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The basic and most common usage is to run the command sfocu <file1> <file2>. The option -t <dist> allows a distance tolerance in comparing bounding boxes of blocks in two different files to determine which are the same (which have data to compare to one another). You might need to widen your terminal to view the output, since it can be over 80 columns. Sample output follows:
A: 2006-04-25/sod_2d_45deg_4lev_ncmpi_chk_0001
B: 2005-12-14/sod_2d_45deg_4lev_ncmpi_chk_0001
Min Error: inf(2|a-b| / max(|a+b|, 1e-99) )
Max Error: sup(2|a-b| / max(|a+b|, 1e-99) )
Abs Error: sup|a-b|
Mag Error: sup|a-b| / max(sup|a|, sup|b|, 1e-99)
Block shapes for both files are: [8,8,1]
Mag-error tolerance: 1e-12
Total leaf blocks compared: 541 (all other blocks are ignored)
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
Var | Bad Blocks | Min Error || Max Error || Abs Error |
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
| | || Error | A | B || Error | A | B |
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
dens | 502 | 0 || 1.098e-11 | 0.424 | 0.424 || 4.661e-12 | 0.424 | 0.424 |
eint | 502 | 0 || 1.1e-11 | 1.78 | 1.78 || 1.956e-11 | 1.78 | 1.78 |
ener | 502 | 0 || 8.847e-12 | 2.21 | 2.21 || 1.956e-11 | 2.21 | 2.21 |
gamc | 0 | 0 || 0 | 0 | 0 || 0 | 0 | 0 |
game | 0 | 0 || 0 | 0 | 0 || 0 | 0 | 0 |
pres | 502 | 0 || 1.838e-14 | 0.302 | 0.302 || 1.221e-14 | 0.982 | 0.982 |
temp | 502 | 0 || 1.1e-11 | 8.56e-09 | 8.56e-09 || 9.41e-20 | 8.56e-09 | 8.56e-09 |
velx | 516 | 0 || 5.985 | 5.62e-17 | -1.13e-16 || 2.887e-14 | 0.657 | 0.657 |
vely | 516 | 0 || 2 | 1e-89 | -4.27e-73 || 1.814e-14 | 0.102 | 0.102 |
velz | 0 | 0 || 0 | 0 | 0 || 0 | 0 | 0 |
mfrc | 0 | 0 || 0 | 0 | 0 || 0 | 0 | 0 |
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
Var | Bad Blocks | Mag Error || A || B |
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
| | || Sum | Max | Min || Sum | Max | Min |
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
dens | 502 | 4.661e-12 || 1.36e+04 | 1 | 0.125 || 1.36e+04 | 1 | 0.125 |
eint | 502 | 6.678e-12 || 7.3e+04 | 2.93 | 1.61 || 7.3e+04 | 2.93 | 1.61 |
ener | 502 | 5.858e-12 || 8.43e+04 | 3.34 | 2 || 8.43e+04 | 3.34 | 2 |
gamc | 0 | 0 || 4.85e+04 | 1.4 | 1.4 || 4.85e+04 | 1.4 | 1.4 |
game | 0 | 0 || 4.85e+04 | 1.4 | 1.4 || 4.85e+04 | 1.4 | 1.4 |
pres | 502 | 1.221e-14 || 1.13e+04 | 1 | 0.1 || 1.13e+04 | 1 | 0.1 |
temp | 502 | 6.678e-12 || 0.000351 | 1.41e-08 | 7.75e-09 || 0.000351 | 1.41e-08 | 7.75e-09 |
velx | 516 | 3.45e-14 || 1.79e+04 | 0.837 | -6.09e-06 || 1.79e+04 | 0.837 | -6.09e-06 |
vely | 516 | 2.166e-14 || 1.79e+04 | 0.838 | -1.96e-06 || 1.79e+04 | 0.838 | -1.96e-06 |
velz | 0 | 0 || 0 | 0 | 0 || 0 | 0 | 0 |
mfrc | 0 | 0 || 3.46e+04 | 1 | 1 || 3.46e+04 | 1 | 1 |
-----+------------+-----------++-----------+-----------+-----------++-----------+-----------+-----------+
FAILURE
“Bad Blocks” is the number of leaf blocks where the data was found to differ between datasets. Four different error measures (min/max/abs/mag) are defined in the output above. In addition, the last six columns report the sum, maximum and minimum of the variables in the two files. Note that the sum is physically meaningless, since it is not volume-weighted. Finally, the last line permits other programs to parse the sfocu output easily: when the files are identical, the line will instead read SUCCESS.
It is possible for sfocu to miss machine-precision variations in the data on certain machines because of compiler or library issues, although this has only been observed on one platform, where the compiler produced code that ignored IEEE rules until the right flag was found.