Gfilui

I used the command

 ./configure --prefix=/usr/local/ --enable-gnu --enable-fftw --with-fftw=/home/kiran1209/Downloads/fftw-3.3.4/.libs/ LDflags="-lmpi_f90 -lmpi_f77"

( Is the command correct?)

but after running for some time it gives the error

configure: error: libfftw3.a was not found in given location!

The file exists but with different extension .la. What should I do about this error?

The first thing to note is that the argument to --with-fftw must be the top level path to the FFTW3 header files and libraries. So for example if the headers are in /usr/include and the libraries are under /usr/lib (the default, when package libfftw3-dev is installed from the Ubuntu repository), the value should be given as --with-fftw=/usr

The additional issue in this case is that the provided configure script appears to be hard-wired to look in only the lib and lib64 subdirectories:

 3315 if test -e $withfftw/lib/libfftw3.a ; then
 3316 FFTW_INC="-I$withfftw/include"
 3317 
 3318 FFTW_LIB="$withfftw/lib/libfftw3.a"
 3319 
 3320 elif test -e $withfftw/lib64/libfftw3.a ; then
 3321 FFTW_INC="-I$withfftw/include"
 3322 
 3323 FFTW_LIB="$withfftw/lib64/libfftw3.a"
 3324 
 3325 else
 3326 as_fn_error $? "libfftw3.a was not found in given location!" "$LINENO" 5
 3327 fi

The use of a lib64 subdirectory is an old convention that pre-dates Debian's Multiarch framework - the modern location for 64-bit libraries would be lib/x86_64-linux-gnu

There may be a 'clean' way to re-configure that (perhaps using autoreconf) however I don't know it - if you don't mind using a quick'n'dirty fix, then it should be sufficient to fix the search location using sed:

sed -i.bak 's:lib64:lib/x86_64-linux-gnu:g' configure

and then re-run ./configure

Ref. @steeeldriver: sed -i.bak 's:lib64:lib/x86_64-linux-gnu:g'
configure

The sed editing is OK with the first configuring. But make generates a new file configure.

Ubuntu 16.04 and 18.04 build example:

cd /usr/lib/
sudo ln -s x86_64-linux-gnu/libfftw3.a

cd /usr/bin/
sudo ln -s aclocal-1.15 aclocal-1.14
sudo ln -s automake-1.15 automake-1.14

git clone https://github.com/sdsc/p3dfft.git
cd p3dfft/
./configure --enable-fftw --with-fftw=/usr && make

No errors, 16.04 or 18.04 .

EDIT : Using your new options, ref. make: *** [all] Error 2 while installing P3DFFT

./configure --enable-gnu --enable-fftw --with-fftw=/usr --enable-estimate --enable-measure --enable-patient

... and using the default fftw3 : No errors. Neither with p3dfft-2.7.6 or git clone https://github.com/sdsc/p3dfft.git

Using fftw3 in /usr/local/: fftw3_3.3.7.orig.tar.xz http://archive.ubuntu.com/ubuntu/pool/main/f/fftw3/fftw3_3.3.7.orig.tar.xz

cd fftw-3.3.7/
./configure --enable-shared --enable-static --enable-threads --enable-openmp --enable-mpi --prefix=/usr/local
make && sudo make install

And p3dfft/:

./configure --enable-gnu --enable-fftw --with-fftw=/usr/local --enable-estimate --enable-measure --enable-patient
make 

No errors, 16.04 or 18.04, except for cannot find -lmpichf90 : libmpichf90.a, libmpichf90.so i.e. if the driver test is run.
No libmpichf90.a, libmpichf90.so in the default Ubuntu packages.