A Novel Algorithm for Reduction of Non-Deterministic Finite Automata

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@ IJTSRD | Available Online @ www ISSN No: 245 Inte R A Nove Non-De G. M Asst.Prof Depa Dadi Institute of E ABSTRACT In automata theory a minimization is transforming a given finite state mac equivalent automation that has a minimu states. Here, the reduction of Determ Automata(DFA) is very simpl Nondeterministic Finite Automata(NFA because which has maximium number of to reach new states. So a minimal NFA problem in automata theory. We conside of approximating a minimal NFA or a m expression. There are several approac minimization either without approximati or running in at least exponential time. H introducing the new NFA reduction algo minimization of NFA. This algorithm number of state transitions of Nondeterm Automata. NFA reduction algorithm also complexity of Kameda- Weiner algorithm shown empirically that this algorithm i largely reducing the memory requirem minimization algorithm. Reducing the siz using NFA Reduction Algorithm has be reduce importantly the search time. Keywords: Non Deterministic Finite Aut Simplest Automation Matrix, Simplifie Matrix (SFM), Transition table, Transition I. INTRODUCTION By NFA reduction algorithms, we mea which from a given NFA produce a smal w.ijtsrd.com | Volume – 2 | Issue – 1 | Nov-Dec 56 - 6470 | www.ijtsrd.com | Volum ernational Journal of Trend in Sc Research and Development (IJT International Open Access Journ el Algorithm for Reduction of eterministic Finite Automata Mutyalamma, K. Komali, G. Pushpa artment of Computer Science and Engineering, Engineering & Technology, Anakapalle, A.P, Ind the task of chine into an um number of ministic Finite le whereas A) is complex possible paths A is a primal er the problem minimal regular ches to NFA ion guarantees Here this paper orithm for the m will reduce ministic Finite o resolves the m. This paper is effective in ment of NFA ze of NFA by een shown to tomata (NFA), ed Functional n function. an algorithms ller equivalent NFA w.r.t. the number of st algorithms given in this paper of transitions, so that there is n complexity measure is consi Among automata which rec language L, the problem of minimal NFA w.r.t. the num shown to be NP-hard in [3]. I like in [9,13,4] are quite not aim is to provide reduction a polynomial complexity w.r.t states in the given NFA. S useful, for instance, to prevent during the determinization of either its straightforward sim based on a partial determiniz basic objects of formal lang languages and their acceptance and regular expressions. Regu lexical tokens for syntactic patterns in text manipulation basis of standard utilities suc editors or programming lang Internally regular expressio (nondeterministic) finite autom of this representation crucially time of the applied algorithms of minimizing dfa’s, which is well known that nfa or regular is computationally hard, nam [11]. Jiang and Ravikumar [8] minimization problem for nfa c 2017 Page: 1341 me - 2 | Issue 1 cientific TSRD) nal dia tates. Actually, the main r also reduce the number no ambiguity about which idered as being reduced. cognize a given regular computing one or every mber of states has been Indeed, known algorithms practicable. Our present algorithms which have a t. the initial number of Such algorithms may be t or moderate the blow up the NFA, or to speed up mulation, or its imulation zation. Among the most guage theory are regular e devices, finite automata ular expressions describe c specifications, textual systems and they are the ch as scanner generators, guages (perl, awk, php). ons are converted to mata and the succinctness y determines the running s. Contrary to the problem s efficiently possible, it is r expression minimization mely PSPACE-complete ] show moreover that the a’s or regular expressions

description

In automata theory a minimization is the task of transforming a given finite state machine into an equivalent automation that has a minimum number of states. Here, the reduction of Deterministic Finite Automata DFA is very simple whereas Nondeterministic Finite Automata NFA is complex because which has maximium number of possible paths to reach new states. So a minimal NFA is a primal problem in automata theory. We consider the problem of approximating a minimal NFA or a minimal regular expression. There are several approaches to NFA minimization either without approximation guarantees or running in at least exponential time. Here this paper introducing the new NFA reduction algorithm for the minimization of NFA. This algorithm will reduce number of state transitions of Nondeterministic Finite Automata. NFA reduction algorithm also resolves the complexity of Kameda Weiner algorithm. This paper shown empirically that this algorithm is effective in largely reducing the memory requirement of NFA minimization algorithm. Reducing the size of NFA by using NFA Reduction Algorithm has been shown to reduce importantly the search time. G. Mutyalamma | K. Komali | G. Pushpa "A Novel Algorithm for Reduction of Non-Deterministic Finite Automata" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-1 , December 2017, URL: https://www.ijtsrd.com/papers/ijtsrd8233.pdf Paper URL: http://www.ijtsrd.com/computer-science/other/8233/a-novel-algorithm-for-reduction-of--non-deterministic-finite-automata/g-mutyalamma

