diff --git a/RELEASE_NOTES.org b/RELEASE_NOTES.org
index 6e46d868..a913149e 100644
--- a/RELEASE_NOTES.org
+++ b/RELEASE_NOTES.org
@@ -53,6 +53,7 @@
     - Added ~print_energy~
     - Added ~print_hamiltonian~
     - Added input for two body RDM
+    - Added keyword ~save_wf_after_selection~ 
 
 *** Code
 
@@ -79,3 +80,4 @@
       
 
 
+    
diff --git a/docs/source/users_guide/quickstart.rst b/docs/source/users_guide/quickstart.rst
index f0620c5a..e55adcb7 100644
--- a/docs/source/users_guide/quickstart.rst
+++ b/docs/source/users_guide/quickstart.rst
@@ -128,6 +128,12 @@ and the atomic basis set:
   ao_two_e_erf_ints  density_for_dft       electrons     mo_two_e_ints      scf_utils
   ao_two_e_ints      determinants          ezfio         nuclei             work
 
+If you need to run using an already existing EZFIO database, use
+
+.. code::  bash
+
+  qp set_file hcn
+
 
 Run a Hartree-Fock calculation
 ------------------------------
diff --git a/src/cipsi/EZFIO.cfg b/src/cipsi/EZFIO.cfg
index 7d3a5fde..3fdf74d2 100644
--- a/src/cipsi/EZFIO.cfg
+++ b/src/cipsi/EZFIO.cfg
@@ -4,6 +4,12 @@ doc: If true, computes the one- and two-body rdms with perturbation theory
 interface: ezfio,provider,ocaml
 default: False
 
+[save_wf_after_selection]
+type: logical
+doc: If true, saves the wave function after the selection, before the diagonalization
+interface: ezfio,provider,ocaml
+default: False
+
 [seniority_max]
 type: integer
 doc: Maximum number of allowed open shells. Using -1 selects all determinants
diff --git a/src/cipsi/cipsi.irp.f b/src/cipsi/cipsi.irp.f
index 112ebb56..6e715531 100644
--- a/src/cipsi/cipsi.irp.f
+++ b/src/cipsi/cipsi.irp.f
@@ -114,7 +114,10 @@ subroutine run_cipsi
 
     ! Add selected determinants
     call copy_H_apply_buffer_to_wf()
-!    call save_wavefunction
+
+    if (save_wf_after_selection) then
+      call save_wavefunction
+    endif
 
     PROVIDE  psi_coef
     PROVIDE  psi_det
diff --git a/src/cipsi/selection.irp.f b/src/cipsi/selection.irp.f
index 8ad08734..ea2345b3 100644
--- a/src/cipsi/selection.irp.f
+++ b/src/cipsi/selection.irp.f
@@ -166,6 +166,7 @@ subroutine select_singles_and_doubles(i_generator,hole_mask,particle_mask,fock_d
 
   integer                        :: l_a, nmax, idx
   integer, allocatable           :: indices(:), exc_degree(:), iorder(:)
+  double precision, parameter :: norm_thr = 1.d-16
   allocate (indices(N_det),                                          &
       exc_degree(max(N_det_alpha_unique,N_det_beta_unique)))
 
@@ -185,7 +186,7 @@ subroutine select_singles_and_doubles(i_generator,hole_mask,particle_mask,fock_d
       i = psi_bilinear_matrix_rows(l_a)
       if (nt + exc_degree(i) <= 4) then
         idx = psi_det_sorted_order(psi_bilinear_matrix_order(l_a))
-        if (psi_average_norm_contrib_sorted(idx) > 1.d-20) then
+        if (psi_average_norm_contrib_sorted(idx) > norm_thr) then
           indices(k) = idx
           k=k+1
         endif
@@ -212,7 +213,7 @@ subroutine select_singles_and_doubles(i_generator,hole_mask,particle_mask,fock_d
         idx = psi_det_sorted_order(                                  &
             psi_bilinear_matrix_order(                               &
             psi_bilinear_matrix_transp_order(l_a)))
-        if (psi_average_norm_contrib_sorted(idx) > 1.d-20) then
+        if (psi_average_norm_contrib_sorted(idx) > norm_thr) then
           indices(k) = idx
           k=k+1
         endif
@@ -742,12 +743,9 @@ subroutine fill_buffer_double(i_generator, sp, h1, h2, bannedOrb, banned, fock_d
 
         alpha_h_psi = mat(istate, p1, p2)
 
