8th Annual Tcl/Tk Conference

29 July 2001Ronald A. BowersRobert G. ParkerPaul J. TanenbaumU.S. Army Research LaboratorySurvivability/Lethality Analysis Directorate

Tcl/Tk in Survivability Modelingfor Military Systems

What We Do

• Our mission is to analyze the survivability of Army systems against a wide variety of threats, including ballistic threats such as bullets, missiles, and bursting artillery rounds, as well as electronic, chemical, and biological threats.

• Testing is very expensive and can be dangerous; therefore, we use modeling extensively.

• For ballistic threats, the primary analysis model is a program called MUVES.

• Ballistic analysis requires knowledge of the target geometry, which is captured using a tool called BRL-CADTM.

BRL-CAD Primitive Shapes

wedge

cylinder

block

(wedge block) cylinder

wedge block cylinder

block (wedge cylinder)

CSG Boolean Operations

Some Pieces of a BRL-CAD Database

All primitives

shown.

Primitives found by

query ray.

BRL-CAD Software Libraries

libbn Numerical computation, quaternions, wavelets, ...

libbu Utilities: memory mgmt, parallel processing, ...

libdm Display manager: X, OGL, PostScript, ...

librt Ray tracing

libpng PNG

libz Data compression

libtcl Tcl

libtk Tk

libitcl [incr Tcl/Tk] and [incr Widgets]

Object Orientation

• Initially we packaged instances of library objects as Tcl commands.

tclsh> wdb_open db scene.g

db

tclsh> db ls

LIGHT cone.r/R light.r/R

tor.r/R all.g/ cone.s

platform.r/R box.r/R ellipse.r/R

platform.s box.s ellipse.s

tor

Object Orientation

• Now we are wrapping those objects in [incr Tcl] classes.

itcl::class Db {

protected variable db ""

public variable dbfile ""

constructor {filename} {

set dbfile $filename

set db [subst $this]_db

wdb_open $db $dbfile

}

destructor {} { rename $db "" }

public method ls {args} { eval $db ls $args } }

MUVES

• MUVES is a tool for vulnerability/lethality analysis—stochastic and deterministic—of ballistic threats against ground and air systems.

• MUVES consists of 410,000 lines of C code, including graphical user interface and general-purpose packages.

•

Targetgeometry

Personneldata

Component vulnerability

Criticalityanalysis

Behind-armor debris

Impact conditions

Threat characterization

Residual penetrationPersonnel incapacitationComponent damageSubsystem capabilitiesRemaining system utilityUser-defined criteria

...

MUVES

MUVESinputs & outputs

Pcd/h

v

mv

glacisarmor

armor-piercingrounds

HEround

firewall

enginestarter

transmissionsump

fan reararmor

A Ray-Tracing Application: Shotlining

DMUVES

• Distributed MUVES (DMUVES) is an enhancement to MUVES that enables an analysis to be run in parallel on a single computer and distributed upon multiple networked computers.

The Original MUVES Architecture

raytracerBRL-CAD

Target Description

Analyzer

Final Results File

Threats File

Pipe

View File

raytracer

raytracer

raytracer

Other Input Files Ray Requests

Ray Results

Run times were horrific, but converting the analyzer into a multithreaded application was deemed too costly.

Boss

Input Files

MUVES GUI

The DMUVES Approach

daemon

daemon

Host A

Host B

Host C

Workers

The Use of Tcl in DMUVES

daemonIfTask Manager

daemon

workerIf

Tcl Event Handler

FinalResults

File

Tcl

scr

ipts

ove

r so

cket

s

The workers also use Tcl event handlers to monitor their socket connections.

Boss

Worker

ResultsManager

The daemon is written entirely in [incr Tcl].

Performance Results

2880

920

210 130 95 250

500

1000

1500

2000

2500

3000

3500

1 3 12 24 48 96

Number of Workers

Run

Tim

e (m

inut

es)

.

Brake control rod (left)

Syncro brake crank

Syncro brake rod

Syncro mechanism

Brake crank

Brake control rod

Brake pedal lever

Brake control rod (right)

Braking controls

MUVES System Evaluation

Lessons Learned

• Developing portable GUIs is far easier with Tcl/Tk than with other packages such as Java Swing, MFC, Motif, Athena, and raw X.

• Use [incr Tcl/Tk].

• Get Tcl/Tk training early.

Plans

• BRL-CAD– Gradually replace first-generation Tcl code with [incr Tcl].

– Implement object-oriented geometry?

• MUVES– Wrap additional MUVES functions.

– Continue transitioning tools from X to Tk.

– Replace ASCII boss-to-worker messages with binary.

– Add additional boss and worker tasks,

including tasks expressed in Tcl.

– Couple MUVES parameters to Tcl variables.