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dft_tools/test/triqs/arrays/mat_vec_mul.output
Olivier Parcollet b534936589 Fix matrix * alias issue and adapt det_manip
- The previous version of the * operator for matrix was too clever.
It was giving a lazy object and then rewriting C = A *B into gemm (a,A,B,0,C).
The pb was in case of aliasing : when e.g. C = A, or is a part of A.
gemm is not correct that case, and as a result generic code like
a = a *b
may not be correct in matrix case, which is unacceptable.

- So we revert to a simple * operator for matrix
that does immediate computation.
Same thing for matrix* vector

- we also suppress a_x_ty class.

-> for M = a * b,
when M is a matrix, there is no overhead due to move assignment
-> however, when M is a view, there is an additionnal copy.

-Correctness comes first, hence the fix.
However, if one wants more speed and one can guarantee that
there is no aliasing possible, then one has to write a direct gemm call.

-> det_manip class was adapted, since in that case, we can show there
no alias, and we want the speed gain, so the * ops where replaced
by direct blas call (using the array blas interface).

-> also gemm, gemv, ger were overloaded in the case the return
matrix/vector (i.e. last parameter of the function) is not an lvalue,
but a temporary view created on the fly.
2013-09-11 18:49:22 +02:00

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A =
[[1,3,5,7,9]
[2,4,6,8,10]
[3,5,7,9,11]
[4,6,8,10,12]
[5,7,9,11,13]]
A(R,R) =
[[4,6]
[5,7]]
MC(R) = [1,1]
MB = [10,12] = [0,10,12,0,0]
testing infix
A =
[[4,6]
[5,7]]
MC = [1,1,1,1,1]
MB(R) += A(R,R) * MC(R) = [0,20,24,0,0]
explicit blas call
MC = [1,1,1,1,1]
A =
[[4,6]
[5,7]]
MB = [0,10,12,0,0]
A =
[[4,6]
[5,7]]
MB = [0,10,12,0,0]
A =
[[4,5]
[6,7]]
MB = [0,9,13,0,0]