Add data pointer (C layer only)

[jschueller]

In the C layer it can be useful to be able to reach user data from
the objective function callback, this adds an extra pointer argument
that is re-passed through the objective callback.

[zaikunzhang]

Hi @jschueller Julien, I agree that it will be useful. It sounds like the C version of "user defined args, f(x, *args)", right?

1. Since we implement it, could we also test it to some extent?
2. To implement the Python version of "user defined args, f(x, *args)", you will not need to use the data_ptr in the C interface, right? As far as I see, it can be implemented using a lambda function (if I understand this concept correctly) easily, right?

Thanks

[jschueller]

1. ok lets do that
2. yes, in Python the language is more powerful: its done it using the objective function decorator

[jschueller]

all good

[zaikunzhang]

f = 0.0/0.0;

What about

f = NAN;

where NAN is a macro from math.h.

cmake --build . --target tests --parallel 4

Do we still run the C and Fortran examples? Or they have been renamed to tests? I think we should run them, and examples is a better name.

Thanks.

[jschueller]

1. I read NAN is not alwasy supported, but let me try
2. yes, we run every tests that are not a stress test, this command only build the tests including tests based on examples

[zaikunzhang]

  // check data is ok
  if (data != data_ref)
  {
    printf("invalid data\n");
    *f = NAN;
  }

So we will not be informed by the test if there is a discrepancy between data and data_ref unless we check the message. What about raising an error so that we know if there is a problem?

[jschueller]

we check at the end that the evaluation number is ok

[zaikunzhang]

I read NAN is not alwasy supported, but let me try

If it is not always supported, we should not use it in the production code, but maybe ok for a test ...

[zaikunzhang]

we check at the end that the evaluation number is ok

It is here, return (fabs(x[0]-3)>2e-2 || fabs(x[1]-2)>2e-2); right? If yes, OK.

[jschueller]

yes