diff --git a/plugins/MRCC_Utils/mrcc_utils.irp.f b/plugins/MRCC_Utils/mrcc_utils.irp.f
index 8873a940..42058145 100644
--- a/plugins/MRCC_Utils/mrcc_utils.irp.f
+++ b/plugins/MRCC_Utils/mrcc_utils.irp.f
@@ -288,7 +288,8 @@ logical function is_generable(det1, det2, Nint)
   implicit none
   integer, intent(in) :: Nint
   integer(bit_kind) :: det1(Nint, 2), det2(Nint, 2)
-  integer :: degree, f, exc(0:2, 2, 2), h1, h2, p1, p2, s1, s2, t
+  integer :: degree, f, exc(0:2, 2, 2), t
+  integer*2 :: h1, h2, p1, p2, s1, s2
   integer, external :: searchExc
   logical, external :: excEq
   double precision :: phase
@@ -312,7 +313,7 @@ logical function is_generable(det1, det2, Nint)
 ! !   print *, f
 !   return
   
-  call decode_exc(exc,degree,h1,p1,h2,p2,s1,s2)
+  call decode_exc_int2(exc,degree,h1,p1,h2,p2,s1,s2)
   
   if(degree == 1) then
     h2 = h1
@@ -323,14 +324,14 @@ logical function is_generable(det1, det2, Nint)
     s1 = 0
   end if
   
-  if(h1 + s1*mo_tot_num < h2 + s2*mo_tot_num) then
+  if(h1 + (s1-1)*mo_tot_num < h2 + (s2-1)*mo_tot_num) then
     f = searchExc(hh_exists(1,1), (/s1, h1, s2, h2/),  hh_shortcut(0))
   else
     f = searchExc(hh_exists(1,1), (/s2, h2, s1, h1/), hh_shortcut(0))
   end if
   if(f == -1) return
   
-  if(p1 + s1*mo_tot_num < p2 + s2*mo_tot_num) then
+  if(p1 + (s1-1)*mo_tot_num < p2 + (s2-1)*mo_tot_num) then
     f = searchExc(pp_exists(1,hh_shortcut(f)), (/s1, p1, s2, p2/), hh_shortcut(f+1)-hh_shortcut(f))
   else
     f = searchExc(pp_exists(1,hh_shortcut(f)), (/s2, p2, s1, p1/), hh_shortcut(f+1)-hh_shortcut(f))
@@ -376,7 +377,7 @@ integer function searchExc(excs, exc, n)
   use bitmasks
   
   integer, intent(in) :: n
-  integer,intent(in) :: excs(4,n), exc(4)
+  integer*2,intent(in) :: excs(4,n), exc(4)
   integer :: l, h, c
   integer, external :: excCmp
   logical, external :: excEq
@@ -441,8 +442,8 @@ subroutine sort_exc(key, N_key)
   
 
   integer, intent(in)                   :: N_key
-  integer,intent(inout)       :: key(4,N_key)
-  integer                     :: tmp(4)
+  integer*2,intent(inout)       :: key(4,N_key)
+  integer*2                     :: tmp(4)
   integer                               :: i,ni
   
   
@@ -464,7 +465,7 @@ end subroutine
 
 logical function exc_inf(exc1, exc2)
   implicit none
-  integer,intent(in) :: exc1(4), exc2(4)
+  integer*2,intent(in) :: exc1(4), exc2(4)
   integer :: i
   exc_inf = .false.
   do i=1,4
@@ -486,9 +487,9 @@ subroutine tamise_exc(key, no, n, N_key)
 ! Uncodumented : TODO
   END_DOC
   integer,intent(in)                    :: no, n, N_key
-  integer,intent(inout)       :: key(4, N_key)
+  integer*2,intent(inout)       :: key(4, N_key)
   integer                               :: k,j
-  integer                    :: tmp(4)
+  integer*2                    :: tmp(4)
   logical                               :: exc_inf
   integer                               :: ni
   
