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Theorem algcvg 14081
Description: One way to prove that an algorithm halts is to construct a countdown function  C : S --> NN0 whose value is guaranteed to decrease for each iteration of  F until it reaches  0. That is, if  X  e.  S is not a fixed point of  F, then  ( C `  ( F `  X ) )  <  ( C `
 X ).

If  C is a countdown function for algorithm  F, the sequence  ( C `  ( R `  k ) ) reaches  0 after at most  N steps, where  N is the value of  C for the initial state  A. (Contributed by Paul Chapman, 22-Jun-2011.)

Hypotheses
Ref Expression
algcvg.1  |-  F : S
--> S
algcvg.2  |-  R  =  seq 0 ( ( F  o.  1st ) ,  ( NN0  X.  { A } ) )
algcvg.3  |-  C : S
--> NN0
algcvg.4  |-  ( z  e.  S  ->  (
( C `  ( F `  z )
)  =/=  0  -> 
( C `  ( F `  z )
)  <  ( C `  z ) ) )
algcvg.5  |-  N  =  ( C `  A
)
Assertion
Ref Expression
algcvg  |-  ( A  e.  S  ->  ( C `  ( R `  N ) )  =  0 )
Distinct variable groups:    z, C    z, F    z, R    z, S
Allowed substitution hints:    A( z)    N( z)

Proof of Theorem algcvg
Dummy variable  k is distinct from all other variables.
StepHypRef Expression
1 nn0uz 11128 . . . 4  |-  NN0  =  ( ZZ>= `  0 )
2 algcvg.2 . . . 4  |-  R  =  seq 0 ( ( F  o.  1st ) ,  ( NN0  X.  { A } ) )
3 0zd 10888 . . . 4  |-  ( A  e.  S  ->  0  e.  ZZ )
4 id 22 . . . 4  |-  ( A  e.  S  ->  A  e.  S )
5 algcvg.1 . . . . 5  |-  F : S
--> S
65a1i 11 . . . 4  |-  ( A  e.  S  ->  F : S --> S )
71, 2, 3, 4, 6algrf 14078 . . 3  |-  ( A  e.  S  ->  R : NN0 --> S )
8 algcvg.5 . . . 4  |-  N  =  ( C `  A
)
9 algcvg.3 . . . . 5  |-  C : S
--> NN0
109ffvelrni 6031 . . . 4  |-  ( A  e.  S  ->  ( C `  A )  e.  NN0 )
118, 10syl5eqel 2559 . . 3  |-  ( A  e.  S  ->  N  e.  NN0 )
12 fvco3 5951 . . 3  |-  ( ( R : NN0 --> S  /\  N  e.  NN0 )  -> 
( ( C  o.  R ) `  N
)  =  ( C `
 ( R `  N ) ) )
137, 11, 12syl2anc 661 . 2  |-  ( A  e.  S  ->  (
( C  o.  R
) `  N )  =  ( C `  ( R `  N ) ) )
14 fco 5747 . . . 4  |-  ( ( C : S --> NN0  /\  R : NN0 --> S )  ->  ( C  o.  R ) : NN0 --> NN0 )
159, 7, 14sylancr 663 . . 3  |-  ( A  e.  S  ->  ( C  o.  R ) : NN0 --> NN0 )
16 0nn0 10822 . . . . . 6  |-  0  e.  NN0
17 fvco3 5951 . . . . . 6  |-  ( ( R : NN0 --> S  /\  0  e.  NN0 )  -> 
( ( C  o.  R ) `  0
)  =  ( C `
 ( R ` 
0 ) ) )
187, 16, 17sylancl 662 . . . . 5  |-  ( A  e.  S  ->  (
( C  o.  R
) `  0 )  =  ( C `  ( R `  0 ) ) )
191, 2, 3, 4algr0 14077 . . . . . 6  |-  ( A  e.  S  ->  ( R `  0 )  =  A )
2019fveq2d 5876 . . . . 5  |-  ( A  e.  S  ->  ( C `  ( R `  0 ) )  =  ( C `  A ) )
2118, 20eqtrd 2508 . . . 4  |-  ( A  e.  S  ->  (
( C  o.  R
) `  0 )  =  ( C `  A ) )
2221, 8syl6reqr 2527 . . 3  |-  ( A  e.  S  ->  N  =  ( ( C  o.  R ) ` 
0 ) )
