Chem preprocess speedup (#851)

Author: DimAdam-01

src/common/m_chemistry.fpp

@@ -9,7 +9,8 @@
 module m_chemistry
 
     use m_thermochem, only: &
-        num_species, molecular_weights, get_temperature, get_net_production_rates
+        num_species, molecular_weights, get_temperature, get_net_production_rates, &
+        gas_constant, get_mixture_molecular_weight
 
     use m_global_parameters
 
@@ -58,6 +59,32 @@ contains
 
     end subroutine s_compute_q_T_sf
 
+    subroutine s_compute_T_from_primitives(q_T_sf, q_prim_vf, bounds)
+
+        type(scalar_field), intent(inout) :: q_T_sf
+        type(scalar_field), dimension(sys_size), intent(in) :: q_prim_vf
+        type(int_bounds_info), dimension(1:3), intent(in) :: bounds
+
+        integer :: x, y, z, i
+        real(wp), dimension(num_species) :: Ys
+        real(wp) :: mix_mol_weight
+
+        do z = bounds(3)%beg, bounds(3)%end
+            do y = bounds(2)%beg, bounds(2)%end
+                do x = bounds(1)%beg, bounds(1)%end
+                    !$acc loop seq
+                    do i = chemxb, chemxe
+                        Ys(i - chemxb + 1) = q_prim_vf(i)%sf(x, y, z)
+                    end do
+
+                    call get_mixture_molecular_weight(Ys, mix_mol_weight)
+                    q_T_sf%sf(x, y, z) = q_prim_vf(E_idx)%sf(x, y, z)*mix_mol_weight/(gas_constant*q_prim_vf(1)%sf(x, y, z))
+                end do
+            end do
+        end do
+
+    end subroutine s_compute_T_from_primitives
+
     subroutine s_compute_chemistry_reaction_flux(rhs_vf, q_cons_qp, q_T_sf, q_prim_qp, bounds)
 
         type(scalar_field), dimension(sys_size), intent(inout) :: rhs_vf

src/pre_process/m_initial_condition.fpp

@@ -175,9 +175,6 @@ contains
         !!              primitive variables are converted to conservative ones.
     subroutine s_generate_initial_condition
 
-        ! First, compute the temperature field from the conservative variables.
-        if (chemistry) call s_compute_q_T_sf(q_T_sf, q_cons_vf, idwint)
-
         ! Converting the conservative variables to the primitive ones given
         ! preexisting initial condition data files were read in on start-up
         if (old_ic) then
@@ -198,7 +195,7 @@ contains
         ! Converting the primitive variables to the conservative ones
         call s_convert_primitive_to_conservative_variables(q_prim_vf, q_cons_vf)
 
-        if (chemistry) call s_compute_q_T_sf(q_T_sf, q_cons_vf, idwint)
+        if (chemistry) call s_compute_T_from_primitives(q_T_sf, q_prim_vf, idwint)
 
         if (qbmm .and. .not. polytropic) then
             !Initialize pb and mv