Improving the Performance of Your NI LabVIEW Applications

8/10/2019 Improving the Performance of Your NI LabVIEW Applications

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Improving the Performance of Your

NI LabVIEW A lications


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Improving Performance in

LabVIEW

Optimization Tools Optimization


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Optimization Cycle

OptimizeBenchmark mprove e c ency

Improve speed

va uate per ormance

Identify problem areas


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Why Should You Profile Your VIs?

80 percent of the execution time is

s ent in 20 ercent of the code

The 80/20 rule of software performance

Performance improvements are most

effective in the 20 percent

Guessing which 20 percent is difficult


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LabVIEW



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Windows Task Manager

Gives user a rough idea of

whether memory or CPU is

the bottleneck

Can be hel ful inidentifying memory leaks

ViewSelect Columns

allows you to add additional

stats


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Perfmon

Allows you to monitor

Processors

Disk I/O

Network Tx/Rx

Memor /Pa in

Access by typing

perfmon into the

Windows Run dialog


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Benchmarking Code Execution

Timing Template (data dep) LabVIEW Shipping Example


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Benchmarking Code Execution

Code

Calibration

Analysis

Benchmark Project LabVIEW Real-Time Shipping Example


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VI Profiler

Timing and memory statistics for VIsToolsProfilePerformance and Memory


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LabVIEW Desktop Execution Trace

Toolkit

Multiple

Detailed

execution

traces

Thread and VI

information,

and Memory

VIs

ess ons Measurement

of execution

time


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Benchmarking Summary

OS Level

Task Manager, Perfmon

LabVIEW Level VI Profiler, Benchmark VIs

VI Level

LabVIEW Desktop Execution Trace Toolkit


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LabVIEW



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VI Components

Panel

Diagram

Code

Data

Control/indicator values

Default data

Block diagram constant data


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VIs in Memory

When a VI is loaded into memory

We always load the data

We load the code if it matches our platform

, , ,We load the panel and diagram only if we need to

(for instance, we need to recompile the VI)


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Panel and Diagram Data

Front panel controls and indicators need their owncopy of the data to display, called operate data

This VI uses about 8 KB of data if the panel is open,

and about 4 KB otherwise


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LabVIEW Terminology

Panel data is called Operate Data

Controls and indicators have their own copy of the

data, so that front panel editing of data does not

interfere with com utations in the dia ram Diagram data is called Execution Data

Every wire represents a buffer of data

Transfer Data is used to copy between them

Avoids multithreading issues


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Memory Performance

The following features affect the impact

memory allocation has on your application:

Wire Semantics and In Placeness

Passing values to subVIs

Shift registers

Front panel indicators


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Wire Semantics

Every wire is a buffer Branches typically create copies


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Optimizations by LabVIEW

The theoretical 5 copies become 1 copy operation

Copy

Output is in place with input


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The In Place Algorithm

Determines when a copy needs to be made

Weighs arrays and clusters higher than other

types

Does not know the size of an array or cluster

Relies on the sequential aspects of the

program

Branches may require copies


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Bottom Up

In-place information is propagated bottom up

Branched wire

Increments array in place

Copy becauseof increment No copies required


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Allows you to explicitly modify data in place

The In-Place Element Structure


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Types of Border Nodes

Array index/replace element

Array split/replace subarray

Unbundle/bundle

Variant to/from G data

Simple in place relationship

Data value reference

read/write


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Operate on each element of an array of waveforms

Example of In Place Optimization


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Make the First SubVI In Place

changes into


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SubVI 2 Is Made In Place

Chan es into


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SubVI 3 Is Made In Place

Changes into


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Final Result: Dots Are Hidden


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Type Coercion

Changing the data type of a wire to match

the required data type

Dots indicate automatic coercion

Coercion Dot


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Passing Values to SubVIs

SubVI does not always have to make a copy

Best when

Inputs are required

In uts and out uts are not in structuresInputs and outputs are in place


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Passing Values to SubVIs

Parameters within structures causeunnecessary copies

ove


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Shift Registers

Single left input always in place with rightoutput

Even better when the body is in place

Always In Place


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Building Arrays

There are a number of ways to build arrays

and some are better than others

Reallocates array memory on

every loop iteration

No compile time optimization


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Building Arrays



Keep graphics

below the text

and to the right.

Memory allocated at load time

Values populated in place


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Building Arrays



Memory preallocated

Indexing tunnel eliminates

need for copies


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Build Array Ordering

Appending to the end of an array is much

beginning

If you need to insert items at the beginning,

insert at the end instead and use a single

Reverse Array when finished


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Demo Effects of Memory

Optimization


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LabVIEW

Purpose ofOptimization

Profiling Tools Memory

Optimization

Decrease memory usage, increase speed 80/20 Rule


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LabVIEW



Optimization

Windows Tools (Task Manager, perfmon) VI Profiler

Real-Time Execution Trace Toolkit


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LabVIEW



Optimization

Hide the dots Take advantage of in placeness


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Next Steps

LabVIEW Help

In LabVIEW

ni.com/multicore

ni.com/devzone

On the Web


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Next Steps

Visitni.com/training

Identify your current expertise level and

desired level

Register or appropriate courses

Improving the Performance of Your NI LabVIEW Applications

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