Using AMGX_config_add_parameters with .json options.

Hello,

I am trying to use AMGX_config_add_parameters to modify the solver tolerance (which I need to do in my code to adjust the tolerance to the right-hand side normalization), with an initial configuration based on a .json file.

Using the text syntax such as in the examples, I can use
AMGX_config_add_parameters(&cfg, options);

with the options string containing:

config_version=2, main:convergence=ABSOLUTE, main:tolerance=2.042244e-09

But get a return code 12 (Incorrect amgx configuration provided) when using a .json syntax:

{"config_version": 2, "solver": {"convergence": "ABSOLUTE",  "tolerance": 4.081224e-09}}

Where the "solver" entry in the main .json file (FGMRES.json from the AmgX examples for example) has "scope": "main".

I can't find anything relative to another .json syntax, and would like to avoid the repeated warning that
Cannot read file as JSON object, trying as AMGX config.

Am I missing something ? Could an example of the correct syntax be provided in the documentation ?

Start with the AMGX_config_add_parameters API and the FGMRES.json example mentioned in the issue, then trace how the JSON and text configuration forms are parsed. Document a valid JSON syntax for overriding solver tolerance and convergence without the repeated JSON parsing warning, with an example users can verify against the reported return code.