qmcpack/tests/solids/NiO_a4_e48_pp

===============
L2 test details
===============
The tests include short and long VMC runs for a 4 atom cell of NiO 
with an L2 pseudopotential used for Ni.

Reference data was generated with runs the same overall length 
(blocks x steps) as those included in ./qmc-ref, but using 10x more blocks 
and 10x fewer steps.  Using more blocks reduced the statistical error of 
the error bars, but resulted in output data files that were too large 
to include in the QMCPACK distribution.  The reference values and error 
bars were therefore computed from the higher block count runs.  The 
included reference runs were confirmed to be consistent with the original 
higher block count runs.  

Version of the code used to create the reference data:

  Git commit 168a57c0e522c5ef9e0e7d96293442688198e24a 

Reference data from the high block count VMC runs is found below:

             LocalEnergy               Variance                 ratio 
NiO-L2-ref  -371.119855 +/- 0.001945   16.541242 +/- 0.202857   0.0446

For comparison, corresponding data for the lower block count VMC 
reference data found in ./qmc-ref is:

>qmca -e 2 -q ev qmc-ref/NiO-L2-ref*scalar*
             LocalEnergy               Variance                 ratio 
NiO-L2-ref  -371.118862 +/- 0.001859   16.427735 +/- 0.104492   0.0443

>qmca -e 2 -q ts qmc-ref/NiO-L2-ref*scalar*
NiO-L2-ref   TotalSamples          =  12774400.000000 +/- 0.000000

Test input files were created by reducing the number of steps from the 
included reference by a factor of 10 for the "long" tests and by a 
further factor of 10 for the "short" tests.

Reference values for the mean local energy and variance were taken 
from the high block count reference runs.  Expected error bars were 
derived from the high block count data by multiplying the reference 
error bars by a factor of sqrt(10+1) and sqrt(100+1) for the long 
and short tests, respectively.  The factor of +1 accounts for the 
error bar intrinsic to the high block count runs.

The target means and error bars for long and short tests are:

                 refmean     referr    longerr   shorterr
NiO-L2 energy   -371.119855  0.001945  0.006451  0.019547

The number of samples expected from the long and short runs are 
(with all blocks included):

                TotalSamples
NiO-L2-long     1280000
NiO-L2-short    128000

Error bars from typical long and short runs are shown below:

Typical long run results:

              Energy                   Variance                ratio
NiO-L2-long  -371.126423 +/- 0.006136  16.003283 +/- 0.148233  0.0431

Typical short run results:

              Energy                   Variance                ratio
NiO-L2-short -371.123245 +/- 0.018611  15.383094 +/- 0.190840  0.0415

Rough timings for the tests on a circa 2018 Intel Skylake system are:

>grep 'Total Exe' *long*/*.out
long_test/qmc.out:   Total Execution time = 1.6918e+02 secs

>grep 'Total Exe' *short*/*.out
short_test/qmc.out:  Total Execution time = 1.7596e+01 secs