237ffvelrnda 6032 . . . . 5  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( R `  k
)  e.  S )
24 fveq2 5872 . . . . . . . . 9  |-  ( z  =  ( R `  k )  ->  ( F `  z )  =  ( F `  ( R `  k ) ) )
2524fveq2d 5876 . . . . . . . 8  |-  ( z  =  ( R `  k )  ->  ( C `  ( F `  z ) )  =  ( C `  ( F `  ( R `  k ) ) ) )
2625neeq1d 2744 . . . . . . 7  |-  ( z  =  ( R `  k )  ->  (
( C `  ( F `  z )
)  =/=  0  <->  ( C `  ( F `  ( R `  k
) ) )  =/=  0 ) )
27 fveq2 5872 . . . . . . . 8  |-  ( z  =  ( R `  k )  ->  ( C `  z )  =  ( C `  ( R `  k ) ) )
2825, 27breq12d 4466 . . . . . . 7  |-  ( z  =  ( R `  k )  ->  (
( C `  ( F `  z )
)  <  ( C `  z )  <->  ( C `  ( F `  ( R `  k )
) )  <  ( C `  ( R `  k ) ) ) )
2926, 28imbi12d 320 . . . . . 6  |-  ( z  =  ( R `  k )  ->  (
( ( C `  ( F `  z ) )  =/=  0  -> 
( C `  ( F `  z )
)  <  ( C `  z ) )  <->  ( ( C `  ( F `  ( R `  k
) ) )  =/=  0  ->  ( C `  ( F `  ( R `  k )
) )  <  ( C `  ( R `  k ) ) ) ) )
30 algcvg.4 . . . . . 6  |-  ( z  e.  S  ->  (
( C `  ( F `  z )
)  =/=  0  -> 
( C `  ( F `  z )
)  <  ( C `  z ) ) )
3129, 30vtoclga 3182 . . . . 5  |-  ( ( R `  k )  e.  S  ->  (
( C `  ( F `  ( R `  k ) ) )  =/=  0  ->  ( C `  ( F `  ( R `  k
) ) )  < 
( C `  ( R `  k )
) ) )
3223, 31syl 16 . . . 4  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( C `  ( F `  ( R `
 k ) ) )  =/=  0  -> 
( C `  ( F `  ( R `  k ) ) )  <  ( C `  ( R `  k ) ) ) )
33 peano2nn0 10848 . . . . . . 7  |-  ( k  e.  NN0  ->  ( k  +  1 )  e. 
NN0 )
34 fvco3 5951 . . . . . . 7  |-  ( ( R : NN0 --> S  /\  ( k  +  1 )  e.  NN0 )  ->  ( ( C  o.  R ) `  (
k  +  1 ) )  =  ( C `
 ( R `  ( k  +  1 ) ) ) )
357, 33, 34syl2an 477 . . . . . 6  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( C  o.  R ) `  (
k  +  1 ) )  =  ( C `
 ( R `  ( k  +  1 ) ) ) )
361, 2, 3, 4, 6algrp1 14079 . . . . . . 7  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( R `  (
k  +  1 ) )  =  ( F `
 ( R `  k ) ) )
3736fveq2d 5876 . . . . . 6  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( C `  ( R `  ( k  +  1 ) ) )  =  ( C `
 ( F `  ( R `  k ) ) ) )
3835, 37eqtrd 2508 . . . . 5  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( C  o.  R ) `  (
k  +  1 ) )  =  ( C `
 ( F `  ( R `  k ) ) ) )
3938neeq1d 2744 . . . 4  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( ( C  o.  R ) `  ( k  +  1 ) )  =/=  0  <->  ( C `  ( F `
 ( R `  k ) ) )  =/=  0 ) )
40 fvco3 5951 . . . . . 6  |-  ( ( R : NN0 --> S  /\  k  e.  NN0 )  -> 
( ( C  o.  R ) `  k
)  =  ( C `
 ( R `  k ) ) )
417, 40sylan 471 . . . . 5  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( C  o.  R ) `  k
)  =  ( C `
 ( R `  k ) ) )
4238, 41breq12d 4466 . . . 4  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( ( C  o.  R ) `  ( k  +  1 ) )  <  (
