Método Gert

'

NASr-

21(08)

MEMORANDUM RM-4973-NASA APRIL 1966

GERT"

GRAPHICAL AND REVIEW

EVALUATION TECHNIQUE
A. A. B. Pritsker

This research is sponsored by the National Aeronautics and Space Administration Contract No. NASr-21. This report does not necessarily represent the views National Aeronautics and Space Administration.

under of the

1700

MAIN

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•

SANTAMONICA

•

CALIFORNIA

,

90408

PRECESING

PAGE

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-iii-

NOT

FILMED.

PREFACE

This the Space of be the Apollo

Memorandum, Checkout

one Study under

of for

a

series

done

by

The

RAND

Corporation

on and

Headquarters,

National

Aeronautics from a

Administration terminal on

Contract of

NASr-21(08), space the

evolvedstudy to counta

countdown separately, as for

an Apollo

system. that in

That

study,

reported can for that be

developed a network; analyzing of

concept concept

a terminal turn created

down need ties (2) not

represented

this

a procedure had

(I)

networks

that

contained with an them,

activiand was two

a probability the plausibility but a random byoccurrence that the

associated to perform

treating

time

activity these The

a constant, were research

variable. the term

Networks

containing networks."

elements of the

described on this

"stochastic in

result is GERT

problem, Review

presented Technique),

this

Memorandum, for

(Graphical of

Evaluation networks. be

and

a procedure

theanalysis

stochastic GERT can

a powerful associated types

tool

for

the

systems and GERT

analyst provides has wide

since an

it has

all

the

advantages of

with of by

networks

exact

evaluation

certain as

networks. the numerous

application in this as a

possibilities, Memorandum, teaching The His and

indicated has

examples make

givenalso

characteristics

which

it useful

mechanism. author of this Memorandum is with in the is a consultant State of to The RAND where Corporation. he is a

primary of

association the faculty

Arizona

University,

member

Department

Industrial

Engineering.

i'_'ECEE;ING

PAGE BLANK NOT I=IL_ED.

SUMMARY

GERT,

an

acronym for the

for

Graphical ofand or

Evaluation

and

Review

Technique, of

is a procedure EXCLUSIVE-OR, branches are

study

stochastic AND nodes In

networks (vertices)

composed and of

INCLUSIVE-OR,

multiparameter the network the

(transmittances by two

edges).

GERT, (I)

branches

described is

or more and taken. into for (2) A

parameters: the time (or

a probability attribute)that to that

branch the

traversed; if it is

other

traverse combines nodes, the

branch two

transformation parameter. of

is developed For

these

parameters is derived of of the

a single

EXCLUSIVE-OR in terms of

a method probability function of has

the an

evaluation output

networks and the

realizing time

node,

moment The the

generating totalconcept method

to realize the

the output

node. and

stochastic been For

networks, GERT.

transformation,

evaluation

labeled

EXCLUSIVE-OR are program nodes, are are random has

logic

nodes,

even GERT

if

the

times yields such

associated an exact

with solution. For the

the A

branches

variables, been written and in As

still

computer logicto obtain computational

solutions. still

other These

conceptual discussed outlined. with

problems and

exist. and

problems

this Memorandum part of the

approaches and

approximations process of

evaluation a sensitivity

review analysis

associated

stochastic is included research in

networks, with GERT.

stochastic In

networks the

performing could be...