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2.2 Prerequisites

To install QUANTUM ESPRESSO from source, you need first of all a minimal Unix environment, that is: a command shell (e.g., bash, sh) and utilities `make`, `awk`, `sed`. For MS-Windows, see Sec.2.8.4.

Note that the scripts contained in the distribution assume that the local language is set to the standard, i.e. "C"; other settings may break them. Use `export LC_ALL=C` (sh/bash) or `setenv LC_ALL C` (csh/tcsh) to prevent any problem when running scripts (including installation scripts).

Second, you need C and Fortran compilers, compliant with C89 and F2003 standards1. For parallel execution, you will also need MPI libraries and a parallel (i.e. MPI-aware) compiler. For massively parallel machines, or for simple multicore parallelization, an OpenMP-aware compiler and libraries are also required. For GPU's, you will need the CUDA Fortran version and to compile with the PGI compiler and run with CUDA run-time environment.

As a rule, QUANTUM ESPRESSO tries to keep compatibility with older compilers, avoiding nonstandard extensions and newer features that are not widespread or stabilized. If however your compiler is very old (say older than ∼5 years or so) it is quite likely that something will not work. The same applies to mathematical and MPI libraries.

Big machines with specialized hardware (e.g. IBM SP, CRAY, etc) typically have a Fortran compiler with MPI and OpenMP libraries bundled with the software. Workstations or ``commodity'' machines, using PC hardware, may or may not have the needed software. If not, you need either to buy a commercial product (e.g Intel, NAG, PGI) or to use an open-source compiler like gfortran from the gcc distribution. Some commercial compilers (e.g. PGI) may be available free of charge under some conditions (e.g. academic or personal usage).

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