Transcript of A Novel Algorithm for Reduction of Non-Deterministic Finite Automata

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ISSN No: 2456

InternationalResearch

A Novel Algorithm Non-Deterministic Finite Automata

G. Mutyalamma

Asst.Prof Department of Computer Science and Engineering, Dadi Institute of Engineering & Technology, Anakapalle, A.P,

ABSTRACT

In automata theory a minimization is the task of transforming a given finite state machine into an equivalent automation that has a minimum number of states. Here, the reduction of Deterministic Finite Automata(DFA) is very simple whereas Nondeterministic Finite Automata(NFA) is complex because which has maximium number of possible paths to reach new states. So a minimal NFA is a primal problem in automata theory. We consider the problem of approximating a minimal NFA or a minimal regular expression. There are several approaches to NFA minimization either without approximation guarantees or running in at least exponential time. Here this paper introducing the new NFA reduction algorithm for the minimization of NFA. This algorithm will reduce number of state transitions of Nondeterministic Finite Automata. NFA reduction algorithm also resolves the complexity of Kameda- Weiner algorithm. This paper shown empirically that this algorithm is effective in largely reducing the memory requirement of NFA minimization algorithm. Reducing the size of NFA by using NFA Reduction Algorithm has been shown to reduce importantly the search time. Keywords: Non Deterministic Finite Automata (NFA), Simplest Automation Matrix, Simplified Functional Matrix (SFM), Transition table, Transition function. I. INTRODUCTION By NFA reduction algorithms, we mean algorithms which from a given NFA produce a smaller equivalent

@ IJTSRD | Available Online @ www.ijtsrd.com | Volume – 2 | Issue – 1 | Nov-Dec 2017

ISSN No: 2456 - 6470 | www.ijtsrd.com | Volume

International Journal of Trend in Scientific Research and Development (IJTSRD)

International Open Access Journal

A Novel Algorithm for Reduction of Deterministic Finite Automata

G. Mutyalamma, K. Komali, G. Pushpa

Asst.Prof Department of Computer Science and Engineering,

Dadi Institute of Engineering & Technology, Anakapalle, A.P, India

is the task of transforming a given finite state machine into an equivalent automation that has a minimum number of states. Here, the reduction of Deterministic Finite Automata(DFA) is very simple whereas

Finite Automata(NFA) is complex because which has maximium number of possible paths to reach new states. So a minimal NFA is a primal problem in automata theory. We consider the problem

a minimal NFA or a minimal regular expression. There are several approaches to NFA minimization either without approximation guarantees or running in at least exponential time. Here this paper introducing the new NFA reduction algorithm for the

n of NFA. This algorithm will reduce number of state transitions of Nondeterministic Finite Automata. NFA reduction algorithm also resolves the

Weiner algorithm. This paper shown empirically that this algorithm is effective in

reducing the memory requirement of NFA minimization algorithm. Reducing the size of NFA by using NFA Reduction Algorithm has been shown to

: Non Deterministic Finite Automata (NFA), Simplified Functional

Matrix (SFM), Transition table, Transition function.

By NFA reduction algorithms, we mean algorithms which from a given NFA produce a smaller equivalent

NFA w.r.t. the number of states. Actually, the main algorithms given in this paper also reduceof transitions, so that there is no ambiguity about which complexity measure is considered as being reduced. Among automata which recognize a given regular language L, the problem of computing one or every minimal NFA w.r.t. the number of states has been shown to be NP-hard in [3]. Indeed, known algorithms like in [9,13,4] are quite not practicable. Our present aim is to provide reduction algorithms which have a polynomial complexity w.r.t. the initial number of states in the given NFA. Such algorithms may be useful, for instance, to prevent or moderate the blow up during the determinization of the NFA, or to speed up either its straightforward simulation, or its imulation based on a partial determinization. Among thebasic objects of formal language theory are regular languages and their acceptance devices, finite automata and regular expressions. Regular expressions describe lexical tokens for syntactic specifications, textual patterns in text manipulation systebasis of standard utilities such as scanner generators, editors or programming languages (perl, awk, php). Internally regular expressions are converted to (nondeterministic) finite automata and the succinctness of this representation crucially determines the running time of the applied algorithms. Contrary to the problem of minimizing dfa’s, which is efficiently possible, it is well known that nfa or regular expression minimization is computationally hard, namely PSPACE[11]. Jiang and Ravikumar [8] show moreover that the minimization problem for nfa’s or regular expressions

