diff --git a/c++/triqs_tprf/lattice/fourier.hpp b/c++/triqs_tprf/lattice/fourier.hpp
index b135d135..16e7b17d 100644
--- a/c++/triqs_tprf/lattice/fourier.hpp
+++ b/c++/triqs_tprf/lattice/fourier.hpp
@@ -34,7 +34,7 @@ namespace triqs_tprf {
   }
 
 template <typename Gf_type>
-auto fourier_wr_to_tr_general_target(Gf_type g_wr, int n_tau = -1) {
+auto fourier_wr_to_tr_general_target(Gf_type g_wr, int n_tau = -1, mpi::communicator const &c = {}) {
 
   auto _ = all_t{};
   // Get rid of structured binding declarations in this file due to issue #11
@@ -48,7 +48,7 @@ auto fourier_wr_to_tr_general_target(Gf_type g_wr, int n_tau = -1) {
   auto r0 = *rmesh.begin();
   auto p = _fourier_plan<0>(gf_const_view(g_wr[_, r0]), gf_view(g_tr[_, r0]));
 
-  auto r_arr = mpi_view(rmesh);
+  auto r_arr = mpi_view(rmesh, c);
 
 #pragma omp parallel for 
   for (unsigned int idx = 0; idx < r_arr.size(); idx++) {
@@ -63,12 +63,12 @@ auto fourier_wr_to_tr_general_target(Gf_type g_wr, int n_tau = -1) {
 
     g_tr[_, r] = g_t;
   }
-  g_tr = mpi::all_reduce(g_tr);
+  g_tr = mpi::all_reduce(g_tr, c);
   return g_tr;
 }
 
 template <typename Gf_type>
-auto fourier_tr_to_wr_general_target(Gf_type g_tr, int n_w = -1) {
+auto fourier_tr_to_wr_general_target(Gf_type g_tr, int n_w = -1, mpi::communicator const &c = {}) {
   
   auto _ = all_t{};
   //auto [tmesh, rmesh] = g_tr.mesh();
@@ -81,7 +81,7 @@ auto fourier_tr_to_wr_general_target(Gf_type g_tr, int n_w = -1) {
   auto r0 = *rmesh.begin();
   auto p = _fourier_plan<0>(gf_const_view(g_tr[_, r0]), gf_view(g_wr[_, r0]));
 
-  auto r_arr = mpi_view(rmesh);
+  auto r_arr = mpi_view(rmesh, c);
 
 #pragma omp parallel for 
   for (unsigned int idx = 0; idx < r_arr.size(); idx++) {
@@ -96,12 +96,12 @@ auto fourier_tr_to_wr_general_target(Gf_type g_tr, int n_w = -1) {
 
     g_wr[_, r] = g_w;
   }
-  g_wr = mpi::all_reduce(g_wr);
+  g_wr = mpi::all_reduce(g_wr, c);
   return g_wr;
 }
 
 template <typename Gf_type>
-auto fourier_wk_to_wr_general_target(Gf_type g_wk) {
+auto fourier_wk_to_wr_general_target(Gf_type g_wk, mpi::communicator const &c = {}) {
   
   auto _ = all_t{};
 
@@ -116,7 +116,7 @@ auto fourier_wk_to_wr_general_target(Gf_type g_wk) {
   auto w0 = *wmesh.begin();
   auto p = _fourier_plan<0>(gf_const_view(g_wk[w0, _]), gf_view(g_wr[w0, _]));
 
-  auto w_arr = mpi_view(wmesh);
+  auto w_arr = mpi_view(wmesh, c);
 
 #pragma omp parallel for 
   for (unsigned int idx = 0; idx < w_arr.size(); idx++) {
@@ -131,12 +131,12 @@ auto fourier_wk_to_wr_general_target(Gf_type g_wk) {
 
     g_wr[w, _] = g_r;
   }
-  g_wr = mpi::all_reduce(g_wr);
+  g_wr = mpi::all_reduce(g_wr, c);
   return g_wr;
 }
 
 template <typename Gf_type>
-auto fourier_wr_to_wk_general_target(Gf_type g_wr) {
+auto fourier_wr_to_wk_general_target(Gf_type g_wr, mpi::communicator const &c = {}) {
   
   auto _ = all_t{};
 
@@ -150,7 +150,7 @@ auto fourier_wr_to_wk_general_target(Gf_type g_wr) {
   auto w0 = *wmesh.begin();
   auto p = _fourier_plan<0>(gf_const_view(g_wr[w0, _]), gf_view(g_wk[w0, _]));
 
-  auto w_arr = mpi_view(wmesh);
+  auto w_arr = mpi_view(wmesh, c);
 
