Identity

As almost all of the chess reporting is about top-performances, we sometimes forget that chess is also done recreational. For 99% of the chessplayers the efforts spent to become master aren't fully understood or even appreciated. This was unfortunately shown last week in some harsh reactions on a message of Oscar in which Oscar only mentioned that our new grandmaster Tanguy Ringoir had to pay 330 euro himself to get the title. A more explicit example of this apathy was demonstrated last interclubround in Oude God Mortsel when several players were drinking beer while playing. So I am very well aware that only few players are seriously/ fanatically playing chess as I do.

In my last article I talked about a scientific method to optimize openingchoices but in practice we see that many amateurs are already satisfied if they simply survive the openingphase. Tuning a repertoire is something many don't bother about. However to avoid frequent openingdisasters often players choose for a well-defined collection of side-systems. Some play the same systems for many years or decades, becoming dangerous opponents even for experienced players. The openingrepertoire becomes a part of the identity of the player. This immediately reminds me of Leo Boeye, opening each game with Nh3/Nh6 so always putting his mark.

If you are an amateur only playing locally then it is fully acceptable to ignore openingtheory. However once games of you are stored in databases and you are playing against more serious opponents then it is much harder to stick to this strategy. I guess once your rating surpasses 2200 see the list of force, it is time to adapt. I remember that once I lost a game against a grandmaster and 2 rounds later I got the same line again on the board by a 2300 player. I also lost that game despite better resistance. By the way here we also see the danger of blindly trusting statistics. Somebody finds a weak spot in your repertoire and there are immediately other players ready to use this discovery. In such situation you can't wait for the statistics as otherwise you risk to lose a long string of games.

Now and then it happens that I have to replace a piece of my repertoire which I played for many years. I never surrender easily a variation as that wouldn't be very consistent with the scientific approach I apply in my games. However I do admit that I many times wondered if it makes not more sense to ditch the Dutch in which I spent countless hours to repair lines and instead study some more solid openings. I don't find it easy to say goodbye to an opening at which you spent so much time and energy.

Nevertheless when I am convinced an opening is beyond salvation then it immediately and forever disappears from my repertoire. More precisely I only keep the variation in blitz/ rapid. Competitive players (see playing on the man) will surely find this an excessive decision but I consider it a logical step of my approach to the game. Some earlier examples of such changes were covered already on this blog: see Dutch steps in the English opening or the fake truth. In this article I want to show a extreme switch of repertoire which I recently did.

Maybe some loyal readers will still remember my article Gligorics concept against the Spanish exchange-variation. In that article I described how I started to play the system in 1998 and got over the years very experienced with it but had still some doubts about the correctness surely compared with the much more popular c5. My suspicion became reality when I recently discovered during a game-preparation with houdini and stockfish that a problem exists.

[Event "Analysis Gligoric-variation"] [Date "2014"] [White "?"] [Black "?"] [Result "*"] [ECO "C69"] [PlyCount "26"] 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6 5. O-O f6 6. d4 exd4 7. Nxd4 Bd6 { (Between 1997 and 2009 I played this move 11 times in standard-games and once in correspondence. It always hurts a bit if I have to drop an opening which I have played so long.)} 8. Qh5 g6 9. Qf3 h5 10. Qc3 {(I encountered already Qd3, h4 and Nc3 but never this weird move. In the database you can only find 1 example. Nonetheless it is exactly because of this move that I stop playing this opening.)} h4 $5 {(Last couple of days I spent quite some time to repair with this move the opening but to no avail. I think it is blacks best chance to defend.)} (10... Bd7 $5 11. Qb3 $1 (11. Nd2 $6 Qe7 12. Nc4 Bb4 $146 {(A clear improvement on the only game which continued with c5. I already discovered the move in 2009 and evaluated the move as playable.)} ) 11... b6 12. Re1 $1 $14 {(In 2009 I only looked at Qd3 but this is definitely superior.)}) 11. Nd2 {(Na3 is slightly less clear even though black surely has no easy equality.)} h3 12. g3 Nh6 13. Nc4 Nf7 $14 { (The most simple is to eliminate the pair of bishops with Nxd6 but also Bf4 looks an interesting option to play for a win.)} *

I didn't find a solution during the game-preparation so in the end I chose to experiment with something new. A deeper analysis of the specific problematic line was planned for after the game.

