Indirect indexing

[Paul Jurczak]

As far as I can tell, indirect indexing like in this Eigen v3.3.90 code snippet:

  Array<int, 1, 9> v{0, 1, 2, 3, 4, 5, 6, 7, 8};
  Array<int, 1, 3> i{6, 3, 0};

  cout << v << endl << v(i) << endl;

which produces:

0 1 2 3 4 5 6 7 8
6 3 0

is not available in Blaze. Is that accurate?

[Paul Jurczak]

BTW, Fastor (https://github.com/romeric/Fastor) also allows for indirect indexing:

  Tensor<int,9> v{0, 1, 2, 3, 4, 5, 6, 7, 8};
  Tensor<int,3> i{6, 3, 0};
  Tensor<int,3> j{1, 2, 3};

  v(i) = v(j);

‌

[Klaus Iglberger]

Hi Paul!

Blaze approaches the problem by means of views, and in particular element selections:

blaze::DynamicVector<int> a{ 0, 1, 2, 3, 4, 5, 6, 7, 8 };

auto e = elements<6,3,0>( a );  // Select the elements 6, 3, and 0

std::cout << a << '\n' << e << '\n';

elements<1,2,3>( a ) = e;  // Assign to the elements 1, 2, and 3

std::cout << a << '\n';

Output:

( 0 1 2 3 4 5 6 7 8 )
( 6 3 0 )
( 0 6 3 0 4 5 6 7 8 )

I hope this answers your question.

Best regards,

Klaus!

[Klaus Iglberger]

Issue #400 was marked as a duplicate of this issue.