Issue with GRID_MIN/GRID_MAX in HISTOGRAM action

[valsson]

By chance, I noticed an issue with GRID_MIN/GRID_MAX in HISTOGRAM action.

It is possible to give a random string as a value to GRID_MIN/GRID_MAX and the code still runs without an error. Instead, it seems to take 0.0 as the grid value.

For example, you can see this in regtest/analysis/rt-histo:

If you use

HISTOGRAM ...
ARG=x
GRID_MIN=0.0
GRID_MAX=blabla
GRID_BIN=ffa
BANDWIDTH=0.1
LABEL=hA1
... HISTOGRAM

Gives

#! FIELDS x hA1 dhA1_x
#! SET normalisation 1.0000
#! SET min_x 0.0
#! SET max_x blabla
#! SET nbins_x 100
#! SET periodic_x false
0.0000 1.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000

I guess it would be better to add a check on either the parsing of GRID_MIN/GRID_MAX that the parameters gives are proper numbers. Or maybe better in the setBounds function in gridtools/HistogramOnGrid.cpp to avoid this problem happening elsewhere.

[valsson]

I note that using

GRID_MIN=-pi
GRID_MAX=pi

Works as expected

[GiovanniBussi]

@gtribello could it be related to the fact that these conversions do not check the returned bool?

[gtribello]

@GiovanniBussi yes I think if you check the returned bool and put in an error then the problem will be fixed.

[GiovanniBussi]

What scares me is the output of this command:

git grep "Tools::convert"

[GiovanniBussi]

In many cases it is used to convert numbers to strings (e.g. for printing) and that's fine. But when it is used for reading an input it could have this problem.

[GiovanniBussi]

I confirm (in regtest/basic/rt21/plumed.dat) that if I change:

m1g: METAD ARG=r1g HEIGHT=0.1 PACE=10000000 SIGMA=1.0  FILE=H1G GRID_MIN=0.0 GRID_MAX=20.0 GRID_BIN=100

to

m1g: METAD ARG=r1g HEIGHT=0.1 PACE=10000000 SIGMA=1.0  FILE=H1G GRID_MIN=bla GRID_MAX=20.0 GRID_BIN=100

The result is not affected. This is actually very annoying... Thanks @valsson for pointing this out!