-        do jstate=1,N_states
-          pt2_data % overlap(jstate,istate) += coef(jstate) * coef(istate)
-        enddo
-
-        pt2_data % variance(istate) += alpha_h_psi * alpha_h_psi
-        pt2_data % pt2(istate)      += e_pert(istate)
+        pt2_data % overlap(:,istate) = pt2_data % overlap(:,istate) + coef(:) * coef(istate)
+        pt2_data % variance(istate)  = pt2_data % variance(istate) + alpha_h_psi * alpha_h_psi
+        pt2_data % pt2(istate)       = pt2_data % pt2(istate)      + e_pert(istate)
 
 !!!DEBUG
 !        delta_E = E0(istate) - Hii + E_shift
@@ -1578,7 +1576,7 @@ subroutine get_d0_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
           phase = get_phase_bi(phasemask, 1, 2, h1, p1, h2, p2, N_int)
           hij = mo_two_e_integral(p1, p2, h1, h2) * phase
         end if
-        mat(:, p1, p2) += coefs(:) * hij
+        mat(:, p1, p2) = mat(:, p1, p2) + coefs(:) * hij
       end do
     end do
   else ! AA BB
@@ -1595,7 +1593,7 @@ subroutine get_d0_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         else
           hij = (mo_two_e_integral(p1, p2, puti, putj) -  mo_two_e_integral(p2, p1, puti, putj))* get_phase_bi(phasemask, sp, sp, puti, p1 , putj, p2, N_int)
         end if
-        mat(:, puti, putj) += coefs(:) * hij
+        mat(:, puti, putj) = mat(:, puti, putj) + coefs(:) * hij
       end do
     end do
   end if
@@ -1654,18 +1652,18 @@ subroutine get_d1_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
       do putj=1, hfix-1
         if(lbanned(putj, ma) .or. banned(putj, puti,bant)) cycle
         hij = (mo_two_e_integral(p1, p2, putj, hfix)-mo_two_e_integral(p2,p1,putj,hfix)) * get_phase_bi(phasemask, ma, ma, putj, p1, hfix, p2, N_int)
-        tmp_row(1:N_states,putj) += hij * coefs(1:N_states)
+        tmp_row(1:N_states,putj) = tmp_row(1:N_states,putj) + hij * coefs(1:N_states)
       end do
       do putj=hfix+1, mo_num
         if(lbanned(putj, ma) .or. banned(putj, puti,bant)) cycle
         hij = (mo_two_e_integral(p1, p2, hfix, putj)-mo_two_e_integral(p2,p1,hfix,putj)) * get_phase_bi(phasemask, ma, ma, hfix, p1, putj, p2, N_int)
-        tmp_row(1:N_states,putj) += hij * coefs(1:N_states)
+        tmp_row(1:N_states,putj) = tmp_row(1:N_states,putj) + hij * coefs(1:N_states)
       end do
 
       if(ma == 1) then
-        mat(1:N_states,1:mo_num,puti) += tmp_row(1:N_states,1:mo_num)
+        mat(1:N_states,1:mo_num,puti) = mat(1:N_states,1:mo_num,puti) + tmp_row(1:N_states,1:mo_num)
       else
-        mat(1:N_states,puti,1:mo_num) += tmp_row(1:N_states,1:mo_num)
+        mat(1:N_states,puti,1:mo_num) = mat(1:N_states,puti,1:mo_num) + tmp_row(1:N_states,1:mo_num)
       end if
     end if
 
@@ -1679,22 +1677,22 @@ subroutine get_d1_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
       putj = p1
       if(.not. banned(putj,puti,bant)) then
         hij = mo_two_e_integral(p2,pfix,hfix,puti) * get_phase_bi(phasemask, ma, mi, hfix, p2, puti, pfix, N_int)
-        tmp_row(:,puti) += hij * coefs(:)
+        tmp_row(:,puti) = tmp_row(:,puti) + hij * coefs(:)
       end if
 
       putj = p2
       if(.not. banned(putj,puti,bant)) then
         hij = mo_two_e_integral(p1,pfix,hfix,puti) * get_phase_bi(phasemask, ma, mi, hfix, p1, puti, pfix, N_int)
-        tmp_row2(:,puti) += hij * coefs(:)
+        tmp_row2(:,puti) = tmp_row2(:,puti) + hij * coefs(:)
       end if
     end do
 
