ops: epetra: revise matrix-matrix product

[mzuzek]

@fnrizzi

refs #451

Contents

• [x] review overload constraints
• [x] add explicit alpha/beta casts
• [x] add missing unit tests for existing overloads
• [x] list overloads and test cases

Overloads

Epetra level-3 pressio::ops::product() (i.e. performing C = alpha * op(A) * op(B) + beta * C) overloads:

A	B	C	op(A)	op(B)
epetra MV	epetra MV	eigen matrix	transpose	nontranspose
epetra MV	epetra MV	dynamic eigen matrix (returned value)	transpose	nontranspose
epetra MV	⨯ (self product)	eigen matrix	transpose	nontranspose
epetra MV	⨯ (self product)	dynamic eigen matrix (returned value)	transpose	nontranspose

Test coverage

Test cases for Epetra level-3 implementations of pressio::ops::product() (op(A) is always transpose and op(B) is always nontranspose):

test	A	B	C
mv_T_mv_storein_eigen_C mv_T_mv_storein_eigen_C_beta0	Epetra_MultiVector	Epetra_MultiVector	Eigen::MatrixXd
mv_T_self_storein_eigen_C mv_T_self_storein_eigen_C_beta0	Epetra_MultiVector	⨯	Eigen::MatrixXd

[mzuzek]

thanks @fnrizzi for your review!