! fifth and sixth order pair of formulas for finding approximations to *
! the solution of a system of first order ordinary differential *
! equations with initial conditions. it attempts to keep the global *
! error proportional to a tolerance specified by the user. (the *
! proportionality depends on the kind of error control that is used, *
! as well as the differential equation and the range of integration.) *
! *
! various options are available to the user, including different *
! kinds of error control, restrictions on step sizes, and interrupts *
! which permit the user to examine the state of the calculation (and *
! perhaps make modifications) during intermediate stages. *
! *
! the program is efficient for non-stiff systems. however, a good *
! variable-order-adams method will probably be more efficient if the *
! function evaluations are very costly. such a method would also be *
! more suitable if one wanted to obtain a large number of intermediate *
! solution values by interpolation, as might be the case for example *
! with graphical output. *
! *
! hull-enright-jackson 1/10/76 *
! *
!***********************************************************************
! *
! use - the user must specify each of the following *
! *
! n number of equations *
! *
! fcn name of subroutine for evaluating functions - the subroutine *
! itself must also be provided by the user - it should be of *
! the following form *
! subroutine fcn(n, x, y, yprime) *
! integer n *
! real(dl) x, y(n), yprime(n) *
! *** etc *** *
! and it should evaluate yprime, given n, x and y *
! *
! x independent variable - initial value supplied by user *
! *
! y dependent variable - initial values of components y(1), y(2), *
! ..., y(n) supplied by user *
! *
! xend value of x to which integration is to be carried out - it may *
! be less than the initial value of x *
! *
! tol tolerance - the subroutine attempts to control a norm of the *
! local error in such a way that the global error is *
! proportional to tol. in some problems there will be enough *
! damping of errors, as well as some cancellation, so that *
! the global error will be less than tol. alternatively, the *
! control can be viewed as attempting to provide a *
! calculated value of y at xend which is the exact solution *
! to the problem y' = f(x,y) + e(x) where the norm of e(x) *
! is proportional to tol. (the norm is a max norm with *
! weights that depend on the error control strategy chosen *
! by the user. the default weight for the k-th component is *
! 1/max(1,abs(y(k))), which therefore provides a mixture of *
! absolute and relative error control.) *
! *
! ind indicator - on initial entry ind must be set equal to either *
! 1 or 2. if the user does not wish to use any options, he *
! should set ind to 1 - all that remains for the user to do *
! then is to declare c and w, and to specify nw. the user *
! may also select various options on initial entry by *
! setting ind = 2 and initializing the first 9 components of *
! c as described in the next section. he may also re-enter *
! the subroutine with ind = 3 as mentioned again below. in *
! any event, the subroutine returns with ind equal to *
! 3 after a normal return *
! 4, 5, or 6 after an interrupt (see options c(8), c(9)) *
! -1, -2, or -3 after an error condition (see below) *
! *
! c communications vector - the dimension must be greater than or *
! equal to 24, unless option c(1) = 4 or 5 is used, in which *
! case the dimension must be greater than or equal to n+30 *
! *
! nw first dimension of workspace w - must be greater than or *
! equal to n *
! *
! w workspace matrix - first dimension must be nw and second must *
! be greater than or equal to 9 *
! *
! the subroutine will normally return with ind = 3, having *
! replaced the initial values of x and y with, respectively, the value *
! of xend and an approximation to y at xend. the subroutine can be *
! called repeatedly with new values of xend without having to change *
! any other argument. however, changes in tol, or any of the options *
! described below, may also be made on such a re-entry if desired. *
! *
! three error returns are also possible, in which case x and y *
! will be the most recently accepted values - *
! with ind = -3 the subroutine was unable to satisfy the error *
! requirement with a particular step-size that is less than or *
! equal to hmin, which may mean that tol is too small *
! with ind = -2 the value of hmin is greater than hmax, which *