@@ -518,7 +519,7 @@ end subroutine
 subroutine dec_exc(exc, h1, h2, p1, p2)
   implicit none
   integer :: exc(0:2,2,2), s1, s2, degree
-  integer, intent(out) :: h1, h2, p1, p2
+  integer*2, intent(out) :: h1, h2, p1, p2
   
   degree = exc(0,1,1) + exc(0,1,2)
   
@@ -529,7 +530,7 @@ subroutine dec_exc(exc, h1, h2, p1, p2)
     
   if(degree == 0) return
   
-  call decode_exc(exc, degree, h1, p1, h2, p2, s1, s2)
+  call decode_exc_int2(exc, degree, h1, p1, h2, p2, s1, s2)
   
   h1 += mo_tot_num * (s1-1)
   p1 += mo_tot_num * (s1-1)
@@ -556,12 +557,13 @@ subroutine dec_exc(exc, h1, h2, p1, p2)
 end subroutine
 
 
- BEGIN_PROVIDER [ integer, hh_exists, (4, N_det_ref * N_det_non_ref) ]
+ BEGIN_PROVIDER [ integer*2, hh_exists, (4, N_det_ref * N_det_non_ref) ]
 &BEGIN_PROVIDER [ integer, hh_shortcut, (0:N_det_ref * N_det_non_ref + 1) ]
-&BEGIN_PROVIDER [ integer, pp_exists, (4, N_det_ref * N_det_non_ref) ]
+&BEGIN_PROVIDER [ integer*2, pp_exists, (4, N_det_ref * N_det_non_ref) ]
   implicit none
-  integer,allocatable :: num(:,:)
-  integer :: exc(0:2, 2, 2), degree, n, on, s, h1, h2, p1, p2, l, i
+  integer*2,allocatable :: num(:,:)
+  integer :: exc(0:2, 2, 2), degree, n, on, s, l, i
+  integer*2 :: h1, h2, p1, p2
   double precision :: phase
   logical, external :: excEq
   
@@ -587,19 +589,19 @@ end subroutine
   
   hh_shortcut(0) = 1
   hh_shortcut(1) = 1
-  hh_exists(:,1) = (/1, num(1,1), 1, num(2,1)/)
-  pp_exists(:,1) = (/1, num(3,1), 1, num(4,1)/)
+  hh_exists(:,1) = (/1_2, num(1,1), 1_2, num(2,1)/)
+  pp_exists(:,1) = (/1_2, num(3,1), 1_2, num(4,1)/)
   s = 1
   do i=2,n
     if(.not. excEq(num(1,i), num(1,s))) then
       s += 1
       num(:, s) = num(:, i)
-      pp_exists(:,s) = (/1, num(3,s), 1, num(4,s)/)
+      pp_exists(:,s) = (/1_2, num(3,s), 1_2, num(4,s)/)
       if(hh_exists(2, hh_shortcut(0)) /= num(1,s) .or. &
             hh_exists(4, hh_shortcut(0)) /= num(2,s)) then
         hh_shortcut(0) += 1
         hh_shortcut(hh_shortcut(0)) = s
-        hh_exists(:,hh_shortcut(0)) = (/1, num(1,s), 1, num(2,s)/)
+        hh_exists(:,hh_shortcut(0)) = (/1_2, num(1,s), 1_2, num(2,s)/)
       end if
     end if
   end do
@@ -629,7 +631,7 @@ END_PROVIDER
 
 logical function excEq(exc1, exc2)
   implicit none
-  integer, intent(in) :: exc1(4), exc2(4)
+  integer*2, intent(in) :: exc1(4), exc2(4)
   integer :: i
   excEq = .false.
   do i=1, 4
@@ -641,7 +643,7 @@ end function
 
