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60 lines
1.5 KiB
60 lines
1.5 KiB
// COIN FLIPPING PROTOCOL FOR POLYNOMIAL RANDOMIZED CONSENSUS [AH90]
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// gxn/dxp 20/11/00
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mdp
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// constants
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const int N=2;
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const int K;
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const int range = 2*(K+1)*N;
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const int counter_init = (K+1)*N;
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const int left = N;
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const int right = 2*(K+1)*N - N;
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// shared coin
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global counter : [0..range] init counter_init;
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module process1
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// program counter
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pc1 : [0..3];
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// 0 - flip
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// 1 - write
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// 2 - check
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// 3 - finished
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// local coin
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coin1 : [0..1];
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// flip coin
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[] (pc1=0) -> 0.5 : (coin1'=0) & (pc1'=1) + 0.5 : (coin1'=1) & (pc1'=1);
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// write tails -1 (reset coin to add regularity)
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[] (pc1=1) & (coin1=0) & (counter>0) -> 1 : (counter'=counter-1) & (pc1'=2) & (coin1'=0);
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// write heads +1 (reset coin to add regularity)
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[] (pc1=1) & (coin1=1) & (counter<range) -> 1 : (counter'=counter+1) & (pc1'=2) & (coin1'=0);
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// check
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// decide tails
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[] (pc1=2) & (counter<=left) -> 1 : (pc1'=3) & (coin1'=0);
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// decide heads
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[] (pc1=2) & (counter>=right) -> 1 : (pc1'=3) & (coin1'=1);
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// flip again
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[] (pc1=2) & (counter>left) & (counter<right) -> 1 : (pc1'=0);
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// loop (all loop together when done)
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[done] (pc1=3) -> 1 : (pc1'=3);
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endmodule
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// construct remaining processes through renaming
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module process2 = process1[pc1=pc2,coin1=coin2] endmodule
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// labels
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label "finished" = pc1=3 & pc2=3 ;
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label "all_coins_equal_0" = coin1=0 & coin2=0 ;
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label "all_coins_equal_1" = coin1=1 & coin2=1 ;
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label "agree" = coin1=coin2 ;
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// rewards
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rewards "steps"
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true : 1;
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endrewards
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