! probably means that the requested tol (which is used in the *
! calculation of hmin) is too small *
! with ind = -1 the allowed maximum number of fcn evaluations has *
! been exceeded, but this can only occur if option c(7), as *
! described in the next section, has been used *
! *
! there are several circumstances that will cause the calculations *
! to be terminated, along with output of information that will help *
! the user determine the cause of the trouble. these circumstances *
! involve entry with illegal or inconsistent values of the arguments, *
! such as attempting a normal re-entry without first changing the *
! value of xend, or attempting to re-enter with ind less than zero. *
! *
!***********************************************************************
! *
! options - if the subroutine is entered with ind = 1, the first 9 *
! components of the communications vector are initialized to zero, and *
! the subroutine uses only default values for each option. if the *
! subroutine is entered with ind = 2, the user must specify each of *
! these 9 components - normally he would first set them all to zero, *
! and then make non-zero those that correspond to the particular *
! options he wishes to select. in any event, options may be changed on *
! re-entry to the subroutine - but if the user changes any of the *
! options, or tol, in the course of a calculation he should be careful *
! about how such changes affect the subroutine - it may be better to *
! restart with ind = 1 or 2. (components 10 to 24 of c are used by the *
! program - the information is available to the user, but should not *
! normally be changed by him.) *
! *
! c(1) error control indicator - the norm of the local error is the *
! max norm of the weighted error estimate vector, the *
! weights being determined according to the value of c(1) - *
! if c(1)=1 the weights are 1 (absolute error control) *
! if c(1)=2 the weights are 1/abs(y(k)) (relative error *
! control) *
! if c(1)=3 the weights are 1/max(abs(c(2)),abs(y(k))) *
! (relative error control, unless abs(y(k)) is less *
! than the floor value, abs(c(2)) ) *
! if c(1)=4 the weights are 1/max(abs(c(k+30)),abs(y(k))) *
! (here individual floor values are used) *
! if c(1)=5 the weights are 1/abs(c(k+30)) *
! for all other values of c(1), including c(1) = 0, the *
! default values of the weights are taken to be *
! 1/max(1,abs(y(k))), as mentioned earlier *
! (in the two cases c(1) = 4 or 5 the user must declare the *
! dimension of c to be at least n+30 and must initialize the *
! components c(31), c(32), ..., c(n+30).) *
! *
! c(2) floor value - used when the indicator c(1) has the value 3 *
! *
! c(3) hmin specification - if not zero, the subroutine chooses hmin *
! to be abs(c(3)) - otherwise it uses the default value *
! 10*max(dwarf,rreb*max(weighted norm y/tol,abs(x))), *
! where dwarf is a very small positive machine number and *
! rreb is the relative roundoff error bound *
! *
! c(4) hstart specification - if not zero, the subroutine will use *
! an initial hmag equal to abs(c(4)), except of course for *
! the restrictions imposed by hmin and hmax - otherwise it *
! uses the default value of hmax*(tol)**(1/6) *
! *
! c(5) scale specification - this is intended to be a measure of the *
! scale of the problem - larger values of scale tend to make *
! the method more reliable, first by possibly restricting *
! hmax (as described below) and second, by tightening the *
! acceptance requirement - if c(5) is zero, a default value *
! of 1 is used. for linear homogeneous problems with *
! constant coefficients, an appropriate value for scale is a *
! norm of the associated matrix. for other problems, an *
! approximation to an average value of a norm of the *
! jacobian along the trajectory may be appropriate *
! *
! c(6) hmax specification - four cases are possible *
! if c(6).ne.0 and c(5).ne.0, hmax is taken to be *
! min(abs(c(6)),2/abs(c(5))) *
! if c(6).ne.0 and c(5).eq.0, hmax is taken to be abs(c(6)) *
! if c(6).eq.0 and c(5).ne.0, hmax is taken to be *
! 2/abs(c(5)) *
! if c(6).eq.0 and c(5).eq.0, hmax is given a default value *
! of 2 *
! *
! c(7) maximum number of function evaluations - if not zero, an *
! error return with ind = -1 will be caused when the number *
! of function evaluations exceeds abs(c(7)) *
! *
! c(8) interrupt number 1 - if not zero, the subroutine will *
! interrupt the calculations after it has chosen its *
