|[eigen] lazy evaluation in sparse matrix multiply|
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in trying out some of the Eigen sparse-matrix functionality, I noticed,
that unlike dense matrix multiplication, sparse matrices appear to
default to lazy evaluation of matrix multiplication.
This causes an expression of the type
M = M * M;
to yield a zero matrix when used with sparse matrices.
Forced evaluation as in
M = (M * M).eval();
on the other hand, has the desired effect.
I suggest setting the evaluate-before-assigning flag for sparse
P.S.: What is the current status of complex Hermitian sparse (or block
tridiagonal) eigenproblems in Eigen?