[AMPL 24497] Load parameter into C++

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1

Hello,

I have a parameter in ampl of the form

param Test[SetA];
and I would like to save the values of this parameter into a vector in C++.
Is it possible to do it?

Thanks

Sam

2

Hi Sam,

Yes, you can retrieve the values and place them into a vector as follows:

ampl::AMPL ampl;
ampl.eval(“set SetA := 1…10; param Test{i in SetA} := 2*i;”);
ampl::DataFrame df = ampl.getParameter(“Test”).getValues();
std::vector values;
for (ampl::VariantRef : df.getColumn(“Test”)) {
values.push_back(v.dbl());
}

ampl.getParameter(“Test”).getValues() returns a ampl::DataFrame with the data for that parameter.
df.getColumn(“Test”) returns the column Test from the ampl::DataFrame.
You can then iterate over this column and place each value into the vector.

3

Thank you Filipe!!
That’s very helpful!!:relaxed:

4

Hello,

is it possible that there is mistake?? I tried it on my code but it returns two errors:

  1. expected unqualified-id before ‘:’ token …the one in the for loop
  2. ‘v’ was not declared in this scope …in the for loop

Thanks
Sam

5

Hi Sam,

Somehow “v” disappeared when copying the example here. In the for loop it should be: “ampl::VariantRef v” as follows:

for (ampl::VariantRef v: df.getColumn(“Test”))

6

Ok thanks…problem solved!:relaxed: