@vv 

Thanks. I'll follow your suggestion.

FunctionPiece.mw

I'm sorry Idid not include any link just uploadaded the file. Thanks

The problem remains. I have uploaded the worksheet containing just a piece of the function that shows the problem. This part has no optimum as you can check in the plot. The complete expression with evalf(int) provides an optimum (when the optimum exists) but the expression with Evalf(int) does not.

Thanks a lot for your help.

First of all thanks vv 963 for your fast and accurate answer.

When I implement your solution, Maple starts to evaluate, it does not produce any error message, which is good, but the problem is that after one hour it keeps on evaluating, without giving the optimum.

The objective function is very "heavy" in the sense that it calls previous procedures which depend on a list of parameters. However in the simple cases, when I can use evalf (int) instead of eval (int), it takes no more than a couple of minutes to get the optimum.

Thanks for your help.