Blockade

[Lyudmil Tsvetkov]

[D]1r1r4/3q2k1/3p1p2/p1pNpPp1/PpP1B1Pp/1P5P/2Q5/6K1 b 0 1

This is just a very simplistic example of an efficient blockade.
How do you assess this position? (and, please, do not tell me, that some engines would actually see black in advantage by some 5 full pawns)
And, please, note, that this is not an irregular, but a very realistic, very practical middlegame position.

[Lyudmil Tsvetkov]

Another example of blockade.

[D]8/4k3/n1p1b1p1/P1p1PpPp/1pPn1P1P/1P1P2K1/8/R2BR3 w 0 1

What do your engines think, is it a draw, or does black have an advantage score of some 6-7 full pawns?

I am sorry that sometimes blockade looks oversimplistic, like in the above position, but at least, it is a funny one, and you can not imagine what tricks, traps, etc. proud humans are capable of in the struggle for survivor against the engine monsters.
As the engines grow stronger, you have to adapt.

[Lyudmil Tsvetkov]

[D]8/2n5/1pPp2k1/1P1P1pPp/2B2P1P/6K1/1P6/8 w 0 1

Another simple one blocking/fortress position.
Should be recognized quite easily.

[lucasart]

[D]8/2n5/1pPp2k1/1P1P1pPp/2B2P1P/6K1/1P6/8 w 0 1

Another simple one blocking/fortress position.
Should be recognized quite easily.

Critter 1.6a evaluates this position at 0. The eval itself returns a zero score, without searching. There is some built-in detection of blockades.

However, it probably is limited to certain types of blockades. Richard would be better placed to explain the details. For example, Critter doesn't see the blockade in the other two positions you posted.

[Lyudmil Tsvetkov]

Congratulations to Critter!