next up previous print clean
Next: Adjoint derivative Up: Basic operators and adjoints Previous: Programming linear operators

FAMILIAR OPERATORS

The simplest and most fundamental linear operators arise when a matrix operator reduces to a simple row or a column.

A row    is a summation operation.

A column is an impulse response.

If the inner loop of a matrix multiply ranges within a

row,    the operator is called sum or pull.

column, the operator is called spray or push.

A basic aspect of adjointness is that the adjoint of a row matrix operator is a column matrix operator. For example, the row operator [a,b]
\begin{displaymath}
y \eq
\left[ \ a \ b \ \right] 
\left[
\begin{array}
{l}
 x_1 \\  x_2\end{array}\right] 
\eq
a x_1 + b x_2\end{displaymath} (1)
has an adjoint that is two assignments:
\begin{displaymath}
\left[
 \begin{array}
{l}
 \hat x_1 \\  \hat x_2
 \end{array...
 ...q
 \left[
 \begin{array}
{l}
 a \\  b
 \end{array} \right]
 \ y\end{displaymath} (2)

The adjoint of a sum of N terms is a collection of N assignments.