Belos: Provide `Tpetra` version of LSQR examples

[tlamonthezie]

Hello @stmcgovern

The new PrecLSQRTpetraExFile example would require to add ifpack2 as dependency for Belos but it would add a circular dependency. It is due to the fact that in Ifpack2 depnds on Belos (only for some tests and examples as I can see)

I think there are 2 possibilities if we want to have a new Tpetra version of this example:

• Option A: Add PrecLSQRTpetraExFile to Ifpack2 examples
• Option B: Add PrecLSQRTpetraExFile to Belos examples + move Belos/Ifpack2 tests and examples from Ifpack2 to Belos package + change dependencies (make belos depend on Ifpack2 instead of the inverse, like it is the case with Ifpack)

I think the option A is easier to apply but the option B might be more logic even if we have to modify 2 packages at once. @stmcgovern could you please give me some guidance on that or ask Belos and Ifpack2 package owners ? Or is there maybe a place where to add tests and examples external to thse 2 packages to prevent the circular dependency ?

As I am writing this comment I am working on making the example working by ignoring the dependency problem but we will have to know how to make it work at build stage to not have dependency issue.

[stmcgovern]

Hello @stmcgovern

The new PrecLSQRTpetraExFile example would require to add ifpack2 as dependency for Belos but it would add a circular dependency. It is due to the fact that in Ifpack2 depnds on Belos (only for some tests and examples as I can see)

I think there are 2 possibilities if we want to have a new Tpetra version of this example:

* Option A: Add `PrecLSQRTpetraExFile` to `Ifpack2` examples

* Option B: Add `PrecLSQRTpetraExFile` to `Belos` examples + move Belos/Ifpack2 tests and examples from `Ifpack2` to `Belos` package + change dependencies (make belos depend on Ifpack2 instead of the inverse, like it is the case with Ifpack)

I think the option A is easier to apply but the option B might be more logic even if we have to modify 2 packages at once. @stmcgovern could you please give me some guidance on that or ask Belos and Ifpack2 package owners ? Or is there maybe a place where to add tests and examples external to thse 2 packages to prevent the circular dependency ?

As I am writing this comment I am working on making the example working by ignoring the dependency problem but we will have to know how to make it work at build stage to not have dependency issue.

@hkthorn and @jennloe do you have any suggestions about the strategies @tlamonthezie has proposed?