 #pragma omp parallel for 
   for (unsigned int idx = 0; idx < w_arr.size(); idx++) {
@@ -165,7 +165,7 @@ auto fourier_wr_to_wk_general_target(Gf_type g_wr) {
 
     g_wk[w, _] = g_k;
   }
-  g_wk = mpi::all_reduce(g_wk);
+  g_wk = mpi::all_reduce(g_wk, c);
   return g_wk;
 }
 
diff --git a/c++/triqs_tprf/lattice/gf.cpp b/c++/triqs_tprf/lattice/gf.cpp
index 7274ba86..b51f423d 100644
--- a/c++/triqs_tprf/lattice/gf.cpp
+++ b/c++/triqs_tprf/lattice/gf.cpp
@@ -38,13 +38,13 @@ namespace triqs_tprf {
 // ----------------------------------------------------
 // g
 
-g_wk_t lattice_dyson_g0_wk(double mu, e_k_cvt e_k, gf_mesh<imfreq> mesh) {
+g_wk_t lattice_dyson_g0_wk(double mu, e_k_cvt e_k, gf_mesh<imfreq> mesh, mpi::communicator const &c) {
 
   auto I = nda::eye<ek_vt::scalar_t>(e_k.target_shape()[0]);
   g_wk_t g0_wk({mesh, e_k.mesh()}, e_k.target_shape());
   g0_wk() = 0.0;
 
-  auto arr = mpi_view(g0_wk.mesh());
+  auto arr = mpi_view(g0_wk.mesh(), c);
 
 #pragma omp parallel for
   for (unsigned int idx = 0; idx < arr.size(); idx++) {
@@ -52,14 +52,14 @@ g_wk_t lattice_dyson_g0_wk(double mu, e_k_cvt e_k, gf_mesh<imfreq> mesh) {
     g0_wk[w, k] = inverse((w + mu)*I - e_k(k));      
   }
 
-  g0_wk = mpi::all_reduce(g0_wk);
+  g0_wk = mpi::all_reduce(g0_wk, c);
   return g0_wk;
 }
 
 // ----------------------------------------------------
 
 template<typename sigma_t>
-auto lattice_dyson_g_generic(double mu, e_k_cvt e_k, sigma_t sigma){
+auto lattice_dyson_g_generic(double mu, e_k_cvt e_k, sigma_t sigma, mpi::communicator const &c){
 
   auto &freqmesh = [&sigma]() -> auto & {
     if constexpr (sigma_t::arity == 1) return sigma.mesh();
@@ -72,7 +72,7 @@ auto lattice_dyson_g_generic(double mu, e_k_cvt e_k, sigma_t sigma){
   g_wk_t g_wk({freqmesh, e_k.mesh()}, e_k.target_shape());
   g_wk() = 0.0;
 
-  auto arr = mpi_view(g_wk.mesh());
+  auto arr = mpi_view(g_wk.mesh(), c);
 #pragma omp parallel for
   for (unsigned int idx = 0; idx < arr.size(); idx++) {
     auto &[w, k] = arr(idx);
@@ -84,33 +84,33 @@ auto lattice_dyson_g_generic(double mu, e_k_cvt e_k, sigma_t sigma){
     g_wk[w, k] = inverse((w + mu)*I - e_k(k) - sigmaterm);
   }
 
-  g_wk = mpi::all_reduce(g_wk);
+  g_wk = mpi::all_reduce(g_wk, c);
   return g_wk;
 }
 
 
-g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_wk_cvt sigma_wk) {
-  return lattice_dyson_g_generic(mu, e_k, sigma_wk);
+g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_wk_cvt sigma_wk, mpi::communicator const &c) {
+  return lattice_dyson_g_generic(mu, e_k, sigma_wk, c);
 }
   
 
-g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_w_cvt sigma_w) {
-  return lattice_dyson_g_generic(mu, e_k, sigma_w);
+g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_w_cvt sigma_w, mpi::communicator const &c) {
+  return lattice_dyson_g_generic(mu, e_k, sigma_w, c);
 }
 
 
-g_w_t lattice_dyson_g_w(double mu, e_k_cvt e_k, g_w_cvt sigma_w) {
+g_w_t lattice_dyson_g_w(double mu, e_k_cvt e_k, g_w_cvt sigma_w, mpi::communicator const &c) {
 
-  auto g_wk = lattice_dyson_g_generic(mu, e_k, sigma_w);
+  auto g_wk = lattice_dyson_g_generic(mu, e_k, sigma_w, c);
   auto &[wmesh, kmesh] = g_wk.mesh();
 
   g_w_t g_w(wmesh, e_k.target_shape());
   g_w() = 0.0;
 
