... continued
We get the first elimination not due to the tridagon:
EL14c19-OR3-whip[3]: OR3{{n1r8c3 n1r4c3 | n7r6c1}} - r8n7{c1 c2} - c2n1{r8 .} ==> r3c3≠1Entering_level_L4_with_<Fact-10849>
Trid-OR2-ctr-whip[4]: c4n3{r3 r6} - c4n4{r6 r1} - c4n7{r1 r5} - OR2{{n3r6c5 n7r5c6 | .}} ==> r3c4≠9
Trid-OR2-ctr-whip[4]: c4n3{r3 r6} - c4n4{r6 r1} - c4n7{r1 r5} - OR2{{n3r6c5 n7r5c6 | .}} ==> r3c4≠2
Trid-OR2-ctr-whip[4]: c4n3{r3 r6} - c4n4{r6 r1} - c4n7{r1 r5} - OR2{{n3r6c5 n7r5c6 | .}} ==> r3c4≠1
EL13c290-OR4-whip[4]: c2n7{r8 r5} - r5n3{c2 c1} - OR4{{n3r9c1 n7r5c6 n7r6c1 | n5r7c1}} - r7c2{n5 .} ==> r8c2≠9
EL14c19-OR4-whip[4]: c2n1{r2 r8} - c2n7{r8 r5} - OR4{{n7r5c6 n1r8c3 n7r6c1 | n5r5c3}} - r3c3{n5 .} ==> r2c2≠9biv-chain[3]: r3n1{c9 c1} - r2c2{n1 n5} - r3c3{n5 n9} ==> r3c9≠9
z-chain[3]: r2n9{c6 c7} - c7n5{r2 r3} - r3c3{n5 .} ==> r3c6≠9, r3c5≠9
biv-chain[4]: c7n7{r1 r3} - b3n5{r3c7 r2c7} - r2c2{n5 n1} - b2n1{r2c4 r1c4} ==> r1c4≠7
z-chain[3]: c4n7{r6 r3} - c4n3{r3 r6} - r6n4{c4 .} ==> r6c6≠7
Trid-OR2-ctr-whip[3]: c4n3{r3 r6} - c4n7{r6 r5} - OR2{{n7r5c6 n3r6c5 | .}} ==> r3c4≠4
biv-chain[4]: r3c5{n2 n3} - c4n3{r3 r6} - c4n4{r6 r1} - b2n1{r1c4 r2c4} ==> r2c4≠2
biv-chain[4]: r3c5{n2 n3} - c4n3{r3 r6} - c4n4{r6 r1} - b3n4{r1c8 r3c8} ==> r3c8≠2
finned-x-wing-in-columns: n2{c8 c4}{r7 r5} ==> r5c6≠2
z-chain[4]: r3c4{n7 n3} - r3c5{n3 n2} - b3n2{r3c9 r2c7} - c7n5{r2 .} ==> r3c7≠7
hidden-single-in-a-block ==> r1c7=7
biv-chain[3]: b2n7{r3c6 r3c4} - c4n3{r3 r6} - c4n4{r6 r1} ==> r3c6≠4
hidden-single-in-a-row ==> r3c8=4
biv-chain[4]: c2n1{r2 r8} - c2n7{r8 r5} - c6n7{r5 r3} - r3n6{c6 c1} ==> r3c1≠1
hidden-single-in-a-row ==> r3c9=1
whip[1]: b3n2{r3c7 .} ==> r4c7≠2, r9c7≠2
naked-pairs-in-a-column: c7{r4 r9}{n8 n9} ==> r3c7≠9, r2c7≠9, r2c7≠8
whip[1]: r2n8{c6 .} ==> r1c4≠8, r1c6≠8
whip[1]: r2n9{c6 .} ==> r1c4≠9, r1c6≠9
whip[1]: b3n9{r1c9 .} ==> r1c1≠9
finned-x-wing-in-columns: n2{c9 c3}{r8 r6} ==> r6c1≠2
biv-chain[4]: r1c6{n6 n4} - b5n4{r6c6 r6c4} - c4n3{r6 r3} - r3n7{c4 c6} ==> r3c6≠6
stte
The use of two Imp630 patterns has allowed to reduce the maximum length of chains from 6 to 4.
Remark: if my purpose was to publish the resolution path, I would now restart all the computations with only tridagons, EL14c19 and EL13c290 activated in order to eliminate all the useless patterns. (*)
But my purpose here was to show that many instances of some impossible pattern can appear. It doesn't happen for the tridagon in this puzzle but the same happens for the tridagon in other puzzles.
(*) Indeed, I would first observe that EL13c290 belongs to the Select1 subset of Imp630 and EL14c19 to the Select3 subset. So I would first try with Select1 alone. I would then observe that chains of length 5 are needed and only then would I try with Select3 activated.
Additional remark: In [UMNR] (
https://www.researchgate.net/publication/372364607_User_Manual_and_Research_Notebooks_for_CSP-Rules), I've studied the 630 impossible patterns only wrt T&E(3) puzzles. But they can obviously also appear and be useful in T&E(2) or T&E(1) puzzles.
.