labview improving performance

8/6/2019 Labview Improving Performance

1/46

1

Improving the Performance of Your

NI LabVIEW Applications

Dan Hedges

Senior Software EngineerLabVIEW Performance Group


2/46

2

Agenda

How to find performance problems

Benchmarking

Profiling

Understanding LabVIEW under the hood

Memory usage

Execution system


3/46

3

Optimization Cycle

Benchmark Evaluate Performance

Identify Problem Areas

Optimize Improve efficiency

Improve Speed


4/46

4

Benchmarking Code Execution

Timing Template (data dep) LabVIEW Shipping Example


5/46

5

Benchmarking Code Execution

Calibration Code

Analysis

Benchmark Project LabVIEW Real-Time Shipping Example


6/46

6

Tools for Measuring Resource Usage

(Windows) Task Manager

Perfmon


7/467

Windows Task ManagerGives user a rough idea ofwhether memory or CPU isthe bottleneck

Can be helpful inidentifying memory leaks

ViewSelect Columns

allows you to add additionalstats


8/468

PerfmonAllows you to monitor

ProcessorsDisk I/ONetwork Tx/Rx

Memory/Paging

Access by typingperfmon into the

Windows Run dialog


9/469

Why Should You Profile Your VIs?

Performance improvements are most effective in

the 20 percent Guessing which 20 percent is difficult

80 percent of the execution time is spent in

20 percent of the code

The 80/20 rule of software performance


10/4610

VI Profiler

Tools >> Profile >> Performance and Memory


11/4611

Demo VI Profiling


12/4612

LabVIEW Desktop Execution Trace

Toolkit

Threads, CPU

and Memory

VIs

MultipleSessions

Detailed

execution

traces

Thread and VIinformation

Measurement

of execution

time


13/46

13

Profiling and Benchmarking Summary

To answer this question: Use these tools:

What is my current performance? Benchmark VIs

What are my limiting resources? Task Manager, Perfmon

How much time are each of my VIs taking? VI Profiler

In what order are events occurring? LabVIEW Desktop Execution Trace Toolkit


14/46

14

UnderLabVIEWs Hood

MemoryManagement ExecutionSystem


15/46

15

What Is In Memory?

Panel Diagram

CompiledCode Data


16/46

16

VIs in Memory

When a VI is loaded into memory

We always load the data

We load the code if it matches our platform(x86 Windows, x86 Linux, x86 Mac, PowerPC Mac)

We load the panel and diagram only if we need to

(for instance, we need to recompile the VI)


17/46

17

Panel and Diagram Data

How many bytes of memory does this VI use?

The answer depends on:

Is the panel in memory?

Is the environment multi-threaded?


18/46

18

Execute, Operate and Transfer Data

Populated byCode

4K ExecuteData

Copy for Indicator4K Operate

Data

TemporaryBuffer

4K TransferData


19/46

19

Avoid Loading Panels, Save Memory


20/46

20

Wire Semantics Every wire is a buffer

Branches typically create copies


21/46

21

Optimizations by LabVIEW

The theoretical 5 copies become 1 copy operation

Copy

Output is in place with input


22/46

22

The In Place Algorithm

Determines when a copy needs to be made

Weighs arrays and clusters higher than other types

Algorithm runs during compilation, not execution

Does not know the size of an array or cluster

Relies on the sequential aspects of the program

Branches may require copies


23/46

23

Bottom Up

In-place information is propagated bottom up

Increments array in plac

Copy because

of increment No copies required

Branched wire


24/46

24

Showing Buffer Allocations


25/46

25

The In-Place Element Structure

Allows you to explicitly modify data in place


26/46

26

Example of In Place OptimizationOperate on each element of an array of waveforms


27/46

27

Make the First SubVI In Place

changes into


28/46

28

SubVI 2 Is Made In Place

Changes into


29/46

29

SubVI 3 Is Made In Place

Changes into


30/46

30

Final Result: Dots Are Hidden


31/46

31

Building Arrays

There are a number of ways to build arrays and

some are better than others

BadReallocates array memory onevery loop iteration

No compile time optimization


32/46

32

Building Arrays

There are a number of ways to build arrays. Try to

minimize reallocations.

BestMemory preallocated

Indexing tunnel eliminates

need for copies


33/46

33

Demo Effects of MemoryOptimization


34/46

34

UnderLabVIEWs Hood

MemoryManagement ExecutionSystem


35/46

35

VIs Are Compiled001110100101010100010001111110101010101000101110001011001011001100011101001010

10100010001111110101010101000101110001011001011001100011101001010101000100011111101010101010001011100010


36/46

36

VIs Are Compiled: ClumpsClump 1

Clump 2

Clump 0 Clump 0


37/46

37

Clump 2 Sleeping

Clump 1 Sleeping

Clump 0 Sleeping

VIs Are Compiled: Clumps

Completion of diagram:

Divide nodes, display of

indicators, then VI exit

Start of diagram:

Reads controls, then

schedules Clumps 1

and 2

Then sleeps ...

Bottom for loopindicator is updated

Clump 0 Scheduled

Sleep ...

Top for loop

indicator is updated

Clump 0 Scheduled

Sleep ...

Clump 0 Clump 1

Clump 2

Clump 0


38/46

38

Single-Threaded LabVIEW

CPU Thread

User Interface

Loop

CodeExecution

Coroutines


39/46

39

Exec

Thread

Multithreaded LabVIEW

CPU

UI Loop

Thread

Exec

Thread

messages

Exec

Thread

Exec

Thread


40/46

40

Exec

Thread

LabVIEW on a Multicore Machine

CPU1

UI Loop

Thread

Exec

Thread

Exec

Thread

Exec

Threadmessages

CPU0


41/46

41

Some Operations Require the UI

Thread

Call Library Nodes

Control/Indicator Property Nodes

Front Panel Control References


42/46

42

Execution Properties


43/46

43

Reentrant VIs

Reentrancy allows one subVI to be called

simultaneously from different places

Requires extra memory for each instance

Use reentrant VIs in two different cases

To allow a subVI to be called in parallel

To allow a subVI instance to maintain its own state


44/46

44

LabVIEW 2010 Compiler

Generates code that runs faster, ~30%

Takes longer to run (~5x-7x)

SSEInstructions

SubVI InlinerRegister

CandidatesDead CodeElimination

Loop InvariantCode Motion

Common

SubexpressionElimination

And more


45/46

45

Demo Effects of ExecutionOptimization


46/46

Next Steps

LabVIEW Help

In LabVIEW

ni.com/multicore

ni.com/devzone

On the Web

labview improving performance

Documents