-  for (auto const &[w, k] : mpi_view(g_wk.mesh())) 
+  for (auto const &[w, k] : mpi_view(g_wk.mesh(), c))
     g_w[w] += g_wk[w, k];
 
-  g_w = mpi::all_reduce(g_w);
+  g_w = mpi::all_reduce(g_w, c);
   g_w /= kmesh.size();
   return g_w;
 }
@@ -118,26 +118,26 @@ g_w_t lattice_dyson_g_w(double mu, e_k_cvt e_k, g_w_cvt sigma_w) {
 // ----------------------------------------------------
 // Transformations: real space <-> reciprocal space 
   
-g_wr_t fourier_wk_to_wr(g_wk_cvt g_wk) {
-  auto g_wr = fourier_wk_to_wr_general_target(g_wk);
+g_wr_t fourier_wk_to_wr(g_wk_cvt g_wk, mpi::communicator const &c) {
+  auto g_wr = fourier_wk_to_wr_general_target(g_wk, c);
   return g_wr;
 }
 
-g_wk_t fourier_wr_to_wk(g_wr_cvt g_wr) {
-  auto g_wk = fourier_wr_to_wk_general_target(g_wr);
+g_wk_t fourier_wr_to_wk(g_wr_cvt g_wr, mpi::communicator const &c) {
+  auto g_wk = fourier_wr_to_wk_general_target(g_wr, c);
   return g_wk;
 }
 
 // ----------------------------------------------------
 // Transformations: Matsubara frequency <-> imaginary time
 
-g_wr_t fourier_tr_to_wr(g_tr_cvt g_tr, int nw) {
-  auto g_wr = fourier_tr_to_wr_general_target(g_tr, nw);
+g_wr_t fourier_tr_to_wr(g_tr_cvt g_tr, int nw, mpi::communicator const &c) {
+  auto g_wr = fourier_tr_to_wr_general_target(g_tr, nw, c);
   return g_wr;
 }
 
-g_tr_t fourier_wr_to_tr(g_wr_cvt g_wr, int nt) {
-  auto g_tr = fourier_wr_to_tr_general_target(g_wr, nt);
+g_tr_t fourier_wr_to_tr(g_wr_cvt g_wr, int nt, mpi::communicator const &c) {
+  auto g_tr = fourier_wr_to_tr_general_target(g_wr, nt, c);
   return g_tr;
 }
 
diff --git a/c++/triqs_tprf/lattice/gf.hpp b/c++/triqs_tprf/lattice/gf.hpp
index ec0f7b8e..7d7861cc 100644
--- a/c++/triqs_tprf/lattice/gf.hpp
+++ b/c++/triqs_tprf/lattice/gf.hpp
@@ -41,7 +41,7 @@ namespace triqs_tprf {
   @param mesh imaginary frequency mesh
   @return Matsubara frequency lattice Green's function $G^{(0)}_{a\bar{b}}(i\omega_n, \mathbf{k})$
 */
-g_wk_t lattice_dyson_g0_wk(double mu, e_k_cvt e_k, mesh::imfreq mesh);
+g_wk_t lattice_dyson_g0_wk(double mu, e_k_cvt e_k, mesh::imfreq mesh, mpi::communicator const &c = {});
 
 /** Construct an interacting Matsubara frequency lattice Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{k})`
    
@@ -61,7 +61,7 @@ g_wk_t lattice_dyson_g0_wk(double mu, e_k_cvt e_k, mesh::imfreq mesh);
  @param sigma_w imaginary frequency self-energy :math:`\Sigma_{\bar{a}b}(i\omega_n)`
  @return Matsubara frequency lattice Green's function $G_{a\bar{b}}(i\omega_n, \mathbf{k})$
  */
-g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_w_cvt sigma_w);
+g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_w_cvt sigma_w, mpi::communicator const &c = {});
 
 /** Construct an interacting Matsubara frequency lattice Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{k})`
    
@@ -81,7 +81,7 @@ g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_w_cvt sigma_w);
  @param sigma_wk imaginary frequency self-energy :math:`\Sigma_{\bar{a}b}(i\omega_n, \mathbf{k})`
  @return Matsubara frequency lattice Green's function $G_{a\bar{b}}(i\omega_n, \mathbf{k})$
  */
-g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_wk_cvt sigma_wk);
+g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_wk_cvt sigma_wk, mpi::communicator const &c = {});
 
 /** Construct an interacting Matsubara frequency local (:math:`\mathbf{r}=\mathbf{0}`) lattice Green's function :math:`G_{a\bar{b}}(i\omega_n)`
    
