# Dot Product (G Dataflow)

Version:
Last Modified: January 12, 2018

Computes the dot product of two vectors.

## reset

A Boolean that specifies whether to reset the internal state of the node.

 True Resets the internal state of the node. False Does not reset the internal state of the node.

This input is available only if you wire a double-precision, floating-point number or a complex double-precision, floating-point number to vector x or vector y.

Default: False

## vector x

First input vector.

This input accepts the following data types:

• Double-precision, floating-point number
• Complex double-precision, floating-point number
• 1D array of double-precision, floating-point numbers
• 1D array of complex double-precision, floating-point numbers

When vector x is a 1D array of double-precision, floating-point numbers or a 1D array of complex double-precision, floating-point numbers, the number of elements in the first input vector must be greater than 0 and equal to the number of elements in the second input vector. Otherwise, the dot product is undefined, and the node returns NaN.

## vector y

Second input vector.

This input accepts the following data types:

• Double-precision, floating-point number
• Complex double-precision, floating-point number
• 1D array of double-precision, floating-point numbers
• 1D array of complex double-precision, floating-point numbers

When vector y is a 1D array of double-precision, floating-point numbers or a 1D array of complex double-precision, floating-point numbers, the number of elements in the first input vector must be greater than 0 and equal to the number of elements in the second input vector. Otherwise, the dot product is undefined, and the node returns NaN.

## sample length

Length of each set of data. The node performs computation for each set of data.

This input is available only if you wire a double-precision, floating-point number or a complex double-precision, floating-point number to vector x or vector y.

Node Behavior with Different sample length Values

When you set sample length to zero, the node calculates a cumulative solution for the input data from the time the node is called or initialized. When sample length is greater than zero, the node calculates the solution for only the newest set of input data.

Default: 100

## error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

The dot product.

## error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

## Algorithm for Calculating the Dot Product

Let x represent the input sequence vector x and y represent the input sequence vector y. This node calculates the output dot product using the following equation.

$\text{dot product}=\underset{i=0}{\overset{n-1}{\sum }}{x}_{i}{y}_{i}^{*}$

where n is the number of data points and yi* is the complex conjugate of yi. Notice that the output dot product is a scalar value.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application