How to use another algorithm when the first approach is too slow?

Question

I need to write a program that uses an alternate algorithm when the algorithm first attempted is taking too long. Here is a minimal example.

foo[n_Integer]:=CheckAbort[TimeConstrained[soln=FactorInteger[n],3],{{n,1}}];
foo[140]
(* {{2,2},{5,1},{7,1}} *)

The example above did what I expected. However, in the next example FactorInteger requires more than three seconds. In that case I wanted foo to return {{n,1}} where (n=10^100+3). Instead I get $Aborted.

foo[10^100+3]
(* $Aborted *)

How do I get foo to do what I wanted.

Answer 1

If I understand what you're trying to do, you can just use TimeConstrained on its own:

foo[n_Integer] := TimeConstrained[FactorInteger[n], 3, {{n, 1}}]