[Event "Interclub Hoboken - Deurne"] [Date "2014"] [White "Cools, G."] [Black "Brabo"] [Result "1-0"] [ECO "C69"] [WhiteElo "2260"] [BlackElo "2337"] [PlyCount "163"] 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6 5. O-O f6 6. d4 exd4 7. Nxd4 c5 { (It is the first time that I play the mainline as I recently discovered a problem in my favorite Gligoric system which I could not fully solve. I guess the chance is very small that Gorik was aware about it but scientifically I found it inappropriate to continue playing an inferior line.)} 8. Ne2 Qxd1 9. Rxd1 Bd7 10. Be3 O-O-O 11. Nbc3 Re8 12. Rd2 Bc6 13. Rad1 b6 14. f3 Ne7 15. Nf4 Ng6 16. Nh5 Rg8 $5 {(Here my preparation ended. I still remembered that Stockfish recommends this move and judges the position as equal but nothing more. Today after deeper analysis I rather prefer Ne5 and especially f5 which creates a more attractive type of position which does not mean that it is really better.)} (16... Ne5 $5 17. b3 c4 18. Nd5 a5 19. Kf2 Kb7 $13) (16... f5 $5 17. exf5 $5 Nh4 18. Bf4 Nxf5 19. Nd5 Nd4 20. Nxc7 Re7 21. Nxa6 {(The correspondence-game Hoffmann Frank - Shnyrev Viktor Petrovich played in 2011, ends here in my database with a draw. I think the position is sufficiently interesting to continue playing with black in standard-chess.)}) 17. Kf2 Be7 {(I prepare g6 but the plan is rather long-winded.)} 18. Nd5 Bd8 19. g4 Ne5 20. b3 Ref8 21. h3 g6 22. Ng3 Re8 23. f4 Nf7 24. f5 Bxd5 25. Rxd5 Be7 26. Bf4 Rd8 $5 {(I could not calculate the complications in a few minutes so I chose in the end for the safe but passive Rd8.)} (26... Bd6 $5 27. Bxd6 Nxd6 28. Rxd6 {(It was this exchange-sacrifice which worried me in the game.)} cxd6 29. Rxd6 Rd8 30. Rxb6 (30. Rc6 Kb7 31. Rxf6 Rd2 32. Kf3 Rxc2 33. Rf7 Kc6 34. Rxh7 Rc3 35. Kf2 Rc2 36. Ke3 Rc3 37. Kf2 Rc2 38. Ke3 Rc3 39. Kf2 $11) 30... Rd2 31. Ke3 $1 Rxc2 32. Rxa6 Kb7 33. Rxf6 Rc3 34. Kf2 Ra8 35. a4 Rxb3 $5 {(C4 is a serious alternative but the position stays balanced if I look at the evaluations of the engines.)} 36. Rf7 Kc6 37. Rxh7 $13) 27. Rxd8 Bxd8 28. Ne2 $5 {(Putting the bishop on the long diagonal via d2 must be considered with a not pleasant position for black.)} Be7 29. Nc3 Re8 $6 {(More accurate is c6.)} 30. Nd5 $6 { (Immediately after the game Gorik rightfully admitted this was not optimal. Correct was h4 to use the advantage of the flexible pawn-majority on the kingside. Because blacks rook is not anymore on the g-file, white can now answer gxf5 with exf5.)} Bd8 31. Re1 c6 32. Nc3 b5 33. Re2 Ba5 34. Nd1 Rd8 35. Nb2 Bc3 36. Nd3 c4 37. bxc4 bxc4 38. Nc5 Rd1 39. Ne6 Ra1 $6 { (Black is back in the game thanks to whites mistake on move 30 but now needs to slow down which I forget in my rush. With the simple g5 I could easily stop the pawns on the kingside and white needs to force a draw by chasing blacks rook.)} 40. h4 Rh1 $6 { (I also understood by now that whites pawns run fast. Should I slow down the pawns or I anyway better take the a-pawn. These kind of critical decisions you do not want to take on move 40 with only a minute on the clock left but I had no choice. Of course I take the wrong decision as I only consider Kg3.)} (40... Rxa2 $1 41. Nf8 g5 42. hxg5 fxg5 43. Bg3 Ra5 44. Nxh7 Rb5 $14 {(The a-pawn is still far away from the promotion but white can not ignore it.)}) 41. Bg3 Ra1 $5 {(A doubtful decision to admit being wrong with my 40th move. The 2 tempos play an important role but I could not find anything clearly better.)} 42. Nf8 g5 43. Nxh7 gxh4 44. Bxh4 Ne5 $6 {(More stubborn was Bd4. With Ne5 I still have some tricks but Gorik does not make any blunders.)} (44... Bd4 $1 45. Kg3 Rg1 46. Kh3 Rh1 47. Rh2 Rg1 48. Bf2 Bxf2 49. Rxf2 Rh1 50. Rh2 Rg1 51. e5 fxe5 52. Kh4 e4 53. Nf6 Re1 54. Kg3 $16) 45. Nxf6 Bd4 46. Kg3 Rg1 47. Rg2 Rf1 48. Nh7 Bc3 49. Kh3 Rh1 50. Rh2 Rxh2 51. Kxh2 Nxg4 52. Kh3 Ne3 53. f6 Bxf6 54. Nxf6 Nxc2 55. e5 Nd4 56. Ne4 Kd7 {(My only hope is to get the feared bishop and knight endgame on the board but Gorik skilfully avoids it.)} 57. Kg4 Ke6 58. Bg3 Ne2 59. Nc5 Ke7 60. Bh4 Ke8 61. Kf3 Nc1 62. a3 Nb3 63. Nxa6 c3 64. Nb4 Nd4 65. Ke4 c5 66. Nd3 Nb3 67. Kd5 c2 68. Bg5 Kd7 69. e6 Ke8 70. Kc4 c1=Q 71. Bxc1 Ke7 72. Kxb3 Kxe6 73. Nxc5 {(The a-pawn remains on the board. I continued still a few more moves as we both had only a few minutes left.)} Kd6 74. Kb4 Kc6 75. a4 Kb6 76. a5 Ka7 77. Kb5 Ka8 78. Kb6 Kb8 79. a6 Ka8 80. Ne6 Kb8 81. Nc7 Kc8 82. a7 1-0

