Why are computers so bad at chess puzzles?

So I stumbled across this puzzle which claimed white could achieve a mate in 74 moves. Oh my, I thought. Is this even possible? Well, challenge accepted. I tried and failed, but soon got the understanding of the pattern and finished the puzzle. It wasn't really that hard, most chess players would complete it. It all comes down to forcing/zugzwang black so that he/she doesn't have any choice but to dance to whites music.



Then I thought I'd try to feed this puzzle into my computer (8 core CPU @ 4.5 GHz) using the latest Stockfish engine (one of the strongest in the world). It turns out the engine/computer, even after calculating millions of half-moves, couldn't get it right. It thought a stalemate was the best thing white could achieve.



Why can't the computer calculate this easy puzzle?



Here's the puzzle:

My PC specs:

*8GB RAM

*8 core CPU @ 4.0 GHz

*AMD 7870 1 GHz 2 GB VRAM

*Windows 7

*Latest version of Stockfish (DD x64 SSE4.2)

How long did you let it think?

At Depth 35, Houdini 4 still gives a draw:

Mate in 74 would be about, what, 147 plies? Probably beyond the horizon for just about any engine, unless there are many forced moves.

A good player will solve this easily, although it may need more than 74 moves. An engine will solve it after several days.

Here's another example- a human can solve it in two minutes. It's mate in 16. Houdini solves this in less than five seconds, while Komodo and Stockfish will need quite some time (more than five minutes in my slow box) because they are pruning the second move.

I have it in 10?

EDIT: Of course I have to take the knight first. In which case I'll have to play h3.

In that position, if black lets the e1 knight out, isn't it all over?

Your expectation is unrealistic, computers are great and finding forced mate problems but they  can't go 148 ply deep and neither can anybody else. Claiming that means they are bad at solving problems is....just.....wrong. 

@scottrf: also black can play c4 instead moving the queen back to a1 which leaves the queen guarding the important square. the tempo that black gains there saves him because the white knight can never lose a tempo.

About an hour

First of all, its so easy that most people will understand it within a minute, unless you're lazy or a complete novice. Second of all, I already did show the solution. Press the lightbulb button.

@thayup white's first move clearly has to be capturing the knight. After that it is beyond me because I have tried both h3 and h4 with the idea of promoting to a knight and haven't been able to figure it out.

Thanks for the great answers. Here's another one. Mate in 290.