 integer function excCmp(exc1, exc2)
   implicit none
-  integer, intent(in) :: exc1(4), exc2(4)
+  integer*2, intent(in) :: exc1(4), exc2(4)
   integer :: i
   excCmp = 0
   do i=1, 4
@@ -660,8 +662,8 @@ subroutine apply_hole(det, exc, res, ok, Nint)
   use bitmasks
   implicit none
   integer, intent(in) :: Nint
-  integer, intent(in) :: exc(4)
-  integer :: s1, s2, h1, h2
+  integer*2, intent(in) :: exc(4)
+  integer*2 :: s1, s2, h1, h2
   integer(bit_kind),intent(in) :: det(Nint, 2)
   integer(bit_kind),intent(out) :: res(Nint, 2)
   logical, intent(out) :: ok
@@ -695,8 +697,8 @@ subroutine apply_particle(det, exc, res, ok, Nint)
   use bitmasks
   implicit none
   integer, intent(in) :: Nint
-  integer, intent(in) :: exc(4)
-  integer :: s1, s2, p1, p2
+  integer*2, intent(in) :: exc(4)
+  integer*2 :: s1, s2, p1, p2
   integer(bit_kind),intent(in) :: det(Nint, 2)
   integer(bit_kind),intent(out) :: res(Nint, 2)
   logical, intent(out) :: ok
diff --git a/plugins/mrcepa0/dressing.irp.f b/plugins/mrcepa0/dressing.irp.f
index 5d8d4850..4f99f6e1 100644
--- a/plugins/mrcepa0/dressing.irp.f
+++ b/plugins/mrcepa0/dressing.irp.f
@@ -6,16 +6,28 @@ use bitmasks
 &BEGIN_PROVIDER [ double precision, delta_ii_mrcc, (N_states, N_det_ref) ]
   use bitmasks
   implicit none
-  integer :: gen, h, p, i_state, n, t, i, h1, h2, p1, p2, s1, s2
-  integer(bit_kind) :: mask(N_int, 2), omask(N_int, 2), buf(N_int, 2, N_det_non_ref)
+  integer :: gen, h, p, i_state, n, t, i, h1, h2, p1, p2, s1, s2, iproc
+  integer(bit_kind) :: mask(N_int, 2), omask(N_int, 2)
+  integer(bit_kind), allocatable :: buf(:,:,:)
+  double precision, allocatable :: delta_ij_mwen(:,:,:,:), delta_ii_mwen(:,:,:)
   logical :: ok
   logical, external :: detEq
   
   delta_ij_mrcc = 0d0
   delta_ii_mrcc = 0d0
   i_state = 1
+  provide hh_shortcut psi_det_size
+  allocate(delta_ij_mwen(N_states,N_det_non_ref,N_det_ref,nproc), delta_ii_mwen(N_states,N_det_ref,nproc))
+  allocate(buf(N_int, 2, N_det_non_ref))
+  delta_ij_mwen = 0d0
+  delta_ii_mwen = 0d0
   
+  !$OMP PARALLEL DO default(none)  schedule(dynamic) &
+  !$OMP shared(psi_det_generators, N_det_generators, hh_exists, pp_exists, N_int, hh_shortcut) &
+  !$OMP shared(N_states, N_det_non_ref, N_det_ref, delta_ii_mwen, delta_ij_mwen) &
+  !$OMP private(h, n, mask, omask, buf, ok, iproc)
   do gen= 1, N_det_generators
+    iproc = omp_get_thread_num() + 1
     print *, gen, "/", N_det_generators
     do h=1, hh_shortcut(0)
       call apply_hole(psi_det_generators(1,1,gen), hh_exists(1, h), mask, ok, N_int)
@@ -28,12 +40,23 @@ use bitmasks
         if(ok) n = n + 1
       end do
       n = n - 1
-      if(n /= 0) call mrcc_part_dress(delta_ij_mrcc, delta_ii_mrcc,gen,n,buf,N_int,omask)
+      if(n /= 0) call mrcc_part_dress(delta_ij_mwen(1,1,1,iproc), delta_ii_mwen(1,1,iproc),gen,n,buf,N_int,omask)
     end do
   end do
+  !$OMP END PARALLEL DO
+  do iproc=1, nproc
+    delta_ij_mrcc = delta_ij_mrcc + delta_ij_mwen(:,:,:,iproc)
+    delta_ii_mrcc = delta_ii_mrcc + delta_ii_mwen(:,:,iproc)
+  end do
 END_PROVIDER
 