Dec 2017 Page: 1341

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Scientific (IJTSRD)

International Open Access Journal

ndia

NFA w.r.t. the number of states. Actually, the main ven in this paper also reduce the number

of transitions, so that there is no ambiguity about which complexity measure is considered as being reduced. Among automata which recognize a given regular

, the problem of computing one or every FA w.r.t. the number of states has been

hard in [3]. Indeed, known algorithms like in [9,13,4] are quite not practicable. Our present aim is to provide reduction algorithms which have a polynomial complexity w.r.t. the initial number of

es in the given NFA. Such algorithms may be useful, for instance, to prevent or moderate the blow up during the determinization of the NFA, or to speed up either its straightforward simulation, or its imulation based on a partial determinization. Among the most basic objects of formal language theory are regular languages and their acceptance devices, finite automata and regular expressions. Regular expressions describe lexical tokens for syntactic specifications, textual patterns in text manipulation systems and they are the basis of standard utilities such as scanner generators, editors or programming languages (perl, awk, php). Internally regular expressions are converted to (nondeterministic) finite automata and the succinctness

ucially determines the running time of the applied algorithms. Contrary to the problem of minimizing dfa’s, which is efficiently possible, it is well known that nfa or regular expression minimization is computationally hard, namely PSPACE-complete

ang and Ravikumar [8] show moreover that the minimization problem for nfa’s or regular expressions

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remains PSPACE-complete, even when specifying the regular language by a dfa. The state minimization of deterministic finite automata (DFAs) is well-known but the state minimization of nondeterministic finite automata (NFAs) is more complicated. A nondeterministic finite automaton (or NFA) can be defined as a 5-tuple (Q, ∑ , T, q0 , F ) Where, -Q is a finite set of states. -∑ is the input alphabet -q0 is the initial state Where q0€Q -F is the final state Where F€Q i.e, set of final states -T: Q×∑2Q is the transition function

Nondeterministic automata allow more possible transitions with same input for each state to new state. NFA also allows epsilon as transition which means transition with epsilon does not carry any character as input to any new state. You can observe in this above example. Transition table for NFA:

Staes/inputs a b 0 {0,1} {0,1} 1 {3} Ø 2 Ø {3} 3 {3} {3}

Finite automata used to recognize and define the regular languages. Finite automata can be classified into two types- FA without output and finite automata without output. DFA,NFA,EPSILON-NFA related to FA without output. Now question is among these which is powerful language? Every language is powerful when we prove equivalence of each automata. If we

convert DFA to NFA or NFA to DFA or NFA to epsilon-NFA or epsilon-NFA to NFA all languages are powerful. DFANFA NFADFA E-NFANFA NFAE-NFA If any automata conversion is possible both are equivalent and powerful. Minimal DFA(with minimum no of states) construction is very familiar to us where as NFA is difficult to get minimal NFA because it has 2Q states. NFA's structure for regular expression with epsilon (ab)*∪(aba)*.

M=({q0, q1, q2, q3, q4, q5},{a,b},T,q0,{q1,q2}) The rearward word (w) of a word (w) {w=x1, x2.... xn} will be w= xn, xn-1… xi and if we have a language L then the rearward language of a language (L) will be L = {w|wЄi} for an automaton Z= (Q, Σ, Δ, I, F) the rearward automaton will be Z’= (Q,Σ,Δ,I,F) For a granted language L if DFA distinguishes the language and it also has the minimal possible no. of