     if(mi == 1) then
-      mat(:,:,p1) += tmp_row(:,:)
-      mat(:,:,p2) += tmp_row2(:,:)
+      mat(:,:,p1) = mat(:,:,p1) + tmp_row(:,:)
+      mat(:,:,p2) = mat(:,:,p2) + tmp_row2(:,:)
     else
-      mat(:,p1,:) += tmp_row(:,:)
-      mat(:,p2,:) += tmp_row2(:,:)
+      mat(:,p1,:) = mat(:,p1,:) + tmp_row(:,:)
+      mat(:,p2,:) = mat(:,p2,:) + tmp_row2(:,:)
     end if
   else
     if(p(0,ma) == 3) then
@@ -1707,16 +1705,16 @@ subroutine get_d1_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         do putj=1,hfix-1
           if(lbanned(putj,ma) .or. banned(puti,putj,1)) cycle
           hij = (mo_two_e_integral(p1, p2, putj, hfix)-mo_two_e_integral(p2,p1,putj,hfix)) * get_phase_bi(phasemask, ma, ma, putj, p1, hfix, p2, N_int)
-          tmp_row(:,putj) += hij * coefs(:)
+          tmp_row(:,putj) = tmp_row(:,putj) + hij * coefs(:)
         end do
         do putj=hfix+1,mo_num
           if(lbanned(putj,ma) .or. banned(puti,putj,1)) cycle
           hij = (mo_two_e_integral(p1, p2, hfix, putj)-mo_two_e_integral(p2,p1,hfix,putj)) * get_phase_bi(phasemask, ma, ma, hfix, p1, putj, p2, N_int)
-          tmp_row(:,putj) += hij * coefs(:)
+          tmp_row(:,putj) = tmp_row(:,putj) + hij * coefs(:)
         end do
 
-        mat(:, :puti-1, puti) += tmp_row(:,:puti-1)
-        mat(:, puti, puti:) += tmp_row(:,puti:)
+        mat(:, :puti-1, puti) = mat(:, :puti-1, puti) + tmp_row(:,:puti-1)
+        mat(:, puti, puti:) = mat(:, puti, puti:) + tmp_row(:,puti:)
       end do
     else
       hfix = h(1,mi)
@@ -1730,19 +1728,19 @@ subroutine get_d1_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         putj = p2
         if(.not. banned(puti,putj,1)) then
           hij = mo_two_e_integral(pfix, p1, hfix, puti) * get_phase_bi(phasemask, mi, ma, hfix, pfix, puti, p1, N_int)
-          tmp_row(:,puti) += hij * coefs(:)
+          tmp_row(:,puti) = tmp_row(:,puti) + hij * coefs(:)
         end if
 
         putj = p1
         if(.not. banned(puti,putj,1)) then
           hij = mo_two_e_integral(pfix, p2, hfix, puti) * get_phase_bi(phasemask, mi, ma, hfix, pfix, puti, p2, N_int)
-          tmp_row2(:,puti) += hij * coefs(:)
+          tmp_row2(:,puti) = tmp_row2(:,puti) + hij * coefs(:)
         end if
       end do
-      mat(:,:p2-1,p2) += tmp_row(:,:p2-1)
-      mat(:,p2,p2:) += tmp_row(:,p2:)
-      mat(:,:p1-1,p1) += tmp_row2(:,:p1-1)
-      mat(:,p1,p1:) += tmp_row2(:,p1:)
+      mat(:,:p2-1,p2) = mat(:,:p2-1,p2) + tmp_row(:,:p2-1)
+      mat(:,p2,p2:) = mat(:,p2,p2:) + tmp_row(:,p2:)
+      mat(:,:p1-1,p1) = mat(:,:p1-1,p1) + tmp_row2(:,:p1-1)
+      mat(:,p1,p1:) = mat(:,p1,p1:) + tmp_row2(:,p1:)
     end if
   end if
   deallocate(lbanned)
@@ -1765,7 +1763,7 @@ subroutine get_d1_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         if(bannedOrb(p1, s1) .or. bannedOrb(p2, s2) .or. banned(p1, p2, 1)) cycle
         call apply_particles(mask, s1, p1, s2, p2, det, ok, N_int)
         call i_h_j(gen, det, N_int, hij)
-        mat(:, p1, p2) += coefs(:) * hij
+        mat(:, p1, p2) = mat(:, p1, p2) + coefs(:) * hij
       end do
     end do
 end
@@ -1818,9 +1816,9 @@ subroutine get_d2_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
 
