<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><br class=""></div> I have made a branch <span style="font-family: Menlo; font-size: 14px;" class="">barry/2021-11-25/feature-fftw-seq </span> <a href="https://gitlab.com/petsc/petsc/-/merge_requests/4604" class="">https://gitlab.com/petsc/petsc/-/merge_requests/4604</a> that provides support for using FFTW without MPI, please let us know if you have difficulties with it.<br class=""><div class=""><br class=""></div><div class=""> Barry</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Nov 25, 2021, at 5:15 AM, Fabio Rossi via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov" class="">petsc-users@mcs.anl.gov</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">I am trying to compile petsc with the following options (Gentoo build system):<br class=""><br class="">./configure --prefix=/usr --build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu --mandir=/usr/share/man --infodir=/usr/share/info --datadir=/usr/share --sysconfdir=/etc --localstatedir=/var/lib --libdir=/usr/lib64/petsc/lib64 scrollOutput=1 FFLAGS=-O2 -pipe -fPIC CFLAGS=-march=core2 -O2 -pipe -fPIC CXXFLAGS=-march=core2 -O2 -pipe -fPIC LDFLAGS=-Wl,-O1 -Wl,--as-needed --prefix=/usr/lib64/petsc --with-shared-libraries --with-single-library --with-clanguage=c --with-petsc-arch=linux-gnu-c-opt --with-precision=double --with-gnu-compilers --with-blas-lapack-lib=-lblas -llapack --with-debugging=0 --with-mpi=0 --with-cc=x86_64-pc-linux-gnu-gcc --with-cxx=x86_64-pc-linux-gnu-g++ --with-fortran=1 --with-fc=x86_64-pc-linux-gnu-gfortran --with-mpi-compilers=0 --with-scalar-type=real --with-windows-graphics=0 --with-matlab=0 --with-cmake:BOOL=1 --with-pthread=1 --with-afterimage=0 --without-hdf5 --with-hypre=0 --without-suitesparse --with-superlu=0 --with-x --with-x11 --with-ptscotch=0<br class=""> --with-<br class=""> scalapack=0 --without-mumps --with-imagemagick=0 --with-python=0 --with-boost --with-fftw<br class=""><br class="">so MPI support is disabled, and I get the following configure error:<br class=""><br class="">TESTING: consistencyChecks from config.packages.fftw(/var/tmp/portage/sci-mathematics/petsc-3.15.0/work/petsc-3.15.0/config/BuildSystem/config/package.py:963)<br class="">TESTING: checkDependencies from config.packages.fftw(/var/tmp/portage/sci-mathematics/petsc-3.15.0/work/petsc-3.15.0/config/BuildSystem/config/package.py:872)<br class="">*******************************************************************************<br class=""> UNABLE to CONFIGURE with GIVEN OPTIONS (see configure.log for details):<br class="">-------------------------------------------------------------------------------<br class="">Did not find package MPI needed by fftw.<br class="">Enable the package using --with-mpi<br class=""><br class="">Isn't MPI optional? Where is the error coming from?<br class=""><br class="">If I disable fftw then it compiles successfully.<br class=""><br class="">Fabio<br class=""></div></div></blockquote></div><br class=""></div></body></html>