diff --git a/.drone.yml b/.drone.yml
new file mode 100644
index 00000000..b213de7b
--- /dev/null
+++ b/.drone.yml
@@ -0,0 +1,28 @@
+---
+kind: pipeline
+type: docker
+name: default
+
+clone:
+  depth: 10
+
+steps:
+
+- name: configure
+  image: scemama666/qp2_env
+  commands:
+  - ./configure -i all -c ./config/gfortran_debug.cfg
+  - bash -c "source quantum_package.rc ; qp plugins download https://gitlab.com/scemama/qp_plugins_scemama"
+  - bash -c "source quantum_package.rc ; qp plugins install champ"
+
+- name: compile
+  image: scemama666/qp2_env
+  commands:
+  - bash -c "source quantum_package.rc ; exec ninja"
+
+- name: testing
+  image: scemama666/qp2_env
+  commands:
+  - bash -c "source quantum_package.rc ; qp test -a"
+
+
diff --git a/drone/Docker/README.md b/drone/Docker/README.md
new file mode 100644
index 00000000..eb569777
--- /dev/null
+++ b/drone/Docker/README.md
@@ -0,0 +1,8 @@
+Docker files to build the containers used with DroneCI.
+
+Example:
+```
+docker build -t ubuntu/qp2_env .
+
+```
+
diff --git a/drone/Docker/Ubuntu/Dockerfile b/drone/Docker/Ubuntu/Dockerfile
new file mode 100644
index 00000000..05d87ad8
--- /dev/null
+++ b/drone/Docker/Ubuntu/Dockerfile
@@ -0,0 +1,27 @@
+ARG UBUNTU_VERSION=20.04
+FROM ubuntu:${UBUNTU_VERSION} AS builder
+
+# Timezone for tzdata
+ARG tz=Etc/UTC
+RUN echo $tz > /etc/timezone && rm -rf /etc/localtime
+
+# Install
+RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y \
+ git \
+ curl \
+ wget \
+ python3 \
+ gfortran \
+ gcc \
+ g++ \
+ make \
+ build-essential \
+ rsync \
+ unzip \
+ libopenblas-dev \
+ pkg-config \
+ m4
+
+RUN ln -s /usr/bin/python3 /usr/bin/python
+
+
diff --git a/travis/compilation.sh b/drone/compilation.sh
similarity index 100%
rename from travis/compilation.sh
rename to drone/compilation.sh
diff --git a/travis/configuration.sh b/drone/configuration.sh
similarity index 100%
rename from travis/configuration.sh
rename to drone/configuration.sh
diff --git a/drone/drone_docker.yml b/drone/drone_docker.yml
new file mode 100644
index 00000000..d1eb7175
--- /dev/null
+++ b/drone/drone_docker.yml
@@ -0,0 +1,30 @@
+---
+kind: pipeline
+type: docker
+name: default
+
+clone:
+  depth: 10
+
+steps:
+- name: configure
+  pull: never
+  image: ubuntu/qp2_env
+  commands:
+  - ./configure -i all -c ./config/gfortran_debug.cfg
+  - source quantum_package.rc ; qp plugins download https://gitlab.com/scemama/qp_plugins_scemama
+  - source quantum_package.rc ; qp plugins install champ
+
+- name: compile
+  pull: never
+  image: ubuntu/qp2_env
+  commands:
+  - ninja
+
+- name: testing
+  pull: never
+  image: ubuntu/qp2_env
+  commands:
+  - qp test
+
+
diff --git a/drone/drone_ssh.yml b/drone/drone_ssh.yml
new file mode 100644
index 00000000..99397f11
--- /dev/null
+++ b/drone/drone_ssh.yml
@@ -0,0 +1,29 @@
+kind: pipeline
+type: ssh
+name: default
+
+clone:
+  depth: 10
+
+server:
+  host: 130.120.229.139
+  user: test
+  password:
+        from_secret: ssh_pass
+
+steps:
+- name: configure
+  commands:
+  - ./configure -i all -c ./config/gfortran_debug.cfg
+  - source quantum_package.rc ; qp plugins download https://gitlab.com/scemama/qp_plugins_scemama
+  - source quantum_package.rc ; qp plugins install champ
+
+- name: compile
+  commands:
+  - ninja
+
+- name: testing
+  commands:
+  - qp test
+
+
diff --git a/travis/testing.sh b/drone/testing.sh
similarity index 100%
rename from travis/testing.sh
rename to drone/testing.sh
diff --git a/src/cipsi/EZFIO.cfg b/src/cipsi/EZFIO.cfg
index 7fcf19eb..e01359c5 100644
--- a/src/cipsi/EZFIO.cfg
+++ b/src/cipsi/EZFIO.cfg
@@ -34,3 +34,9 @@ doc: Maximum number of excitation for beta determinants with respect to the Hart
 interface: ezfio,ocaml,provider
 default: -1
 
+[twice_hierarchy_max]
+type: integer
+doc: Twice the maximum hierarchy parameter (excitation degree plus half the seniority number). Using -1 selects all determinants
+interface: ezfio,ocaml,provider
+default: -1
+
diff --git a/src/cipsi/selection.irp.f b/src/cipsi/selection.irp.f
index 342f759f..7417dd05 100644
--- a/src/cipsi/selection.irp.f
+++ b/src/cipsi/selection.irp.f
@@ -713,6 +713,25 @@ subroutine fill_buffer_double(i_generator, sp, h1, h2, bannedOrb, banned, fock_d
         if (do_cycle) cycle
       endif
 