         hij = (mo_two_e_integral(p1, p2, h1, h2) - mo_two_e_integral(p2,p1, h1, h2)) * get_phase_bi(phasemask, ma, ma, h1, p1, h2, p2, N_int)
         if(ma == 1) then
-          mat(:, putj, puti) += coefs(:) * hij
+          mat(:, putj, puti) = mat(:, putj, puti) + coefs(:) * hij
         else
-          mat(:, puti, putj) += coefs(:) * hij
+          mat(:, puti, putj) = mat(:, puti, putj) + coefs(:) * hij
         end if
       end do
     else
@@ -1836,7 +1834,7 @@ subroutine get_d2_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
           p1 = p(turn2(i), 1)
 
           hij = mo_two_e_integral(p1, p2, h1, h2) * get_phase_bi(phasemask, 1, 2, h1, p1, h2, p2,N_int)
-          mat(:, puti, putj) += coefs(:) * hij
+          mat(:, puti, putj) = mat(:, puti, putj) + coefs(:) * hij
         end do
       end do
     end if
@@ -1856,7 +1854,7 @@ subroutine get_d2_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         p1 = p(i1, ma)
         p2 = p(i2, ma)
         hij = (mo_two_e_integral(p1, p2, h1, h2) - mo_two_e_integral(p2,p1, h1, h2)) * get_phase_bi(phasemask, ma, ma, h1, p1, h2, p2,N_int)
-        mat(:, puti, putj) += coefs(:) * hij
+        mat(:, puti, putj) = mat(:, puti, putj) + coefs(:) * hij
       end do
       end do
     else if(tip == 3) then
@@ -1870,7 +1868,7 @@ subroutine get_d2_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         p2 = p(i, ma)
 
         hij = mo_two_e_integral(p1, p2, h1, h2) * get_phase_bi(phasemask, mi, ma, h1, p1, h2, p2,N_int)
-        mat(:, min(puti, putj), max(puti, putj)) += coefs(:) * hij
+        mat(:, min(puti, putj), max(puti, putj)) = mat(:, min(puti, putj), max(puti, putj)) + coefs(:) * hij
       end do
     else ! tip == 4
       puti = p(1, sp)
@@ -1881,7 +1879,7 @@ subroutine get_d2_reference(gen, phasemask, bannedOrb, banned, mat, mask, h, p,
         h1 = h(1, mi)
         h2 = h(2, mi)
         hij = (mo_two_e_integral(p1, p2, h1, h2) - mo_two_e_integral(p2,p1, h1, h2)) * get_phase_bi(phasemask, mi, mi, h1, p1, h2, p2,N_int)
-        mat(:, puti, putj) += coefs(:) * hij
+        mat(:, puti, putj) = mat(:, puti, putj) + coefs(:) * hij
       end if
     end if
   end if
diff --git a/src/cipsi/stochastic_cipsi.irp.f b/src/cipsi/stochastic_cipsi.irp.f
index bd0c6a80..77c6ed48 100644
--- a/src/cipsi/stochastic_cipsi.irp.f
+++ b/src/cipsi/stochastic_cipsi.irp.f
@@ -104,7 +104,9 @@ subroutine run_stochastic_cipsi
 
     ! Add selected determinants
     call copy_H_apply_buffer_to_wf()
-!    call save_wavefunction
+    if (save_wf_after_selection) then
+      call save_wavefunction
+    endif
 