T(q0,E){q1,q2} T(q0,{a,b}) Ø

T(q1,a){q3} T(q1,b) Ø

T(q2,a){q4} T(q2,b) Ø

T(q3,a) Ø T(q3,b){q1}

T(q4,a) Ø T(q4,b){q5}

T(q5,a) {q2} T(q5,b) Ø

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states then this type of automata is known as Orthodox Automata and for rearward language L if DFA recognize the rearward language L and it also has the minimal possible number of states then this type of automata is known as Rearward Orthodox Automata. The NFA state minimization problem can be defined as follows: find an automaton which is equivalent to given NFA with minimum possible number of states. Note that solution of this problem may not be unique II. RELATED WORK

The paper by Himanshu Pandey, V. K Singh, Amit Pandey [14] on “ A New NFA Reduction Algorithm for State Minimization Problem give a more efficient algorithm for constructing the same equivalence, together with results from a computer implementation”. We are inspired by the work of V. K Singh [1]. We are inspired by the work of Guangming Xing [1], shown that no auxiliary states can be removed without violating the describing properties of Thompson NFA in his paper “Minimized Thompson NFA”. In this paper ‘Reducing the Size of NFAs by Using Equivalences and Preorders’ Lucian llie, Roberto SolisOba, Sheng yu clubbed the concept of Eand Preorders for minimization of NFA. This article explains the minimization of nfa’s or regular expressions either for given nfa’s or regular Expressions[16]. We consider the problem of approximating nfa or a minimal regular expression. There are several approaches to nfa minimization [2,5,6,10] either without approximation guarantees or running in at least exponential time. This article explains why such guarantees cannot be expected for efficient algorithms. The classical reduction algorithms for DFAs, e.g. in [7], are based on an equivalence relation over the set of states Q which converges step by step toward the coarsest equivalence relation such that all states contained in one equivalence class have the same right language. The concept of using Hash Table for minimization of DFA is very useful concept for creating a minimal DFA. This concept is given by Vishal Garg , Anu in 2013. Yi. Liu, Taghi M. Khoshgoftaar [12] in DFA Minimizing State Machines Using Hashare inspired by the work of C. Hsiang Chan, R. Paigeb [15] overcome drawbacks of both methods with a O(r) time O(s) space algorithm to construct an O(s) space representation of McNaughton and Yamada’s NFA. Given any set V of NFA

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states then this type of automata is known as Orthodox Automata and for rearward language L if DFA

e L and it also has the minimal possible number of states then this type of automata is known as Rearward Orthodox Automata. The NFA state minimization problem can be defined as follows: find an automaton which is equivalent to given

ble number of states. Note that solution of this problem may not be unique

Himanshu Pandey, V. K Singh, Amit A New NFA Reduction Algorithm

give a more efficient algorithm for constructing the same equivalence, together with results from a computer implementation”. We are inspired by the work of V. K Singh [1]. We are inspired by the work of Guangming Xing [1], shown

an be removed without violating the describing properties of Thompson NFA in his paper “Minimized Thompson NFA”. In this paper ‘Reducing the Size of NFAs by Using Equivalences and Preorders’ Lucian llie, Roberto Solis-Oba, Sheng yu clubbed the concept of Equivalences and Preorders for minimization of NFA. This article explains the minimization of nfa’s or regular expressions either for given nfa’s or regular

approximating a minimal ession. There are several

approaches to nfa minimization [2,5,6,10] either without approximation guarantees or running in at least exponential time. This article explains why such guarantees cannot be expected for efficient algorithms.

ion algorithms for DFAs, e.g. in [7], are based on an equivalence relation over the set of

which converges step by step toward the coarsest equivalence relation such that all states contained in one equivalence class have the same right

The concept of using Hash Table for minimization of DFA is very useful concept for creating a minimal DFA. This concept is given by Vishal Garg , Anu in 2013. Yi. Liu, Taghi M. Khoshgoftaar [12] in DFA Minimizing State Machines Using Hash- Tables. We

inspired by the work of C. Hsiang Chan, R. Paigeb [15] overcome drawbacks of both methods with a O(r) time O(s) space algorithm to construct an O(s) space representation of McNaughton and Yamada’s NFA.

