diff --git a/base/modules/tools/psb_cd_tools_mod.f90 b/base/modules/tools/psb_cd_tools_mod.f90
index 3445e950..531072ca 100644
--- a/base/modules/tools/psb_cd_tools_mod.f90
+++ b/base/modules/tools/psb_cd_tools_mod.f90
@@ -79,6 +79,18 @@ module psb_cd_tools_mod
     end subroutine psb_cdcpy
   end interface
 
+  interface psb_cd_renum_block
+    subroutine psb_cd_renum_block(desc_in, desc_out, info)
+      import :: psb_ipk_, psb_desc_type
+
+      implicit none
+      !....parameters...
+
+      type(psb_desc_type), intent(inout) :: desc_in
+      type(psb_desc_type), intent(out)   :: desc_out
+      integer(psb_ipk_), intent(out)     :: info
+    end subroutine psb_cd_renum_block
+  end interface
 
   interface psb_cdprt
     subroutine psb_cdprt(iout,desc_p,glob,short,verbosity)
diff --git a/base/tools/Makefile b/base/tools/Makefile
index 029644c4..962a7faa 100644
--- a/base/tools/Makefile
+++ b/base/tools/Makefile
@@ -2,7 +2,7 @@ include ../../Make.inc
 
 FOBJS = psb_cdall.o psb_cdals.o psb_cdalv.o psb_cd_inloc.o psb_cdins.o psb_cdprt.o \
 	psb_cdren.o psb_cdrep.o psb_get_overlap.o psb_cd_lstext.o\
-	psb_cdcpy.o psb_cd_reinit.o psb_cd_switch_ovl_indxmap.o \
+	psb_cdcpy.o psb_cd_reinit.o psb_cd_switch_ovl_indxmap.o psb_cd_renum_block.o \
 	psb_dspalloc.o psb_dspasb.o \
 	psb_dspfree.o psb_dspins.o psb_dsprn.o \
 	psb_sspalloc.o psb_sspasb.o \
diff --git a/base/tools/psb_cd_renum_block.F90 b/base/tools/psb_cd_renum_block.F90
new file mode 100644
index 00000000..bd064187
--- /dev/null
+++ b/base/tools/psb_cd_renum_block.F90
@@ -0,0 +1,152 @@
+!   
+!                Parallel Sparse BLAS  version 3.5
+!      (C) Copyright 2006-2018
+!        Salvatore Filippone    
+!        Alfredo Buttari      
+!   
+!    Redistribution and use in source and binary forms, with or without
+!    modification, are permitted provided that the following conditions
+!    are met:
+!      1. Redistributions of source code must retain the above copyright
+!         notice, this list of conditions and the following disclaimer.
+!      2. Redistributions in binary form must reproduce the above copyright
+!         notice, this list of conditions, and the following disclaimer in the
+!         documentation and/or other materials provided with the distribution.
+!      3. The name of the PSBLAS group or the names of its contributors may
+!         not be used to endorse or promote products derived from this
+!         software without specific written permission.
+!   
+!    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+!    ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+!    TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+!    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE PSBLAS GROUP OR ITS CONTRIBUTORS
+!    BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+!    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+!    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+!    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+!    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+!    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+!    POSSIBILITY OF SUCH DAMAGE.
+!   
+!    
+!
+! Subroutine: psb_cd_renum_block
+!   Produces a clone of a descriptor.
+! 
+! Arguments: 
+!    desc_in  - type(psb_desc_type).         The communication descriptor to be cloned.
+!    desc_out - type(psb_desc_type).         The output communication descriptor.
+!    info     - integer.                       Return code.