( C  o.  R
) `  k )  <->  ( C `  ( F `
 ( R `  k ) ) )  <  ( C `  ( R `  k ) ) ) )
4332, 39, 423imtr4d 268 . . 3  |-  ( ( A  e.  S  /\  k  e.  NN0 )  -> 
( ( ( C  o.  R ) `  ( k  +  1 ) )  =/=  0  ->  ( ( C  o.  R ) `  (
k  +  1 ) )  <  ( ( C  o.  R ) `
 k ) ) )
4415, 22, 43nn0seqcvgd 14075 . 2  |-  ( A  e.  S  ->  (
( C  o.  R
) `  N )  =  0 )
4513, 44eqtr3d 2510 1  |-  ( A  e.  S  ->  ( C `  ( R `  N ) )  =  0 )
Colors of variables: wff setvar class
Syntax hints:    -> wi 4    /\ wa 369    = wceq 1379    e. wcel 1767    =/= wne 2662   {csn 4033   class class class wbr 4453    X. cxp 5003    o. ccom 5009   -->wf 5590   ` cfv 5594  (class class class)co 6295   1stc1st 6793   0cc0 9504   1c1 9505    + caddc 9507    < clt 9640   NN0cn0 10807    seqcseq 12087
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1601  ax-4 1612  ax-5 1680  ax-6 1719  ax-7 1739  ax-8 1769  ax-9 1771  ax-10 1786  ax-11 1791  ax-12 1803  ax-13 1968  ax-ext 2445  ax-sep 4574  ax-nul 4582  ax-pow 4631  ax-pr 4692  ax-un 6587  ax-cnex 9560  ax-resscn 9561  ax-1cn 9562  ax-icn 9563  ax-addcl 9564  ax-addrcl 9565  ax-mulcl 9566  ax-mulrcl 9567  ax-mulcom 9568  ax-addass 9569  ax-mulass 9570  ax-distr 9571  ax-i2m1 9572  ax-1ne0 9573  ax-1rid 9574  ax-rnegex 9575  ax-rrecex 9576  ax-cnre 9577  ax-pre-lttri 9578  ax-pre-lttrn 9579  ax-pre-ltadd 9580  ax-pre-mulgt0 9581
This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-3or 974  df-3an 975  df-tru 1382  df-ex 1597  df-nf 1600  df-sb 1712  df-eu 2279  df-mo 2280  df-clab 2453  df-cleq 2459  df-clel 2462  df-nfc 2617  df-ne 2664  df-nel 2665  df-ral 2822  df-rex 2823  df-reu 2824  df-rab 2826  df-v 3120  df-sbc 3337  df-csb 3441  df-dif 3484  df-un 3486  df-in 3488  df-ss 3495  df-pss 3497  df-nul 3791  df-if 3946  df-pw 4018  df-sn 4034  df-pr 4036  df-tp 4038  df-op 4040  df-uni 4252  df-iun 4333  df-br 4454  df-opab 4512  df-mpt 4513  df-tr 4547  df-eprel 4797  df-id 4801  df-po 4806  df-so 4807  df-fr 4844  df-we 4846  df-ord 4887  df-on 4888  df-lim 4889  df-suc 4890  df-xp 5011  df-rel 5012  df-cnv 5013  df-co 5014  df-dm 5015  df-rn 5016  df-res 5017  df-ima 5018  df-iota 5557  df-fun 5596  df-fn 5597  df-f 5598  df-f1 5599  df-fo 5600  df-f1o 5601  df-fv 5602  df-riota 6256  df-ov 6298  df-oprab 6299  df-mpt2 6300  df-om 6696  df-1st 6795  df-2nd 6796  df-recs 7054  df-rdg 7088  df-er 7323  df-en 7529  df-dom 7530  df-sdom 7531  df-pnf 9642  df-mnf 9643  df-xr 9644  df-ltxr 9645  df-le 9646  df-sub 9819  df-neg 9820  df-nn 10549  df-n0 10808  df-z 10877  df-uz 11095  df-fz 11685  df-seq 12088
This theorem is referenced by:  algcvga  14084
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