Article in the ICCF Bulletin back in 2004

In this article concerning the use of chess engines in modern CC play by Simon Hradecky, he wrote “Whenever you join discussions about correspondence chess, you will find arguments right away that chess engines have become so good these days that humans cannot win anymore against them.” And then he cited a challenge where CCGM and former world CC Champion Arno Nickel (with the help of computers) played correspondence games against six different engines and lost overall. Hradecky went on to explain, “I am convinced otherwise, and my own experience seems to support my conviction fully.”
       He added, “Computers... cannot deviate from their given procedures and knowledge....Did I just say, that chess engines are reliable, do not get caught in mindsets and do not make mistakes? Well, somehow I did, but that statement needs to be put into perspective: accuracy and reliability comes at a high price, namely performance. To compute a position at full accuracy, chess engines need to check all possible moves, all their countermoves and so on – so their ability to look ahead and see developments is vastly limited. To compensate for that, chess engines use different criteria to select the possible moves, which they analyse further, while they just do not follow up the other ones. Only that “trick” allows them to look as far ahead as they do today and to develop their current strength...engines, however, may overlook the stronger, perhaps winning moves amongst the remaining (ones, and) as a result, chess engines, too, get caught in "mindsets" and make mistakes, just like humans.”
       Hradecky went on to cite an example that occurred in the 8th World Championship game between Vladimir Kramnik and Peter Leko in Brissago/Switzerland 2004, Here is the position in question after Black’s 23...Re8-e2:

      When engines of the day computed the queen sacrifice by Kramnik  (move 24.Qxe2) they thought it was winning for Kramnik and they continued to show a winning advantage for White for more than 15 minutes.  It wasn’t until after Leko’s winning 25…Qd3!! that the engines started to doubt and reduce the score.

       Kramnik confirmed later in the press conference that this queen sacrifice was prepared and checked using chess engines during his preparation but he and his team misjudged the value of his passed P.  They also missed Leko’s subsequent sacrifices which were found OTB!
       I was curious to see how today’s engines compared so let Fire 1.5 xTreme w64 analyze this position for 10 minutes and its conclusion was 24.bxa6 Rxf2 25.Kxf2 was totally equal (0.00) but after actually playing the moves it took an additional 3 minutes to realize that Black is still winning. Fire eventually figured out that after 23…Re2 Black is winning, but it took about 20 minutes.
       Analysis with Houdini was a little different.  It’s initial evaluation was that 24.Qxe2 was about a 1/3 of a P in White’s favor but after 3-1/2 minutes it changed its mind and thought Black had an advantage of nearly 2P’s so switched its attention to 24.bxa6 which it considered nearly equal.  After another 3 minutes or so, it concluded that 24.bxa6 wasn’t any better (2P advantage for Black). 
       The actual game continued 24.Qxe2 Bxe2 25.bxa6 Qd3 Kramnik's preparation went this far, believing his passed pawn gave him compensation. But White is lost here thanks to the nice sacrificial lines that Leko found over the board. 26.Kf2 Bxf3 27.Nxf3 Ne4+ 28.Ke1 Nxc3 29.bxc3 Qxc3+ 30.Kf2 Qxa1 31.a7 h6 32.h4 g4 0-1.
       What this little experiment shows is that engines (and computers) of today are much faster in arriving at their conclusions than those of yesteryear, but just as a reminder of what I said before, you absolutely must give them some time to ponder the position.  A minute or two, even 5 or 10 in a complicated position is just not sufficient.  Then, after all that, you have to step through the lines just to make sure nothing was missed. 
       It’s also been argued that engines have allowed weaker players to compete with stronger players and that the difference between ordinary CC masters and world champions depended only on who had the biggest, badest computers and the best software.  As Hradecky pointed out the gap between strong players using chess engines and the weak players using chess engines still remains because the difference in understanding and human skills of the stronger player will still win against the weaker player. Believe me, he's right about this.
       So what exactly have engines introduced into CC?  First is that you rarely see game losing blunders even in games by low-rated players.  What’s really changed is that CC players also need to know how to use chess engines to compliment their own skills.
       In recent years I’ve discovered it is necessary, like it or not, to make an effort to learn how to incorporate engines into my CC play.  I’ve never been one for quantity over quality in CC.  I’d rather play 10-12 games as good as I can as opposed to slopping through 50 or a hundred and only spending a few seconds per move.  The funny thing is engines haven’t made selecting moves any easier as I have discovered I am spending just as much time going over engine analysis and trying out different ideas of my own as I used to back in the old post card days.  In fact, in some ways it’s worse because in addition to my own thoughts on the position (usually pretty crappy) I have to look at engine lines and because “they” recommend using more than one engine, that can often mean two or three different moves that are “best” depending on which engine you are using. When that happens you have to agonize over which engine to believe and that still means making a judgment call based on one’s understanding of the position.