III. IMPLEMENTATION

By the help of NFA reduction algorithm we have to minimize the non Deterministic finite automata. If we have a NFA with following condition:

-Initial state has a self loop and incoming or outgoing transition. For that type of condition we will use NFA Reduction Algorithm. Steps of NFA Reduction Algorithm: Step1: Firstly we have to draw a transition table of given NFA (Which satisfy the following condition). Step2: Then we construct Simplest Automaton Matrix with the help of transition table. Step3: Now we draw a transition graph of following NFA with opposite transition. Step4: Next we create a transition table of rearward NFA and construct the Rearward Automaton Matrix. Step5: With the help of simplest automaton and rearward automaton matrix, we will form a Simplified Functional Matrix (SFM). Step6: The elements of the SFM is defined by the following formula

x∩y = Ǿ→ 0 x∩y = Ǿ→ 1

Step7: Now we apply these steps on the SFM table

(i) (x i∩ yi) → U (ii) (xi Ù yi) - (x(iii) j:U→ V

NFA reduction algorithm exploits unique features of the minimization NFA to achieve high throughput.We have taken a transition graph of NFA

Regular expression is: (a+b)*a(a+b)b

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IMPLEMENTATION

NFA reduction algorithm we have to minimize the non Deterministic finite automata. If we have a NFA with following condition:

Initial state has a self loop and incoming or outgoing

For that type of condition we will use NFA Reduction

Steps of NFA Reduction Algorithm:

Firstly we have to draw a transition table of given NFA (Which satisfy the following condition).

: Then we construct Simplest Automaton Matrix with the help of transition table.

: Now we draw a transition graph of following NFA with opposite transition.

Next we create a transition table of rearward NFA and construct the Rearward Automaton Matrix.

With the help of simplest automaton and we will form a Simplified

: The elements of the SFM is defined by the

Now we apply these steps on the SFM table → U

(xi∩yi)→V

NFA reduction algorithm exploits unique features of the minimization NFA to achieve high throughput. We have taken a transition graph of NFA

Regular expression is: (a+b)*a(a+b)b

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Table 1: Transition Table of given Diagram

states I/P=a I/P=bq0 {q0,q1} {q0}q1 {q2} {q2}q2 Ǿ {q3}q3 Ǿ Ǿ

Table 2: Simplest Automation Matrix

states I/P=a I/P=bq0 {q0,q1} {q0}{q0,q1} {q0,q1,q2} {q0,q2}{q0,q2} {q0,q1} {q0,q3}{q0,q3} {q0,q1} {q0}{q0,q1,q2} {q0,q1,q2} {q0,q2,q3}

Diagram of NFA with opposite transition

Table 3: Transition table of rearward NFA

states I/P=a I/P=bq0 {q0} {q0}q1 {q0} Ǿ q2 {q1} {q1}q3 {q2} Ǿ

Table 4: Rearward Automation matrix

states I/P=a I/P=bq0 {q0} {q0}

For creating SFM table we will take the state column of simplest automation matrix and for SFM rows we will take the state column of rearward automation matrix.

Table 5: Simplified Functional Matrix(SFM)

Xi/yi {q0} q0 {q0} {q0,q1} {q0} {q0,q2} {q0} {q0,q3} {q0} {q0,q1,q2} {q0}

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Table 1: Transition Table of given Diagram

I/P=b {q0} {q2} {q3}

Table 2: Simplest Automation Matrix

I/P=b {q0} {q0,q2} {q0,q3} {q0} {q0,q2,q3}

with opposite transition

Table 3: Transition table of rearward NFA

I/P=b {q0}

{q1}

I/P=b {q0}

For creating SFM table we will take the state column of simplest automation matrix and for SFM rows we will take the state column of rearward automation matrix.

Table 5: Simplified Functional Matrix(SFM)

6. The elements of the SFM is defined by the following formula x∩y= Ǿ→ 0 x∩y= Ǿ→ 1 7. Now we apply these steps on the SFM table Steps are: (i) (xi∩yi) → U (ii) (xiÙyi) - (xi∩yi)→V (iii) j:U→ V [1] (xi ∩ yi) →(q0∩q0) → q0=U

(xiÙyi) - (xi∩yi)→(q0Ùq0)U→V means q0→q0 Now we check that transition (1in the original NFA. We can see that transition (1→1) is exist, so the transition graph will be,

[2] (xi∩yi) → {(q0,q1) ∩(q0)} [(xiÙyi)- (xi∩yi)] →{[(q0,q1)→q1=V U→V means q0→q1 Now we check that transition (q0in the original NFA. We can see that transition (q0→q1) is exist, so the transition graph will be,

[3] (xi∩yi) →{(q0,q2) ∩(q0)} → q0=U [(xiÙyi)- (xi∩yi)] →{[(q0,q2)U(q0)]→q2=V U→V means q0→q2 But there is no transaction between state 1 and state 3 in given NFA. So the minimal NFA will be same as above. [4] (xi∩yi) →{(q0,q3) ∩(q0)} → q0=U [(xiÙyi)- (xi∩yi)] →{[(q0,q3)U(q0)]→q3=V U→V means q0→q3 But there is no transaction between state 1 and state 3 in given NFA. So the minimal NFA will be same as above.

