2.5 Libraries

2.5.1 BLAS and LAPACK

QUANTUM ESPRESSO needs the BLAS and LAPACK mathematical libraries. As a rule, one should always use vendor-specific optimized BLAS and LAPACK, such as e.g. those found in Intel's MKL. They often yield huge performance gains with respect to compiled libraries. configure always try to locate the best mathematical libraries.

If optimized BLAS and LAPACK are not available, QUANTUM ESPRESSO automatically downloads and compiles them. Another option is to try the ATLAS library: http://math-atlas.sourceforge.net/. Note that ATLAS is not a complete replacement for LAPACK: it contains all of the BLAS, plus the LU code, plus the full storage Cholesky code. Follow the instructions in the ATLAS distributions to produce a full LAPACK replacement. Also note that the ATLAS project appears to be dead.

Sergei Lisenkov reported success and good performances with optimized BLAS by Kazushige Goto. The library is now available under an open-source license: see the GotoBLAS2 page at
http://www.openmathlib.org/OpenBLAS/.

2.5.2 FFT

The FFTXlib package of QUANTUM ESPRESSO contains a copy of an old FFTW library, but also supports the newer FFTW3 library and some vendor-specific FFT libraries. It is strongly recommanded to use FFT's from an optimized library, such as e.g. those contained in Intel MKL. configure will first search for vendor-specific FFT libraries; if none is found, it will search for an external FFTW v.3 library; if none is found, it will fall back to the internal copy of FFTW. configure will add the appropriate preprocessing options:

• -D__DFTI for DFTI (Intel MKL library),
• -D__FFTW3 for FFTW3 (external),
• -D__FFTW for FFTW (internal library),
• -D__LINUX_ESSL for ESSL on IBM Linux machines (obsolete?),
• -DASL for NEC ASL library on NEC machines (obsolete?),

to DFLAGS in the make.inc file. If you edit make.inc manually, please note that one and only one among the mentioned preprocessing option must be set.

If you have MKL libraries, you may either link FFTW3 from MKL, or use DFTI (recommended).

2.5.3 MPI libraries

MPI libraries are needed for parallel execution, unless you are happy with OpenMP-only multicore parallelization. In well-configured machines, configure should find the appropriate parallel compiler for you, and this should find the appropriate libraries. If this does not happen, see Sec.2.9.3.

2.5.4 HDF5

The HDF5 library (https://www.hdfgroup.org/downloads/hdf5/), v.1.8.16 or later, can be used to perform binary I/O using the HDF5 format.

If compiling the HDF5 library from sources, attention must be paid to pass options:
–enable-fortran, –enable-fortran2003, and –enable-parallel (see below), to the configure script of HDF5 (not of QUANTUM ESPRESSO).

To use HDF5 is usually sufficient to specify the path to the fortran compiler wrapper for HDF5 (h5fc of h5pfc with the –with-hdf5= option of configure. If the wrapper is in the default path, just use –with-hdf5=yes. The configure script is usually able to extract the linker options and the include directory path from the output of the wrapper. If it fails, the user can provide configure options –with-hdf5-libs=<options> and –with-hdf5-include=<path> for the linker options and include path respectively. These options are often needed when using the HDF5 packages provided by many LINUX distributions. In this case you may first try the –with-hdf5=yes option. If it fails, just type command h5fc –show (or h5pfc if you are using parallel HDF5): the command will print out the linker and include options to be passed manually to the configure script.

The configure script is able to determine whether one is linking to a serial or parallel HDF5 library, and will set the flag -D__HDF5_SERIAL in the make.inc file accordingly.

2.5.5 Other libraries

The accelerated version of the code for NVidia GPU's uses standard CUDA libraries cublas, cufft, curand, cusolver that are available from the NVidia HPC SDK and found by configure.

If the appropriate configure option is set, the code downloads and compile the FoX library (m4 is required in this case) for reading and writing xml files. This option is useful only for debugging.

QUANTUM ESPRESSO can use the MASS vector math library from IBM, but for a single routine and only with the XLF compiler, so it is hardly worth it.

2.5.6 In case of trouble

The configure script attempts to find optimized libraries, but may fail if they have been installed in non-standard places. You should examine the final value of BLAS_LIBS, LAPACK_LIBS, FFT_LIBS, MPI_LIBS (if needed), either in the output of configure or in the generated make.inc, to check whether it found all the libraries that you intend to use.

If some library was not found, you can specify a list of directories to search in the environment variable LIBDIRS, and rerun configure; directories in the list must be separated by spaces. For example:

   ./configure LIBDIRS="/opt/intel/oneapi/mkl /usr/lib/math"

If this still fails, you may set some or all of the *_LIBS variables manually and retry. For example:

   ./configure BLAS_LIBS="-L/usr/lib/math -lf77blas -latlas_sse"

Beware that in this case, configure will blindly accept the specified value, and won't do any check or extra search.