 
+! subroutine blit(b1, b2)
+!   double precision :: b1(N_states,N_det_non_ref,N_det_ref), b2(N_states,N_det_non_ref,N_det_ref)
+!   b1 = b1 + b2
+! end subroutine
+
+
 subroutine mrcc_part_dress(delta_ij_, delta_ii_,i_generator,n_selected,det_buffer,Nint,key_mask)
  use bitmasks
  implicit none
@@ -463,7 +486,7 @@ END_PROVIDER
   double precision :: Hjk, Hki, Hij, pre(N_det_ref), wall
   integer :: i_state, degree, npre, ipre(N_det_ref), npres(N_det_ref)
   
-  provide lambda_mrcc
+!   provide lambda_mrcc
   npres = 0
   delta_cas = 0d0
   call wall_time(wall)
@@ -605,8 +628,8 @@ end function
 
   call wall_time(wall)
   print *, "cepa0", wall
-  provide det_cepa0_active delta_cas lambda_mrcc
-  provide mo_bielec_integrals_in_map
+!   provide det_cepa0_active delta_cas lambda_mrcc
+!   provide mo_bielec_integrals_in_map
   allocate(idx_sorted_bit(N_det))
   
   sortRef(:,:,:) = det_ref_active(:,:,:)
diff --git a/src/Determinants/slater_rules.irp.f b/src/Determinants/slater_rules.irp.f
index 2b5ae4f1..3374dfb2 100644
--- a/src/Determinants/slater_rules.irp.f
+++ b/src/Determinants/slater_rules.irp.f
@@ -139,6 +139,72 @@ subroutine decode_exc(exc,degree,h1,p1,h2,p2,s1,s2)
 end
 
 
+subroutine decode_exc_int2(exc,degree,h1,p1,h2,p2,s1,s2)
+  use bitmasks
+  implicit none
+  BEGIN_DOC
+  ! Decodes the exc arrays returned by get_excitation.
+  ! h1,h2 : Holes
+  ! p1,p2 : Particles
+  ! s1,s2 : Spins (1:alpha, 2:beta)
+  ! degree : Degree of excitation
+  END_DOC
+  integer, intent(in)            :: exc(0:2,2,2),degree
+  integer*2, intent(out)           :: h1,h2,p1,p2,s1,s2
+  ASSERT (degree > 0)
+  ASSERT (degree < 3)
+  
+  select case(degree)
+    case(2)
+      if (exc(0,1,1) == 2) then
+        h1 = exc(1,1,1)
+        h2 = exc(2,1,1)
+        p1 = exc(1,2,1)
+        p2 = exc(2,2,1)
+        s1 = 1
+        s2 = 1
+      else if (exc(0,1,2) == 2) then
+        h1 = exc(1,1,2)
+        h2 = exc(2,1,2)
+        p1 = exc(1,2,2)
+        p2 = exc(2,2,2)
+        s1 = 2
+        s2 = 2
+      else
+        h1 = exc(1,1,1)
+        h2 = exc(1,1,2)
+        p1 = exc(1,2,1)
+        p2 = exc(1,2,2)
+        s1 = 1
+        s2 = 2
+      endif
+    case(1)
+      if (exc(0,1,1) == 1) then
+        h1 = exc(1,1,1)
+        h2 = 0
+        p1 = exc(1,2,1)
+        p2 = 0
+        s1 = 1
+        s2 = 0
+      else
+        h1 = exc(1,1,2)
+        h2 = 0
+        p1 = exc(1,2,2)
+        p2 = 0
+        s1 = 2
+        s2 = 0
+      endif
+    case(0)
+      h1 = 0
+      p1 = 0
+      h2 = 0
+      p2 = 0
+      s1 = 0
+      s2 = 0
+  end select
+end
+
+
 subroutine get_double_excitation(det1,det2,exc,phase,Nint)
   use bitmasks
   implicit none