     PROVIDE  psi_coef
     PROVIDE  psi_det
diff --git a/src/davidson/davidson_parallel.irp.f b/src/davidson/davidson_parallel.irp.f
index 59318cd6..32f89979 100644
--- a/src/davidson/davidson_parallel.irp.f
+++ b/src/davidson/davidson_parallel.irp.f
@@ -428,7 +428,7 @@ subroutine H_S2_u_0_nstates_zmq(v_0,s_0,u_0,N_st,sze)
 
   integer :: istep, imin, imax, ishift, ipos
   integer, external :: add_task_to_taskserver
-  integer, parameter :: tasksize=10000
+  integer, parameter :: tasksize=20000
   character*(100000) :: task
   istep=1
   ishift=0
diff --git a/src/davidson/u0_h_u0.irp.f b/src/davidson/u0_h_u0.irp.f
index e56fdec4..bc6acdb9 100644
--- a/src/davidson/u0_h_u0.irp.f
+++ b/src/davidson/u0_h_u0.irp.f
@@ -211,6 +211,7 @@ subroutine H_S2_u_0_nstates_openmp_work_$N_int(v_t,s_t,u_t,N_st,sze,istart,iend,
   double precision               :: rss, mem, ratio
   double precision, allocatable  :: utl(:,:)
   integer, parameter             :: block_size=128
+  logical                        :: u_is_sparse
 
 !  call resident_memory(rss)
 !  mem = dble(singles_beta_csc_size) / 1024.d0**3
@@ -222,6 +223,7 @@ subroutine H_S2_u_0_nstates_openmp_work_$N_int(v_t,s_t,u_t,N_st,sze,istart,iend,
 !  endif
 compute_singles=.True.
 
+
   maxab = max(N_det_alpha_unique, N_det_beta_unique)+1
   allocate(idx0(maxab))
 
@@ -249,7 +251,7 @@ compute_singles=.True.
       !$OMP          singles_alpha_csc,singles_alpha_csc_idx,        &
       !$OMP          singles_beta_csc,singles_beta_csc_idx)          &
       !$OMP   PRIVATE(krow, kcol, tmp_det, spindet, k_a, k_b, i,     &
-      !$OMP          lcol, lrow, l_a, l_b, utl, kk,                  &
+      !$OMP          lcol, lrow, l_a, l_b, utl, kk, u_is_sparse,     &
       !$OMP          buffer, doubles, n_doubles, umax,               &
       !$OMP          tmp_det2, hij, sij, idx, l, kcol_prev,          &
       !$OMP          singles_a, n_singles_a, singles_b, ratio,       &
@@ -266,6 +268,22 @@ compute_singles=.True.
 
   kcol_prev=-1
 
+  ! Check if u has multiple zeros
+  kk=1 ! Avoid division by zero
+  !$OMP DO
+  do k=1,N_det
+    umax = 0.d0
+    do l=1,N_st
+      umax = max(umax, dabs(u_t(l,k)))
+    enddo
+    if (umax < 1.d-20) then
+      !$OMP ATOMIC
+      kk = kk+1
+    endif
+  enddo
+  !$OMP END DO
+  u_is_sparse = N_det / kk < 20  ! 5%
+
   ASSERT (iend <= N_det)
   ASSERT (istart > 0)
   ASSERT (istep  > 0)
@@ -405,16 +423,26 @@ compute_singles=.True.
       do k = 1,n_singles_a,block_size
         umax = 0.d0
         ! Prefetch u_t(:,l_a)
-        do kk=0,block_size-1
-          if (k+kk > n_singles_a) exit
-          l_a = singles_a(k+kk)
-          ASSERT (l_a <= N_det)
+        if (u_is_sparse) then
+          do kk=0,block_size-1
+            if (k+kk > n_singles_a) exit
+            l_a = singles_a(k+kk)
+            ASSERT (l_a <= N_det)
 
-          do l=1,N_st
-            utl(l,kk+1) = u_t(l,l_a)
-            umax = max(umax, dabs(utl(l,kk+1)))
+            do l=1,N_st
+              utl(l,kk+1) = u_t(l,l_a)
+              umax = max(umax, dabs(utl(l,kk+1)))
+            enddo
           enddo
-        enddo
+        else
+          do kk=0,block_size-1
+            if (k+kk > n_singles_a) exit
+            l_a = singles_a(k+kk)
+            ASSERT (l_a <= N_det)
+            utl(:,kk+1) = u_t(:,l_a)
+          enddo
+          umax = 1.d0
+        endif
         if (umax < 1.d-20) cycle
 
         do kk=0,block_size-1
@@ -497,16 +525,26 @@ compute_singles=.True.
     do i=1,n_singles_a,block_size
       umax = 0.d0
       ! Prefetch u_t(:,l_a)
-      do kk=0,block_size-1
-        if (i+kk > n_singles_a) exit
-        l_a = singles_a(i+kk)
-        ASSERT (l_a <= N_det)
+      if (u_is_sparse) then
+        do kk=0,block_size-1
+          if (i+kk > n_singles_a) exit
+          l_a = singles_a(i+kk)
+          ASSERT (l_a <= N_det)
 
