From 5978792a58004e4a60b9372bc75e4d7d7dce35fb Mon Sep 17 00:00:00 2001
From: Anthony Scemama <scemama@irsamc.ups-tlse.fr>
Date: Tue, 4 Jun 2019 10:44:03 +0200
Subject: [PATCH] Add rpt2 matching

---
 devel/variance/rpt2_match.irp.f | 118 ++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 devel/variance/rpt2_match.irp.f

diff --git a/devel/variance/rpt2_match.irp.f b/devel/variance/rpt2_match.irp.f
new file mode 100644
index 0000000..cb18fe1
--- /dev/null
+++ b/devel/variance/rpt2_match.irp.f
@@ -0,0 +1,118 @@
+program variance
+  implicit none
+  BEGIN_DOC
+! Selected Full Configuration Interaction with Stochastic selection and PT2.
+  END_DOC
+  integer                        :: i,j,k
+  double precision, allocatable  :: pt2(:), var(:), norm(:), rpt2(:)
+  integer                        :: to_select
+  logical, external :: qp_stop
+
+  double precision :: rss
+  double precision, external :: memory_of_double
+  PROVIDE H_apply_buffer_allocated N_generators_bitmask
+
+  threshold_generators = 1.d0
+  SOFT_TOUCH threshold_generators
+
+  rss = memory_of_double(N_states)*4.d0
+  call check_mem(rss,irp_here)
+
+  allocate (pt2(N_states), rpt2(N_states), norm(N_states), var(N_states))
+
+  double precision               :: hf_energy_ref
+  logical                        :: has
+  double precision               :: relative_error
+
+  relative_error=PT2_relative_error
+
+  pt2 = -huge(1.e0)
+  rpt2 = -huge(1.e0)
+  norm = 0.d0
+  var = huge(1.e0)
+
+  if (s2_eig) then
+    call make_s2_eigenfunction
+  endif
+  call diagonalize_CI
+  call save_wavefunction
+
+  call ezfio_has_hartree_fock_energy(has)
+  if (has) then
+    call ezfio_get_hartree_fock_energy(hf_energy_ref)
+  else
+    hf_energy_ref = ref_bitmask_energy
+  endif
+
+  if (N_det > N_det_max) then
+    psi_det = psi_det_sorted
+    psi_coef = psi_coef_sorted
+    N_det = N_det_max
+    soft_touch N_det psi_det psi_coef
+    if (s2_eig) then
+      call make_s2_eigenfunction
+    endif
+    call diagonalize_CI
+    call save_wavefunction
+  endif
+
+  double precision :: correlation_energy_ratio
+  double precision :: error(N_states)
+
+  correlation_energy_ratio = 0.d0
+
+  do while (                                                         &
+        (N_det < N_det_max) .and.                                    &
+        (maxval(abs(rpt2(1:N_states))) > pt2_max) .and.               &
+        (maxval(abs(var(1:N_states))) > variance_max) .and.     &
+        (correlation_energy_ratio <= correlation_energy_ratio_max)   &
+        )
+      write(*,'(A)')  '--------------------------------------------------------------------------------'
+
+
+    to_select = N_det/20
+    to_select = max(N_states_diag, to_select)
+
+    pt2 = 0.d0
+    var = 0.d0
+    norm = 0.d0
+    call ZMQ_pt2(psi_energy_with_nucl_rep,pt2,relative_error,error, var, &
+      norm, to_select) ! Stochastic PT2 and selection
+
+    correlation_energy_ratio = (psi_energy_with_nucl_rep(1) - hf_energy_ref)  /     &
+                    (psi_energy_with_nucl_rep(1) + pt2(1) - hf_energy_ref)
+    correlation_energy_ratio = min(1.d0,correlation_energy_ratio)
+
+    call save_energy(psi_energy_with_nucl_rep, pt2)
+    call write_double(6,correlation_energy_ratio, 'Correlation ratio')
+    call print_summary(psi_energy_with_nucl_rep,pt2,error,var,norm,N_det,N_occ_pattern,N_states,psi_s2)
+
+    do k=1,N_states
+      rpt2(:) = pt2(:)/(1.d0 + norm(k))
+    enddo
+
+    call save_iterations(psi_energy_with_nucl_rep(1:N_states),rpt2,N_det)
+    call print_extrapolated_energy()
+    N_iter += 1
+    
+    if ( (maxval(abs(rpt2(1:N_states))) <= pt2_max) .or.              &
+          (maxval(abs(var(1:N_states))) <= variance_max) .or.        &
+          qp_stop() ) then
+         exit
+    endif
+    ! Add selected determinants
+    call copy_H_apply_buffer_to_wf()
+    call save_wavefunction
+
+    PROVIDE  psi_coef
+    PROVIDE  psi_det
+    PROVIDE  psi_det_sorted
+
+    call diagonalize_CI
+    call save_wavefunction
+    rpt2(:) = 0.d0
+    call save_energy(psi_energy_with_nucl_rep, rpt2)
+    if (qp_stop()) exit 
+  enddo
+
+end