Accuracy
########

EPW accuracy on various quantities
==================================

Some physical quantities are more sensitive to numerical instabilities than other. Below is a list of quantities tested by the EPW Test Farm and their related 
accuracies. 

Note that this is an upper bounds and show the maximum variation on a quantity due to different compiler, hardware, libraries, level of optimization and parallelism.  

=================================  ==============  =====================  ======================  ===========================  ======
Physical quantity                  Absolute error  Relative error [in %]  Benchmark value         Slave                        Note
=================================  ==============  =====================  ======================  ===========================  ======
DOS                                0.00001         0.001                  stable           
Eigenenergy (eV)                   0.001           0.5                    -0.0219 (epw_soc)       EPW-farmer_gcc485            stable
Re[Sigma] (meV)                    0.02            2.0                    -982.600493 (epw_soc)   EPW-farmer_gcc485            stable
Im[Sigma] (meV)                    0.04            0.04                   1858.014377 (epw_soc)   EPW-farmer_gcc485            stable
Z                                  0.08            0.08                   -11.665563 (epw_soc)    EPW-farmer_gcc485            stable
PH lamda (lambda)                  0.00001         0.001                  stable
PH lamda (lambda_tr)               0.00001         0.01                   stable
El lamda (lam)                     0.00001         3.0                    -0.00015 (epw_base)     EPW-farm2_pgi15              stable
Integrated lamda                   0.0001          0.02                   0.6690848 (epw_soc)     EPW-farm2_pgi15              stable
Integrated lamda TR                3               100.0                  2.7783115 (epw_soc)     EPW-farm2_intel13            bug
Ph gamma (meV)                     0.008           900                    -0.001178 (epw_soc)     EPW-farm2_intel13            stable
Ph freq (meV)                      0.005           0.05                   104.4255 (epw_trev)     desktop                      stable
logavg for Tc                      0.00001         0.2                    0.005807  (epw_trev)    EPW-farmer4_gcc485_openblas  stable
l_a2F for Tc                       0.001           0.2                    0.0838588 (epw_trev)    EPW-farm2_intel13            stable
Fermi level (eV)                   0.00001         0.001                  stable
lambda_max                         0.0005          0.01                   5.164161 (epw_super)    desktop                      stable
lambda_k_max                       0.0001          0.01                   1.510491 (epw_super)    desktop                      stable
Electron-phonon coupling strength  0.0005          0.05                   0.939445 (epw_super)    desktop                      stable
Allen-Dynes Tc (K)                 0.02            0.05                   31.8408371 (epw_super)  EPW-farm2_intel13            stable
BCS superconducting gap            0.0001          0.05                   0.0048291 (epw_super)   EPW-farm2_intel13            stable
=================================  ==============  =====================  ======================  ===========================  ======

The Benchmark value is the value from the tests that lead to the largest error. In parenthesis is the name of the test from the test suite.

If you want to run the test yourself, you can do so by going to

``cd espresso/test-suite/``

Then type 

``make prolog``

to generate the userconfig file. 

You can then run an epw test in sequential by doing 

``make run-custom-test testdir=epw_base``

and in parallel by doing

``make run-custom-test-parallel testdir=epw_base``