@@ -101,7 +101,7 @@ g_wk_t lattice_dyson_g_wk(double mu, e_k_cvt e_k, g_wk_cvt sigma_wk);
  @param sigma_w imaginary frequency self-energy :math:`\Sigma_{\bar{a}b}(i\omega_n)`
  @return Matsubara frequency lattice Green's function $G_{a\bar{b}}(i\omega_n, \mathbf{k})$
  */
-g_w_t lattice_dyson_g_w(double mu, e_k_cvt e_k, g_w_cvt sigma_w);
+g_w_t lattice_dyson_g_w(double mu, e_k_cvt e_k, g_w_cvt sigma_w, mpi::communicator const &c = {});
 
 /** Inverse fast fourier transform of imaginary frequency Green's function from k-space to real space
 
@@ -110,7 +110,7 @@ g_w_t lattice_dyson_g_w(double mu, e_k_cvt e_k, g_w_cvt sigma_w);
     @param g_wk k-space imaginary frequency Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{k})`
     @return real-space imaginary frequency Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{r})`
  */
-g_wr_t fourier_wk_to_wr(g_wk_cvt g_wk);
+g_wr_t fourier_wk_to_wr(g_wk_cvt g_wk, mpi::communicator const &c = {});
   
 /** Fast fourier transform of imaginary frequency Green's function from real-space to k-space
 
@@ -119,7 +119,7 @@ g_wr_t fourier_wk_to_wr(g_wk_cvt g_wk);
     @param g_wr real-space imaginary frequency Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{r})`
     @return k-space imaginary frequency Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{k})`
  */
-g_wk_t fourier_wr_to_wk(g_wr_cvt g_wr);
+g_wk_t fourier_wr_to_wk(g_wr_cvt g_wr, mpi::communicator const &c = {});
 
 /** Fast fourier transform of real-space Green's function from Matsubara frequency to imaginary time
 
@@ -128,7 +128,7 @@ g_wk_t fourier_wr_to_wk(g_wr_cvt g_wr);
     @param g_wr real-space imaginary frequency Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{r})`
     @return real-space imaginary time Green's function :math:`G_{a\bar{b}}(\tau, \mathbf{r})`
  */
-g_tr_t fourier_wr_to_tr(g_wr_cvt g_wr, int nt=-1);
+g_tr_t fourier_wr_to_tr(g_wr_cvt g_wr, int nt=-1, mpi::communicator const &c = {});
 
 /** Fast fourier transform of real-space Green's function from imaginary time to Matsubara frequency
 
@@ -137,6 +137,6 @@ g_tr_t fourier_wr_to_tr(g_wr_cvt g_wr, int nt=-1);
     @param g_tr real-space imaginary time Green's function :math:`G_{a\bar{b}}(\tau, \mathbf{r})`
     @return real-space Matsubara frequency Green's function :math:`G_{a\bar{b}}(i\omega_n, \mathbf{r})`
  */
-g_wr_t fourier_tr_to_wr(g_tr_cvt g_tr, int nw=-1);
+g_wr_t fourier_tr_to_wr(g_tr_cvt g_tr, int nw=-1, mpi::communicator const &c = {});
   
 } // namespace triqs_tprf
diff --git a/c++/triqs_tprf/mpi.hpp b/c++/triqs_tprf/mpi.hpp
index 0b11b42f..2b6e4fbf 100644
--- a/c++/triqs_tprf/mpi.hpp
+++ b/c++/triqs_tprf/mpi.hpp
@@ -29,7 +29,7 @@
 namespace triqs_tprf {
 
 template<class T>
-auto mpi_view(const array<T, 1> &arr, mpi::communicator const & c) {
+auto mpi_view(const array<T, 1> &arr, mpi::communicator const &c = {}) {
 
   auto slice = itertools::chunk_range(0, arr.shape()[0], c.size(), c.rank());
 
@@ -42,13 +42,7 @@ auto mpi_view(const array<T, 1> &arr, mpi::communicator const & c) {
 }
 
 template<class T>
-auto mpi_view(const array<T, 1> &arr) {
-  mpi::communicator c;
-  return mpi_view(arr, c);
-}
-  
-template<class T>
-auto mpi_view(const T &mesh, mpi::communicator const & c) {
+auto mpi_view(const T &mesh, mpi::communicator const &c = {}) {
 
   auto slice = itertools::chunk_range(0, mesh.size(), c.size(), c.rank());
   int size = slice.second - slice.first;
@@ -78,11 +72,5 @@ auto mpi_view(const T &mesh, mpi::communicator const & c) {
 
   return arr;
 }
-
-template<class T>
-auto mpi_view(const T &mesh) {
-  mpi::communicator c;
-  return mpi_view(mesh, c);
-}
   
 } // namespace triqs_tprf