-        do l=1,N_st
-          utl(l,kk+1) = u_t(l,l_a)
-          umax = max(umax, dabs(utl(l,kk+1)))
+          do l=1,N_st
+            utl(l,kk+1) = u_t(l,l_a)
+            umax = max(umax, dabs(utl(l,kk+1)))
+          enddo
         enddo
-      enddo
+      else
+        do kk=0,block_size-1
+          if (i+kk > n_singles_a) exit
+          l_a = singles_a(i+kk)
+          ASSERT (l_a <= N_det)
+          utl(:,kk+1) = u_t(:,l_a)
+        enddo
+        umax = 1.d0
+      endif
       if (umax < 1.d-20) cycle
 
       do kk=0,block_size-1
@@ -534,16 +572,26 @@ compute_singles=.True.
     do i=1,n_doubles,block_size
       umax = 0.d0
       ! Prefetch u_t(:,l_a)
-      do kk=0,block_size-1
-        if (i+kk > n_doubles) exit
-        l_a = doubles(i+kk)
-        ASSERT (l_a <= N_det)
+      if (u_is_sparse) then
+        do kk=0,block_size-1
+          if (i+kk > n_doubles) exit
+          l_a = doubles(i+kk)
+          ASSERT (l_a <= N_det)
 
-        do l=1,N_st
-          utl(l,kk+1) = u_t(l,l_a)
-          umax = max(umax, dabs(utl(l,kk+1)))
+          do l=1,N_st
+            utl(l,kk+1) = u_t(l,l_a)
+            umax = max(umax, dabs(utl(l,kk+1)))
+          enddo
         enddo
-      enddo
+      else
+        do kk=0,block_size-1
+          if (i+kk > n_doubles) exit
+          l_a = doubles(i+kk)
+          ASSERT (l_a <= N_det)
+          utl(:,kk+1) = u_t(:,l_a)
+        enddo
+        umax = 1.d0
+      endif
       if (umax < 1.d-20) cycle
 
       do kk=0,block_size-1
@@ -611,19 +659,30 @@ compute_singles=.True.
     !DIR$ LOOP COUNT avg(1000)
     do i=1,n_singles_b,block_size
       umax = 0.d0
-      do kk=0,block_size-1
-        if (i+kk > n_singles_b) exit
-        l_b = singles_b(i+kk)
-        ASSERT (l_b <= N_det)
+      if (u_is_sparse) then
+        do kk=0,block_size-1
+          if (i+kk > n_singles_b) exit
+          l_b = singles_b(i+kk)
+          l_a = psi_bilinear_matrix_transp_order(l_b)
+          ASSERT (l_b <= N_det)
+          ASSERT (l_a <= N_det)
 
-        l_a = psi_bilinear_matrix_transp_order(l_b)
-        ASSERT (l_a <= N_det)
-
-        do l=1,N_st
-          utl(l,kk+1) = u_t(l,l_a)
-          umax = max(umax, dabs(utl(l,kk+1)))
+          do l=1,N_st
+            utl(l,kk+1) = u_t(l,l_a)
+            umax = max(umax, dabs(utl(l,kk+1)))
+          enddo
         enddo
-      enddo
+      else
+        do kk=0,block_size-1
+          if (i+kk > n_singles_b) exit
+          l_b = singles_b(i+kk)
+          l_a = psi_bilinear_matrix_transp_order(l_b)
+          ASSERT (l_b <= N_det)
+          ASSERT (l_a <= N_det)
+          utl(:,kk+1) = u_t(:,l_a)
+        enddo
+        umax = 1.d0
+      endif
       if (umax < 1.d-20) cycle
 
