From 4c24a76f4867e9e78e572db3cf503f20100ff6ab Mon Sep 17 00:00:00 2001
From: cott <cott@8e189c6b-2ab8-4400-aa02-70a9cfce18b9>
Date: Sun, 5 Dec 2010 01:29:37 +0000
Subject: * add missing file

git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinEOS/EOS_Omni/trunk@29 8e189c6b-2ab8-4400-aa02-70a9cfce18b9
---
 src/nuc_eos/findrho.F90 | 112 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 src/nuc_eos/findrho.F90

diff --git a/src/nuc_eos/findrho.F90 b/src/nuc_eos/findrho.F90
new file mode 100644
index 0000000..bf575dc
--- /dev/null
+++ b/src/nuc_eos/findrho.F90
@@ -0,0 +1,112 @@
+!-*-f90-*-
+subroutine findrho_press(lr0,lt,y,lpressin,keyerrr,tol)
+
+  use eosmodule
+
+  implicit none
+
+  !given initial guess of density
+  real*8 :: lr0
+  !working density
+  real*8 :: lr, lr_lastguess
+  !given T and Ye
+  real*8 :: lt,y
+  !pressure corresponding to lr1,lt,y
+  real*8 :: lpressin
+  
+  !accuracy we need rho to, ~1 part in tol^{-1}
+  real*8 :: tol
+  !will be derivatives of pressure wrt rho,T,ye
+  real*8 :: d1,d2,d3
+  !helpers along the way
+  real*8 :: lpress_of_guess,lpress_of_lastguess,first_lpress,ldr,lr_new
+  !bounds of density
+  real*8 :: lrmax,lrmin
+  !counters & flags
+  integer :: rl = 0
+  integer :: itmax,i,keyerrr
+  
+  keyerrr=0
+
+  itmax=20 ! use at most 20 iterations, then bisection
+
+  lr=lr0
+
+  lrmax=logrho(nrho)
+  lrmin=logrho(1)
+
+  !Note: We are using Ewald's Lagrangian interpolator here!
+
+  !first use initial guess to estimate derivatives
+  call findthis(lr,lt,y,lpress_of_guess,alltables(:,:,:,1),d1,d2,d3)
+  
+  first_lpress = lpress_of_guess
+
+  !preconditioning 1: do we already have the right rho?
+  if (abs(lpressin-lpress_of_guess).lt.tol*abs(lpressin)) then
+     lr0 = lr
+     return
+  endif
+
+
+  !otherwise we must newton-raphson to get the real rho
+  do i=1,itmax
+
+     !d1 is the derivative dlpress/dlogrho, use to guess hopefully better rho
+!     write(*,*) i,lr,d1,lpressin-lpress_of_guess
+     ldr= (lpressin-lpress_of_guess)/d1 
+     if (abs(ldr).gt.5.0d0) then
+        write(*,*) i,ldr,d1,lr,lr_new
+        keyerrr = 473
+        write(*,*) "dpdrho very small"
+        return
+     endif
+     lr_new = lr+ldr
+
+     !make sure we do not go out of bounds
+     lr_new = min(lr_new,lrmax)
+     lr_new = max(lr_new,lrmin)
+
+     !keep old variables incase we want to make our own derivatives
+     lpress_of_lastguess = lpress_of_guess
+     lr_lastguess = lr
+     
+     !use to get next iteration of NR
+     lr = lr_new     
+     call findthis(lr,lt,y,lpress_of_guess,alltables(:,:,:,1),d1,d2,d3)
+     if (abs(lpressin - lpress_of_guess).lt.tol*abs(lpressin)) then
+        !yes, we got it!
+        lr0 = lr
+        return
+     endif
+
+     ! if we are closer than 10^-3  to the 
+     ! root (lpressin-lpress_of_guess)=0, we are switching to 
+     ! the secant method, since the table is rather coarse and the
+     ! derivatives may be garbage.
+     if(abs(lpressin-lpress_of_guess).lt.1.0d-3*abs(lpressin)) then
+        d1 = (lpress_of_guess-lpress_of_lastguess)/(lr-lr_lastguess)
+     endif
+
+  enddo
+
+  !we may fail in the NR, after itmax reached.  Then we revert to the bisection method.
+  if(i.ge.itmax) then
+     keyerrr=667
+     call bisection_rho(lr0,lt,y,lpressin,lr,alltables(:,:,:,1),keyerrr,3)
+     if(keyerrr.eq.667) then
+        ! total failure
+        call findthis(lr,lt,y,lpress_of_guess,alltables(:,:,:,1),d1,d2,d3)
+        write(*,*) "EOS: Did not converge in findrho_press!"
+        write(*,*) "iteration,logrho0,logtemp,ye,lpressin,lpress_first,rhoreturn,press_of_rhoreturn"
+        write(*,"(i4,1P10E19.10)") i,lr0,lt,y,lpressin,first_lpress,lr,lpress_of_guess
+        write(*,*) "Tried calling bisection... didn't help... :-/"
+        write(*,*) "Bisection error: ",keyerrr
+     endif
+  endif
+    
+  lr0 = lr
+  return
+
+
+end subroutine findrho_press
-- 
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