Frequently asked questions

Installation

What is tddft=yes?

Enables real-time TDDFT support via ce-tddft. Real-time TDDFT also supports adding or replacing external potentials during propagation.

tddft=yes python -m pip install ./QEpy

Can I use CMake for QE?

No. Use the traditional ./configure && make workflow for Quantum ESPRESSO.

Running

Error in routine allocate_fft or fft_type_set

Import qepy before mpi4py. Add import qepy as the first line of your script.

Intel MKL errors

export LD_PRELOAD=/opt/intel/oneapi/mkl/latest/lib/libmkl_rt.so

Intel MPI errors

export LD_PRELOAD=/opt/intel/oneapi/mpi/latest/lib/libmpifort.so

Cannot read wavefunctions / job hangs

• QE stores wavefunctions differently depending on wf_collect. When in doubt, read with a single processor.
• For wavefunctions from old QE (<6.4) or eQE, install qepy==6.5.0.

f90wrap errors

Upgrade f90wrap to the latest release:

python -m pip install --upgrade f90wrap

Segmentation fault

QEpy and mpi4py must be built with the same Fortran/MPI compiler. Reinstall mpi4py:

python -m pip install mpi4py --no-cache-dir

BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES

Without mpi4py, QEpy can still run in parallel (launched by MPI), but you cannot control the communicator from Python. Each new job requires restarting the script or Jupyter kernel. With mpi4py, pass comm to Driver or use comm.py2f() in lower-level calls. See tutorials.

Compiler & platform notes

GCC / LTO

If you see lto1: fatal error, disable link-time optimization:

FFLAGS='-fPIC -fno-lto' CFLAGS='-fPIC -fno-lto' ...

Gfortran ≥10 type mismatch

Add -fallow-argument-mismatch to FFLAGS.

BLAS zdotc segfault

Append -ff2c to QE CFLAGS. See the QE wiki.

Intel compiler issues

• MPI matching errors or wrong initial density on multiple nodes: try a newer Intel compiler or GCC.
• __malloc__ attribute errors: Intel 2021.x may need GCC 4.8–9.2 compatibility headers.

OpenMPI mca_patcher_overwrite

Update OpenMPI or patch shared libraries with patchelf (see legacy docs for OpenMPI 2.1.1 workaround).

macOS

• Illegal Instruction: 4: add -mmacosx-version-min=10.14 to FFLAGS.
• clang: error: no input files: set CPP=gcc -E in make.inc.
• Rpath errors: add -headerpad_max_install_names to LDFLAGS.

QE mbd_c_api.F90 with ifx

Disable libmbd C API before building QE:

export LIBMBD_C_API=0

Deprecated features

• Old XML format (-D__OLDXML): deprecated since QE 6.4. Last QEpy version with support: qepy==6.5.0.

Still stuck? Open an issue on GitHub or contact the developers.