       do kk=0,block_size-1
@@ -649,18 +708,29 @@ compute_singles=.True.
     !DIR$ LOOP COUNT avg(50000)
     do i=1,n_doubles,block_size
       umax = 0.d0
-      do kk=0,block_size-1
-        if (i+kk > n_doubles) exit
-        l_b = doubles(i+kk)
-        ASSERT (l_b <= N_det)
-        l_a = psi_bilinear_matrix_transp_order(l_b)
-        ASSERT (l_a <= N_det)
-
-        do l=1,N_st
-          utl(l,kk+1) = u_t(l,l_a)
-          umax = max(umax, dabs(utl(l,kk+1)))
+      if (u_is_sparse) then
+        do kk=0,block_size-1
+          if (i+kk > n_doubles) exit
+          l_b = doubles(i+kk)
+          l_a = psi_bilinear_matrix_transp_order(l_b)
+          ASSERT (l_b <= N_det)
+          ASSERT (l_a <= N_det)
+          do l=1,N_st
+            utl(l,kk+1) = u_t(l,l_a)
+            umax = max(umax, dabs(utl(l,kk+1)))
+          enddo
         enddo
-      enddo
+      else
+        do kk=0,block_size-1
+          if (i+kk > n_doubles) exit
+          l_b = doubles(i+kk)
+          l_a = psi_bilinear_matrix_transp_order(l_b)
+          ASSERT (l_b <= N_det)
+          ASSERT (l_a <= N_det)
+          utl(:,kk+1) = u_t(:,l_a)
+        enddo
+        umax = 1.d0
+      endif
       if (umax < 1.d-20) cycle
 
       do kk=0,block_size-1
@@ -688,10 +758,14 @@ compute_singles=.True.
     ! Initial determinant is at k_a in alpha-major representation
     ! -----------------------------------------------------------------------
 
-    umax = 0.d0
-    do l=1,N_st
-      umax = max(umax, dabs(u_t(l,k_a)))
-    enddo
+    if (u_is_sparse) then
+      umax = 0.d0
+      do l=1,N_st
+        umax = max(umax, dabs(u_t(l,k_a)))
+      enddo
+    else
+      umax = 1.d0
+    endif
     if (umax < 1.d-20) cycle
 
     krow = psi_bilinear_matrix_rows(k_a)
diff --git a/src/determinants/configurations.irp.f b/src/determinants/configurations.irp.f
index 2c141609..1baa35b6 100644
--- a/src/determinants/configurations.irp.f
+++ b/src/determinants/configurations.irp.f
@@ -42,6 +42,7 @@ subroutine configuration_to_dets_size(o,sze,n_alpha,Nint)
     amax -= popcnt( o(k,2) )
   enddo
   if (binom_int(bmax, amax) > huge(1)) then
+    print *, bmax, amax
     print *,  irp_here, ': Too many determinants to generate'
     stop 1
   endif
@@ -340,7 +341,7 @@ BEGIN_PROVIDER [ integer, det_to_configuration, (N_det) ]
  ! Returns the index of the configuration for each determinant
  END_DOC
  integer :: i,j,k,r,l
- integer*8 :: key
+ integer*8 :: key, key2
  integer(bit_kind) :: occ(N_int,2)
  logical :: found
  integer*8, allocatable :: bit_tmp(:)
@@ -361,36 +362,23 @@ BEGIN_PROVIDER [ integer, det_to_configuration, (N_det) ]
 
     key = configuration_search_key(occ,N_int)
 
-    ! TODO: Binary search
-    l = 1
-    r = N_configuration
-!    do while(r-l > 32)
-!      j = shiftr(r+l,1)
-!      if (bit_tmp(j) < key) then
-!        l = j
-!      else
-!        r = j
-!      endif
-!    enddo
-    do j=l,r
-      found = .True.
-      do k=1,N_int
-        if ( (occ(k,1) /= psi_configuration(k,1,j)) &
-        .or. (occ(k,2) /= psi_configuration(k,2,j)) ) then
-          found = .False.
-          exit
-        endif
-      enddo
-      if (found) then
+    l = 0
+    r = N_configuration+1
+    j = shiftr(r-l,1)
+    do while (j>=1)
+      j = j+l
+      key2 = configuration_search_key(psi_configuration(1,1,j),N_int)
+      if (key2 == key) then
         det_to_configuration(i) = j
         exit
+      else if (key2 > key) then
+        r = j
+      else
+        l = j
       endif
+      j = shiftr(r-l,1)
     enddo
 
