# Multiply by Matrix

Matrix multiplexer/multiplier: y(k) = A x(k)

This block is similar to Multiply Const, the difference being it can handle several inputs and outputs, and the input-to-output relation can be described by the following mathematical equation: y(k) = A x(k) where y in R^n, x in R^m, A in R^n*m

y(k) and x(k) are column-vectors describing the elements on the input port at time step k(this is a sync block with no memory).

Examples for where to use this block include:

- Switch matrices (i.e. switch which ports go where), assuming all ports run on the same rate
- Simulation of static MIMO-Channels (in that case, A is the channel matrix)
- Summing up streams with variable coefficients

This block as one input message port. A message sent to this port will be converted to a std::vector<std::vector<T> >, and then passed on to set_A(). If no conversion is possible, a warning is issued via the logging interface, and A remains unchanged.

Note : It is not possible to change the dimension of the matrix after initialization, as this affects the I/O signature! If a matrix of invalid size is passed to the block, an alert is raised via the logging interface, and A remains unchanged.

## Parameters[edit]

(*R*): *Run-time adjustable*

- Matrix A (
*R*) - The matrix

- TPP
- The tag propagation policy. When setting the tag propagation policy to Matrix-defined, a tag is propagated from input k to output l, if A(l,k) != 0.

## Example Flowgraph[edit]

Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI. Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately. The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.

## Source Files[edit]

- C++ files
- [1]

- Header files
- [2]

- Public header files
- [3]

- Block definition
- [4]