+subroutine psb_cd_renum_block(desc_in, desc_out, info)
+
+  use psb_base_mod, psb_protect_name => psb_cd_renum_block
+
+  implicit none
+  !....parameters...
+
+  type(psb_desc_type), intent(inout) :: desc_in
+  type(psb_desc_type), intent(out)   :: desc_out
+  integer(psb_ipk_), intent(out)     :: info
+
+  !locals
+  type(psb_gen_block_map), allocatable :: blck_map
+  integer(psb_ipk_), allocatable :: lidx(:),reflidx(:)
+  integer(psb_lpk_), allocatable :: gidx(:),vnl(:)
+  integer(psb_ipk_) :: i,n_row, n_col
+  integer(psb_lpk_) :: li,n_glob_row, n_glob_col
+  integer(psb_ipk_) :: np,me,ictxt, err_act
+  integer(psb_ipk_) :: debug_level, debug_unit
+  character(len=20)   :: name
+  
+  debug_unit  = psb_get_debug_unit()
+  debug_level = psb_get_debug_level()
+
+  if (psb_get_errstatus() /= 0) return 
+  info = psb_success_
+  call psb_erractionsave(err_act)
+  name = 'psb_cd_renum_block'
+
+  ictxt = desc_in%get_context()
+
+  ! check on blacs grid 
+  call psb_info(ictxt, me, np)
+  if (debug_level >= psb_debug_ext_) &
+       & write(debug_unit,*) me,' ',trim(name),': Entered'
+  if (np == -1) then
+    info = psb_err_context_error_
+    call psb_errpush(info,name)
+    goto 9999
+  endif
+
+  call desc_in%clone(desc_out,info)
+  if (desc_in%is_ovl()) then
+    write(0,*) 'Warning: descriptor with overlap, not going to clone into BLOCK'
+  else
+    !
+    ! Ok, convert into a GEN BLOCK. 
+    !
+    allocate(psb_gen_block_map :: blck_map, stat=info) 
+    if (info == 0) allocate(vnl(0:np),stat=info)
+    if (info /= 0) then
+      info = psb_err_alloc_dealloc_
+      call psb_errpush(info,name)
+      goto 9999
+    endif
+    n_row = desc_in%get_local_rows()
+    n_col = desc_in%get_local_cols()
+    n_glob_row = desc_in%get_global_rows()
+    n_glob_col = desc_in%get_global_cols()
+    vnl = 0
+    vnl(me) = n_row
+    call psb_sum(ictxt,vnl)
+    vnl(1:np) = vnl(0:np-1)
+    vnl(0) = 0
+    do i=1,np
+      vnl(i) = vnl(i-1)+vnl(i)
+    end do
+    allocate(lidx(n_col),reflidx(n_col),gidx(n_col),stat=info)
+    if (info /= 0) then
+      info = psb_err_alloc_dealloc_
+      call psb_errpush(info,name)
+      goto 9999
+    endif
+    !
+    ! A GEN_BLOCK distribution would just assign indices 1:N_R0
+    ! to process 0, N_R0+1:N_R0+N_R1 to process 1 and so on;
+    ! once these are set you can get the others by invoking
+    ! HALO on the old descriptor, then put the map into the new
+    ! one. Halo lists are stored in local indices, so they will
+    ! continue to work since local indices stay the same, it's
+    ! only the global indices that were reshuffled.
+    !
+    reflidx(1:n_col) = [(i,i=1,n_col)]
+    gidx(1:n_row)    = reflidx(1:n_row) + vnl(me)
+    call psb_halo(gidx,desc_in,info)
+    if (info == 0) call blck_map%gen_block_map_init(ictxt,n_row,info)
+    if (info == 0) call blck_map%g2l_ins(gidx,lidx,info,lidx=reflidx)
+    if (info == 0) call blck_map%asb(info)
+  
+    if (info /= psb_success_) then
+      info = psb_err_from_subroutine_
+      call psb_errpush(info,name)
+      goto 9999
+    endif
+    call move_alloc(blck_map,desc_out%indxmap)
+  end if
+  
+  if (info /= psb_success_) then
+    info = psb_err_from_subroutine_
+    call psb_errpush(info,name)
+    goto 9999
+  endif
+  if (debug_level >= psb_debug_ext_) &
+       & write(debug_unit,*) me,' ',trim(name),': Done'
+
+  call psb_erractionrestore(err_act)
+  return
+
+9999 call psb_error_handler(ictxt,err_act)
+
+  return
+
+end subroutine psb_cd_renum_block