! preliminary value of hmag, and just before choosing htrial *
! and xtrial in preparation for taking a step (htrial may *
! differ from hmag in sign, and may require adjustment if *
! xend is near) - the subroutine returns with ind = 4, and *
! will resume calculation at the point of interruption if *
! re-entered with ind = 4 *
! *
! c(9) interrupt number 2 - if not zero, the subroutine will *
! interrupt the calculations immediately after it has *
! decided whether or not to accept the result of the most *
! recent trial step, with ind = 5 if it plans to accept, or *
! ind = 6 if it plans to reject - y(*) is the previously *
! accepted result, while w(*,9) is the newly computed trial *
! value, and w(*,2) is the unweighted error estimate vector. *
! the subroutine will resume calculations at the point of *
! interruption on re-entry with ind = 5 or 6. (the user may *
! change ind in this case if he wishes, for example to force *
! acceptance of a step that would otherwise be rejected, or *
! vice versa. he can also restart with ind = 1 or 2.) *
! *
!***********************************************************************
! *
! summary of the components of the communications vector *
! *
! prescribed at the option determined by the program *
! of the user *
! *
! c(10) rreb(rel roundoff err bnd) *
! c(1) error control indicator c(11) dwarf (very small mach no) *
! c(2) floor value c(12) weighted norm y *
! c(3) hmin specification c(13) hmin *
! c(4) hstart specification c(14) hmag *
! c(5) scale specification c(15) scale *
! c(6) hmax specification c(16) hmax *
! c(7) max no of fcn evals c(17) xtrial *
! c(8) interrupt no 1 c(18) htrial *
! c(9) interrupt no 2 c(19) est *
! c(20) previous xend *
! c(21) flag for xend *
! c(22) no of successful steps *
! c(23) no of successive failures *
! c(24) no of fcn evals *
! *
! if c(1) = 4 or 5, c(31), c(32), ... c(n+30) are floor values *
! *
!***********************************************************************
! *
! an overview of the program *
! *
! begin initialization, parameter checking, interrupt re-entries *
! ......abort if ind out of range 1 to 6 *
! . cases - initial entry, normal re-entry, interrupt re-entries *
! . case 1 - initial entry (ind .eq. 1 or 2) *
! v........abort if n.gt.nw or tol.le.0 *
! . if initial entry without options (ind .eq. 1) *
! . set c(1) to c(9) equal to zero *
! . else initial entry with options (ind .eq. 2) *
! . make c(1) to c(9) non-negative *
! . make floor values non-negative if they are to be used *
! . end if *
! . initialize rreb, dwarf, prev xend, flag, counts *
! . case 2 - normal re-entry (ind .eq. 3) *
! .........abort if xend reached, and either x changed or xend not *
! . re-initialize flag *
! . case 3 - re-entry following an interrupt (ind .eq. 4 to 6) *
! v transfer control to the appropriate re-entry point....... *
! . end cases . *
! . end initialization, etc. . *
! . v *
! . loop through the following 4 stages, once for each trial step . *
! . stage 1 - prepare . *
!***********error return (with ind=-1) if no of fcn evals too great . *
! . calc slope (adding 1 to no of fcn evals) if ind .ne. 6 . *
! . calc hmin, scale, hmax . *
!***********error return (with ind=-2) if hmin .gt. hmax . *
! . calc preliminary hmag . *
!***********interrupt no 1 (with ind=4) if requested.......re-entry.v *
! . calc hmag, xtrial and htrial . *
! . end stage 1 . *
! v stage 2 - calc ytrial (adding 7 to no of fcn evals) . *
! . stage 3 - calc the error estimate . *
! . stage 4 - make decisions . *
! . set ind=5 if step acceptable, else set ind=6 . *
!***********interrupt no 2 if requested....................re-entry.v *
! . if step accepted (ind .eq. 5) *
! . update x, y from xtrial, ytrial *
! . add 1 to no of successful steps *
! . set no of successive failures to zero *
!**************return(with ind=3, xend saved, flag set) if x .eq. xend *
! . else step not accepted (ind .eq. 6) *
! . add 1 to no of successive failures *
!**************error return (with ind=-3) if hmag .le. hmin *
! . end if *
! . end stage 4 *
! . end loop *
! . *
! begin abort action *
! output appropriate message about stopping the calculations, *
! along with values of ind, n, nw, tol, hmin, hmax, x, xend, *
! previous xend, no of successful steps, no of successive *
! failures, no of fcn evals, and the components of y *
! stop *
! end abort action *
! *
!***********************************************************************
!
