user17688: I have a PC, an AMD RYZEN 7 2700 with minimal graphic card and 8 GB RAM. It has 8 cores and 16 threads. 
If a chess engine is programmed well will it be able to calculate to a depth of 125  in 15 seconds? My question to the forum is is it scientifically possible? Please share your thoughts. 

user17713: To complement the answer by user1583209, I would point towards the supercomputer Sesse. In normal positions, I've never seen it even come close to reaching a depth of 125. A more typical depth reached from what I've seen would be something like 40, i.e. very far off from 125. In the case of a home PC (even with Ryzen 2700), you likely won't even come close to 40 within the allocated 15 seconds. Therefore, assuming that your engine is actually half-decent and isn't instantly pruning almost every single variation, I'd say 25 is much more realistic than 125.

user11629: Sure it could, if you do a lot of pruning and consider only one or few branches. However it would likely not be a very strong engine, because it would miss lots of relevant sidelines/variations.

Longer answer:
The "depth" you see in engines does not mean, that the engine calculates all variations to that depth. This would be practically impossible because of the huge number of variations: After just 1 white and 1 black move you  already have 20*20=400 different games. With every move that you look ahead this number increases by a factor that is on average around 35.
Because of that, engines are (just like humans) only considering what they think are the relevant lines, by ignoring all other moves. This is called "pruning".
If you do this pruning very heavily you can end up with an engine that can look very deep. However it would look in a very narrow range, considering only one line or so. 
It would miss lots of moves/lines and be very weak.  Roughly speaking you could say that engines are doing a compromise between depth, width (number of variations) and allocated time in order to optimize for playing strength.

17688: <p>I have a PC, an AMD RYZEN 7 2700 with minimal graphic card and 8 GB RAM. It has 8 cores and 16 threads. </p>

<p>If a chess engine is programmed well will it be able to calculate to a depth of 125  in 15 seconds? My question to the forum is is it scientifically possible? Please share your thoughts. </p>
 17713: <p>To complement the answer by user1583209, I would point towards the supercomputer <a href="http://analysis.sesse.net/" rel="nofollow noreferrer">Sesse</a>. In normal positions, I've never seen it even come close to reaching a depth of 125. A more typical depth reached from what I've seen would be something like 40, i.e. very far off from 125. In the case of a home PC (even with Ryzen 2700), you likely won't even come close to 40 within the allocated 15 seconds. Therefore, assuming that your engine is actually half-decent and isn't instantly pruning almost every single variation, I'd say 25 is much more realistic than 125.</p>
 11629: <p>Sure it could, if you do a lot of pruning and consider only one or few branches. However it would likely not be a very strong engine, because it would miss lots of relevant sidelines/variations.</p>

<hr>

<p>Longer answer:</p>

<p>The "depth" you see in engines does not mean, that the engine calculates all variations to that depth. This would be practically impossible because of the huge number of variations: After just 1 white and 1 black move you  already have 20*20=400 different games. With every move that you look ahead this number increases by a factor that is on average around 35.</p>

<p>Because of that, engines are (just like humans) only considering what they think are the relevant lines, by ignoring all other moves. This is called "pruning".</p>

<p>If you do this pruning very heavily you can end up with an engine that can look very deep. However it would look in a very narrow range, considering only one line or so. </p>

<p>It would miss lots of moves/lines and be very weak.  Roughly speaking you could say that engines are doing a compromise between depth, width (number of variations) and allocated time in order to optimize for playing strength.</p>
