The NF does not expand the sum() function

[Francesco Casella]

Please check the ​ScalableTestSuite.Thermal.HeatExchanger.ScaledExperiments.CocurrentHeatExchangerEquations_N_10 model. It fails at link time due to the lack of definition of the sum_metatype_array type.

The NF flattens this equation

QtotA = sum(QA);

while the old FE gives

  QtotA = QA[1] + QA[2] + QA[3] + QA[4] + QA[5] + QA[6] + QA[7] + QA[8] + QA[9];

As i #4863 I'm not sure if we should expand the array when the DAE structure is created, or rather extend the code generation to handle the sum function explicitly.

If expanding the array in the NF is easily accomplished, I would suggest to do that, at least for the time being, so we can get the maximum coverage without waiting for somebody to fix the code generation.