! ******************************************************************
! * begin initialization, parameter checking, interrupt re-entries *
! ******************************************************************
!
! ......abort if ind out of range 1 to 6
if (ind.lt.1 .or. ind.gt.6) go to 500
!
! cases - initial entry, normal re-entry, interrupt re-entries
! go to (5, 5, 45, 1111, 2222, 2222), ind
if (ind==3) goto 45
if (ind==4) goto 1111
if (ind==5 .or. ind==6) goto 2222
! case 1 - initial entry (ind .eq. 1 or 2)
! .........abort if n.gt.nw or tol.le.0
if (n.gt.nw .or. tol.le.0._dl) go to 500
if (ind.eq. 2) go to 15
! initial entry without options (ind .eq. 1)
! set c(1) to c(9) equal to 0
do k = 1, 9
c(k) = 0._dl
end do
go to 35
15 continue
! initial entry with options (ind .eq. 2)
! make c(1) to c(9) non-negative
do k = 1, 9
c(k) = dabs(c(k))
end do
! make floor values non-negative if they are to be used
if (c(1).ne.4._dl .and. c(1).ne.5._dl) go to 30
do k = 1, n
c(k+30) = dabs(c(k+30))
end do
30 continue
35 continue
! initialize rreb, dwarf, prev xend, flag, counts
c(10) = 2._dl**(-56)
c(11) = 1.d-35
! set previous xend initially to initial value of x
c(20) = x
do k = 21, 24
c(k) = 0._dl
end do
go to 50
! case 2 - normal re-entry (ind .eq. 3)
! .........abort if xend reached, and either x changed or xend not
45 if (c(21).ne.0._dl .and. &
(x.ne.c(20) .or. xend.eq.c(20))) go to 500
! re-initialize flag
c(21) = 0._dl
go to 50
! case 3 - re-entry following an interrupt (ind .eq. 4 to 6)
! transfer control to the appropriate re-entry point..........
! this has already been handled by the computed go to .
! end cases v
50 continue
!
! end initialization, etc.
!
! ******************************************************************
! * loop through the following 4 stages, once for each trial step *
! * until the occurrence of one of the following *
! * (a) the normal return (with ind .eq. 3) on reaching xend in *
! * stage 4 *
! * (b) an error return (with ind .lt. 0) in stage 1 or stage 4 *
! * (c) an interrupt return (with ind .eq. 4, 5 or 6), if *
! * requested, in stage 1 or stage 4 *
! ******************************************************************
!
99999 continue
!
! ***************************************************************
! * stage 1 - prepare - do calculations of hmin, hmax, etc., *
! * and some parameter checking, and end up with suitable *
! * values of hmag, xtrial and htrial in preparation for taking *
! * an integration step. *
! ***************************************************************
!
!***********error return (with ind=-1) if no of fcn evals too great
if (c(7).eq.0._dl .or. c(24).lt.c(7)) go to 100
ind = -1
return
100 continue
!
! calculate slope (adding 1 to no of fcn evals) if ind .ne. 6
if (ind .eq. 6) go to 105
call fcn(EV,n, x, y, w(1,1))
c(24) = c(24) + 1._dl
105 continue
!
! calculate hmin - use default unless value prescribed
c(13) = c(3)
if (c(3) .ne. 0._dl) go to 165
! calculate default value of hmin
! first calculate weighted norm y - c(12) - as specified
! by the error control indicator c(1)
temp = 0._dl
if (c(1) .ne. 1._dl) go to 115
! absolute error control - weights are 1
do 110 k = 1, n
temp = dmax1(temp, dabs(y(k)))
110 continue
c(12) = temp
go to 160
115 if (c(1) .ne. 2._dl) go to 120
! relative error control - weights are 1/dabs(y(k)) so
! weighted norm y is 1
c(12) = 1._dl
go to 160
120 if (c(1) .ne. 3._dl) go to 130
! weights are 1/max(c(2),abs(y(k)))
do 125 k = 1, n
temp = dmax1(temp, dabs(y(k))/c(2))
125 continue
c(12) = dmin1(temp, 1._dl)
go to 160
130 if (c(1) .ne. 4._dl) go to 140
! weights are 1/max(c(k+30),abs(y(k)))
do 135 k = 1, n
temp = dmax1(temp, dabs(y(k))/c(k+30))
135 continue
c(12) = dmin1(temp, 1._dl)
go to 160
140 if (c(1) .ne. 5._dl) go to 150
! weights are 1/c(k+30)
do 145 k = 1, n
temp = dmax1(temp, dabs(y(k))/c(k+30))
145 continue
c(12) = temp
go to 160
150 continue
! default case - weights are 1/max(1,abs(y(k)))
do 155 k = 1, n
temp = dmax1(temp, dabs(y(k)))
155 continue
c(12) = dmin1(temp, 1._dl)
160 continue
c(13) = 10._dl*dmax1(c(11),c(10)*dmax1(c(12)/tol,dabs(x)))
165 continue
!
! calculate scale - use default unless value prescribed
c(15) = c(5)
if (c(5) .eq. 0._dl) c(15) = 1._dl
!
! calculate hmax - consider 4 cases
! case 1 both hmax and scale prescribed
if (c(6).ne.0._dl .and. c(5).ne.0._dl) &
c(16) = dmin1(c(6), 2._dl/c(5))
! case 2 - hmax prescribed, but scale not
if (c(6).ne.0._dl .and. c(5).eq.0._dl) c(16) = c(6)
! case 3 - hmax not prescribed, but scale is
if (c(6).eq.0._dl .and. c(5).ne.0._dl) c(16) = 2._dl/c(5)
! case 4 - neither hmax nor scale is provided
if (c(6).eq.0._dl .and. c(5).eq.0._dl) c(16) = 2._dl
!
!***********error return (with ind=-2) if hmin .gt. hmax
if (c(13) .le. c(16)) go to 170
ind = -2
return
170 continue
!
! calculate preliminary hmag - consider 3 cases
if (ind .gt. 2) go to 175
! case 1 - initial entry - use prescribed value of hstart, if
! any, else default
c(14) = c(4)
if (c(4) .eq. 0._dl) c(14) = c(16)*tol**(1._dl/6._dl)
go to 185
175 if (c(23) .gt. 1._dl) go to 180
! case 2 - after a successful step, or at most one failure,
! use min(2, .9*(tol/est)**(1/6))*hmag, but avoid possible
! overflow. then avoid reduction by more than half.
temp = 2._dl*c(14)
if (tol .lt. (2._dl/.9d0)**6*c(19)) &
temp = .9d0*(tol/c(19))**(1._dl/6._dl)*c(14)
c(14) = dmax1(temp, .5d0*c(14))
go to 185
180 continue
! case 3 - after two or more successive failures
c(14) = .5d0*c(14)
185 continue
!
! check against hmax
c(14) = dmin1(c(14), c(16))
!
! check against hmin
c(14) = dmax1(c(14), c(13))
!