-    if (.not.found) then
-      print *,  '3 bug in ',  irp_here
-      stop -1
-    endif
  enddo
  !$OMP END PARALLEL DO
  deallocate(bit_tmp)
diff --git a/src/mo_two_e_ints/map_integrals.irp.f b/src/mo_two_e_ints/map_integrals.irp.f
index 354dd994..8756ee47 100644
--- a/src/mo_two_e_ints/map_integrals.irp.f
+++ b/src/mo_two_e_ints/map_integrals.irp.f
@@ -99,9 +99,15 @@ double precision function get_two_e_integral(i,j,k,l,map)
   type(map_type), intent(inout)  :: map
   real(integral_kind)            :: tmp
   PROVIDE mo_two_e_integrals_in_map mo_integrals_cache
-  if (banned_excitation(i,k) .or. banned_excitation(j,l)) then
-    get_two_e_integral = 0.d0
-    return
+  if (use_banned_excitation) then
+    if (banned_excitation(i,k)) then
+      get_two_e_integral = 0.d0
+      return
+    endif
+    if (banned_excitation(j,l)) then
+      get_two_e_integral = 0.d0
+      return
+    endif
   endif
   ii = l-mo_integrals_cache_min
   ii = ior(ii, k-mo_integrals_cache_min)
@@ -282,17 +288,19 @@ subroutine get_mo_two_e_integrals_exch_ii(k,l,sze,out_val,map)
 
 end
 
-BEGIN_PROVIDER [ logical, banned_excitation, (mo_num,mo_num) ]
+ BEGIN_PROVIDER [ logical, banned_excitation, (mo_num,mo_num) ]
+&BEGIN_PROVIDER [ logical, use_banned_excitation  ]
  implicit none
  use map_module
  BEGIN_DOC
  ! If true, the excitation is banned in the selection. Useful with local MOs.
  END_DOC
  banned_excitation = .False.
- integer :: i,j
+ integer :: i,j, icount
  integer(key_kind)              :: idx
  double precision :: tmp
-! double precision :: buffer(mo_num)
+
+ icount = 1 ! Avoid division by zero
  do j=1,mo_num
    do i=1,j-1
     call two_e_integrals_index(i,j,j,i,idx)
@@ -300,8 +308,14 @@ BEGIN_PROVIDER [ logical, banned_excitation, (mo_num,mo_num) ]
     call map_get(mo_integrals_map,idx,tmp)
     banned_excitation(i,j) = dabs(tmp) < 1.d-14
     banned_excitation(j,i) = banned_excitation(i,j)
+    if (banned_excitation(i,j)) icount = icount+2
   enddo
  enddo
+ use_banned_excitation =  (mo_num*mo_num) / icount <= 100  !1%
+ if (use_banned_excitation) then
+   print *, 'Using sparsity of exchange integrals'
+ endif
+
 END_PROVIDER
 
 
diff --git a/src/two_body_rdm/example.irp.f b/src/two_body_rdm/example.irp.f
index 4400613c..e9cbd1a2 100644
--- a/src/two_body_rdm/example.irp.f
+++ b/src/two_body_rdm/example.irp.f
@@ -284,3 +284,4 @@ subroutine routine_full_mos
    print*,'wee_tot_st_av_3         = ',wee_tot_st_av_3
 
 end
+
diff --git a/travis/compilation.sh b/travis/compilation.sh
index 1aa26dda..071b4872 100755
--- a/travis/compilation.sh
+++ b/travis/compilation.sh
@@ -8,7 +8,7 @@ tar -zxf $HOME/cache/config.tgz
 # Configure QP2
 cd qp2
 source ./quantum_package.rc
-ninja -j 1 -v
+ninja -j 1 -v || exit -1
 
 # Create cache
 cd ..
diff --git a/travis/configuration.sh b/travis/configuration.sh
index fa52e793..7b3f5423 100755
--- a/travis/configuration.sh
+++ b/travis/configuration.sh
@@ -2,7 +2,7 @@
 # Stage 1
 
 # Configure QP2
-./configure --install all --config ./config/travis.cfg
+./configure --install all --config ./config/travis.cfg || exit -1
 
 # Create cache
 cd ../
diff --git a/travis/testing.sh b/travis/testing.sh
index b2122f5c..f67bd106 100755
--- a/travis/testing.sh
+++ b/travis/testing.sh
@@ -8,7 +8,7 @@ tar -zxf $HOME/cache/compil.tgz
 # Configure QP2
 cd qp2
 source ./quantum_package.rc
-qp_test -a && rm $HOME/cache/compil.tgz
+exec qp_test -a && rm $HOME/cache/compil.tgz