+      if (twice_hierarchy_max >= 0) then
+        s = 0
+        do k=1,N_int
+          s = s + popcnt(ieor(det(k,1),det(k,2)))
+        enddo
+        if ( mod(s,2)>0 ) stop 'For now, hierarchy CI is defined only for an even number of electrons'
+        if (excitation_ref == 1) then
+          call get_excitation_degree(HF_bitmask,det(1,1),degree,N_int)
+        else if (excitation_ref == 2) then
+          stop 'For now, hierarchy CI is defined only for a single reference determinant'
+!         do k=1,N_dominant_dets_of_cfgs
+!           call get_excitation_degree(dominant_dets_of_cfgs(1,1,k),det(1,1),degree,N_int)
+!         enddo
+        endif
+        integer :: twice_hierarchy
+        twice_hierarchy = degree + s/2
+        if (twice_hierarchy > twice_hierarchy_max) cycle
+      endif
+
       Hii = diag_H_mat_elem_fock(psi_det_generators(1,1,i_generator),det,fock_diag_tmp,N_int)
 
       w = 0d0
diff --git a/src/fci/40.fci.bats b/src/fci/40.fci.bats
index f2c78067..1a0c5507 100644
--- a/src/fci/40.fci.bats
+++ b/src/fci/40.fci.bats
@@ -59,43 +59,43 @@ function run_stoch() {
 
 @test "HCO" { # 12.2868s
   qp set_file hco.ezfio
-  run -113.389297812482 6.e-4  100000
+  run -113.393356604085 1.e-3  100000
 }
 
 @test "H2O2" { # 12.9214s
   qp set_file h2o2.ezfio
   qp set_mo_class --core="[1-2]" --act="[3-24]" --del="[25-38]"
-  run -151.00467 1.e-4  100000
+  run -151.005848404095 1.e-3  100000
 }
 
 @test "HBO" { # 13.3144s
   [[ -n $TRAVIS ]] && skip
   qp set_file hbo.ezfio
-  run -100.212560384678 1.e-3  100000
+  run -100.214099486337 1.e-3  100000
 }
 
 @test "H2O" { # 11.3727s
   [[ -n $TRAVIS ]] && skip
   qp set_file h2o.ezfio
-  run -76.2361605151999 3.e-4  100000
+  run -76.2361605151999 5.e-4  100000
 }
 
 @test "ClO" { # 13.3755s
   [[ -n $TRAVIS ]] && skip
   qp set_file clo.ezfio
-  run -534.545616787223 3.e-4  100000
+  run -534.546453546852 1.e-3  100000
 }
 
 @test "SO" { # 13.4952s
   [[ -n $TRAVIS ]] && skip
   qp set_file so.ezfio
-  run -26.0096209515081 1.e-3  100000
+  run -26.0176563764039 1.e-3  100000
 }
 
 @test "H2S" { # 13.6745s
   [[ -n $TRAVIS ]] && skip
   qp set_file h2s.ezfio
-  run -398.859168655255 3.e-4  100000
+  run -398.859577605891 5.e-4  100000
 }
 
 @test "OH" { # 13.865s
@@ -113,13 +113,13 @@ function run_stoch() {
 @test "H3COH" { # 14.7299s
   [[ -n $TRAVIS ]] && skip
   qp set_file h3coh.ezfio
-  run -115.205191406072 3.e-4  100000
+  run -115.205632960026 1.e-3  100000
 }
 
 @test "SiH3" { # 15.99s
   [[ -n $TRAVIS ]] && skip
   qp set_file sih3.ezfio
-  run -5.57241217753818 3.e-4   100000
+  run -5.57241217753818 5.e-4   100000
 }
 
 @test "CH4" { # 16.1612s
@@ -132,28 +132,28 @@ function run_stoch() {
 @test "ClF" { # 16.8864s
   [[ -n $TRAVIS ]] && skip
   qp set_file clf.ezfio
-  run -559.169313755572 3.e-4  100000
+  run -559.169748890031 1.5e-3  100000
 }
 
 @test "SO2" { # 17.5645s
   [[ -n $TRAVIS ]] && skip
   qp set_file so2.ezfio
   qp set_mo_class --core="[1-8]" --act="[9-87]"
-  run -41.5746738713298 3.e-4  100000
+  run -41.5746738713298 1.5e-3  100000
 }
 
 @test "C2H2" { # 17.6827s
   [[ -n $TRAVIS ]] && skip
   qp set_file c2h2.ezfio
   qp set_mo_class --act="[1-30]" --del="[31-36]"
-  run -12.3685464085969 3.e-4  100000
+  run -12.3685464085969 2.e-3  100000
 }
 
 @test "N2" { # 18.0198s
   [[ -n $TRAVIS ]] && skip
   qp set_file n2.ezfio
   qp set_mo_class --core="[1,2]" --act="[3-40]" --del="[41-60]"
-  run -109.28681540699360 3.e-4  100000
+  run -109.287917088107   1.5e-3  100000
 }
 
 @test "N2H4" { # 18.5006s
@@ -167,7 +167,7 @@ function run_stoch() {
   [[ -n $TRAVIS ]] && skip
   qp set_file co2.ezfio
   qp set_mo_class --core="[1,2]" --act="[3-30]" --del="[31-42]"
-  run -187.968547952413 3.e-4  100000
+  run -187.970184372047 1.5e-3  100000
 }
 
 
@@ -182,6 +182,6 @@ function run_stoch() {
   [[ -n $TRAVIS ]] && skip
   qp set_file hcn.ezfio
   qp set_mo_class --core="[1,2]" --act="[3-40]" --del="[41-55]"
-  run -93.0771143355433 3.e-4  100000
+  run -93.0777619629755 1.e-3  100000
 }