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6. The elements of the SFM is defined by the following

7. Now we apply these steps on the SFM table

→(q0∩q0) → q0=U Ùq0)-(q0∩q0) →q0=V

Now we check that transition (1→1) is exist or not in the original NFA. We can see that transition

exist, so the transition graph will be,

)} →q0=U →{[(q0,q1)Ù(q0)]-[(q0,q1)∩q0]

Now we check that transition (q0→q1) is exist or not in in the original NFA. We can see that transition

→q1) is exist, so the transition graph will be,

→{(q0,q2) ∩(q0)} → q0=U →{[(q0,q2)U(q0)]-[(q0,q2)∩q0]}

But there is no transaction between state 1 and state 3 in given NFA. So the minimal NFA will be same as

→{(q0,q3) ∩(q0)} → q0=U →{[(q0,q3)U(q0)]-[(q0,q3)∩q0]}

But there is no transaction between state 1 and state 3 in given NFA. So the minimal NFA will be same as

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[5]. (xi∩yi) →{(q0,q1,q2) ∩(q0)} →q0=U [(xiÙyi)-(xi∩yi)]→{[(q0,q1,q2)U(q0)]-[(q0,q1,q2)∩(q0)]}→ (q1,q2)=V U→V means q0→(q1,q2) We have a transition b/w state q0&q1 but there is no transition between state q0 and state q2 in original NFA. So the final minimal NFA will be:

Algorithm: NFA Reduction Algo Require NFA X 1. Construct Simplest Automaton Matrix and

Rearward Automaton Matrix. 2. Construct Simplified Functional Matrix (SFM). 3. Find all the exits combination with the help of these

function, (xi∩yi) → U (xiÙyi) - (xi∩yi)→V j:U→ V

4. Find minimum legitimate cover(s) ofconstruct minimum state NFA(s). Ensure: Minimum state NFA(s) equivalent to

IV. CONCLUSION We would like to mention first that these reduction techniques work well with some slightly different definitions of automata, like labeled transition systems with finite recognition, which are automata without final states. Recognized words are words thatcause a deadlock. Our opinion is that the most interesting algorithm is the one based on the firstapproximation, which has a reasonable worst case complexity, and should prove to be very fast in practice. To our knowledge, this algorithm is the most efficient one in this level of performance. Higherapproximations may be useful if one really cares about the succinctness of the NFA. In the present paper we have considered new Reduction algorithms for NFA state minimization problem which is known to be computationally hard. These algorithms are widely used in combinatorial optimization. The essential feature of the proposed algorithm is that the most time

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→{(q0,q1,q2) ∩(q0)} →q0=U

We have a transition b/w state q0&q1 but there is no transition between state q0 and state q2 in original

Algorithm: NFA Reduction Algorithm

Construct Simplest Automaton Matrix and

Construct Simplified Functional Matrix (SFM). Find all the exits combination with the help of these

legitimate cover(s) of SFM and

Minimum state NFA(s) equivalent to A

We would like to mention first that these reduction techniques work well with some slightly different definitions of automata, like labeled transition systems with finite recognition, which are automata without final states. Recognized words are words that do not cause a deadlock. Our opinion is that the most interesting algorithm is the one based on the first-order approximation, which has a reasonable worst case complexity, and should prove to be very fast in

s the most efficient one in this level of performance. Higher-order approximations may be useful if one really cares about the succinctness of the NFA. In the present paper we have considered new Reduction algorithms for NFA

h is known to be computationally hard. These algorithms are widely used in combinatorial optimization. The essential feature of the proposed algorithm is that the most time

consuming part of the exact algorithm is replaced with fast local search function. Numerical experiments have shown that such type of concept is much less time consuming and allows obtaining acceptable results. In the future we plan to concentrate on the other time consuming algorithm. REFERENCES 1. Lucian llie, Roberto Solis

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