!***********interrupt no 1 (with ind=4) if requested
if (c(8) .eq. 0._dl) go to 1111
ind = 4
return
! resume here on re-entry with ind .eq. 4 ........re-entry..
1111 continue
!
! calculate hmag, xtrial - depending on preliminary hmag, xend
if (c(14) .ge. dabs(xend - x)) go to 190
! do not step more than half way to xend
c(14) = dmin1(c(14), .5d0*dabs(xend - x))
c(17) = x + dsign(c(14), xend - x)
go to 195
190 continue
! hit xend exactly
c(14) = dabs(xend - x)
c(17) = xend
195 continue
!
! calculate htrial
c(18) = c(17) - x
!
! end stage 1
!
! ***************************************************************
! * stage 2 - calculate ytrial (adding 7 to no of fcn evals). *
! * w(*,2), ... w(*,8) hold intermediate results needed in *
! * stage 3. w(*,9) is temporary storage until finally it holds *
! * ytrial. *
! ***************************************************************
!
temp = c(18)/1398169080000._dl
!
do 200 k = 1, n
w(k,9) = y(k) + temp*w(k,1)*233028180000._dl
200 continue
call fcn(EV,n, x + c(18)/6._dl, w(1,9), w(1,2))
!
do 205 k = 1, n
w(k,9) = y(k) + temp*( w(k,1)*74569017600._dl &
+ w(k,2)*298276070400._dl )
205 continue
call fcn(EV,n, x + c(18)*(4._dl/15._dl), w(1,9), w(1,3))
!
do 210 k = 1, n
w(k,9) = y(k) + temp*( w(k,1)*1165140900000._dl &
- w(k,2)*3728450880000._dl &
+ w(k,3)*3495422700000._dl )
210 continue
call fcn(EV,n, x + c(18)*(2._dl/3._dl), w(1,9), w(1,4))
!
do 215 k = 1, n
w(k,9) = y(k) + temp*( - w(k,1)*3604654659375._dl &
+ w(k,2)*12816549900000._dl &
- w(k,3)*9284716546875._dl &
+ w(k,4)*1237962206250._dl )
215 continue
call fcn(EV,n, x + c(18)*(5._dl/6._dl), w(1,9), w(1,5))
!
do 220 k = 1, n
w(k,9) = y(k) + temp*( w(k,1)*3355605792000._dl &
- w(k,2)*11185352640000._dl &
+ w(k,3)*9172628850000._dl &
- w(k,4)*427218330000._dl &
+ w(k,5)*482505408000._dl )
220 continue
call fcn(EV,n, x + c(18), w(1,9), w(1,6))
!
do 225 k = 1, n
w(k,9) = y(k) + temp*( - w(k,1)*770204740536._dl &
+ w(k,2)*2311639545600._dl &
- w(k,3)*1322092233000._dl &
- w(k,4)*453006781920._dl &
+ w(k,5)*326875481856._dl )
225 continue
call fcn(EV,n, x + c(18)/15._dl, w(1,9), w(1,7))
!
do 230 k = 1, n
w(k,9) = y(k) + temp*( w(k,1)*2845924389000._dl &
- w(k,2)*9754668000000._dl &
+ w(k,3)*7897110375000._dl &
- w(k,4)*192082660000._dl &
+ w(k,5)*400298976000._dl &
+ w(k,7)*201586000000._dl )
230 continue
call fcn(EV,n, x + c(18), w(1,9), w(1,8))
!
! calculate ytrial, the extrapolated approximation and store
! in w(*,9)
do 235 k = 1, n
w(k,9) = y(k) + temp*( w(k,1)*104862681000._dl &
+ w(k,3)*545186250000._dl &
+ w(k,4)*446637345000._dl &
+ w(k,5)*188806464000._dl &
+ w(k,7)*15076875000._dl &
+ w(k,8)*97599465000._dl )
235 continue
!
! add 7 to the no of fcn evals
c(24) = c(24) + 7._dl
!
! end stage 2
!
! ***************************************************************