[SofaPython] print cleaning + SofaPython quaternion dot product

[ErwanDouaille]

This pull request contains few cleaning cout/print/comments.

@ChristianDuriez also added the dot poduct for SofaPython Quaternion

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This PR:

• builds with SUCCESS for all platforms on the CI.
• does not generate new warnings.
• does not generate new unit test failures.
• does not generate new scene test failures.
• does not break API compatibility.
• is more than 1 week old (or has fast-merge label).

Reviewers will merge only if all these checks are true.

[sofabot]

Thank you for your pull request!
Someone will soon check it and start the builds.

[guparan]

[ci-build]

[damienmarchal]

[ci-build]

[hugtalbot]

[ci-build]

[hugtalbot]

[ci-build]

[EulalieCoevoet]

Hi,
I think your "product" function does exactly the same as the "prod" function just below (I checked).
I prefer yours, because of the comment and the fact that the formula is easier to understand/verify.
So maybe we should remove the "prod" function?

[guparan]

Hi,
Python noob here, I see hstack and numpy, I think performance issue. @matthieu-nesme could you help?

[matthieu-nesme]

If it is the same, why adding a new function?
Rather than removing the prod function (that is used in existing code), I would keep it, but replace its code with the new implem (personnaly I would keep the old implementation as a comment as I find it clearer/closer to the math).

But please be sure that is exactly the same.

Also, rather than using directly the [] operator, I would use re(a), im(b)[0], im(b)[1], im(b)[2]. That way it is easier to read, and independent to the scalar order.

[maxime-tournier]

There is a performance issue in both cases:

• hstack + list (!) is useless and can be replaced by res = np.zeros(4); res[:3] = ...; res[-1] = ...;
• yet the proposed version is probably even less efficient since it does all the computations in python which is waaay slower than letting numpy doing its stuff in C

[ChristianDuriez]

Ok... Do we all consider that numpy is mandatory when using SOFA with python ?

It is just a question so that people are aware of that dependency. But I agree to remove the new implementation if less performant .

Erwan will do it

[guparan]

Yes numpy is a mandatory part of SofaPython which is (almost) a mandatory part of SOFA itself.

[damienmarchal]

[ci-build]