So I also didn't manage to repair the line later. This meant that the opening went to the waste-bin although I have a very strong suspicion that nobody knew about the problem. Nor in the big database nor in correspondence games you can find the critical line and white has to find some very typical difficult engine-moves. It is an extreme swap of opening but I don't want to wait till somebody does his homework and shows on the board what I already would know longtime.

Talking about extreme switches I shouldn't forget my opponent of the previous game,  Gorik Cools. In the database I found many games of him from 1989 till 2011 with the kingsgambit but in 2012 he exchanged the opening for the exchangevariation of the Spanish. One of his kingsgambit-games which didn't make it to the databases can be replayed below.

[Event "Hoboken - Deurne"] [Date "2009.09.27"] [Round "1.1"] [White "Cools, Gorik"] [Black "Sadkowski, Daniel"] [Result "1/2-1/2"] [ECO "C20"] [PlyCount "105"] 1. e4 e5 2. f4 exf4 3. Nf3 g5 4. Bc4 Bg7 5. O-O d6 6. d4 Nc6 7. c3 h6 8. Qa4 Bd7 9. Qb3 Na5 10. Bxf7 Kf8 11. Qa3 Kxf7 12. Qxa5 Ne7 13. g3 Nc6 14. Qd5 Be6 15. Qb5 Bh3 16. Rf2 Qd7 17. gxf4 gxf4 18. Bxf4 Kg8 19. Nbd2 Rf8 20. Bg3 Rh7 21. Re1 Bh8 22. Qc4 Rhf7 23. Nh4 Ne7 24. Rxf7 Rxf7 25. Ng2 c6 26. Rf1 d5 27. exd5 Nxd5 28. Rxf7 Qxf7 29. Nf4 Bf5 30. Nxd5 cxd5 31. Qc7 Qxc7 32. Bxc7 Bf6 33. Bf4 h5 34. Kf2 Kf7 35. Ke3 Ke6 36. a3 b5 37. Bh6 a5 38. Nb3 a4 39. Nc5 Kf7 40. Nd3 Kg6 41. Bf4 Kf7 42. Nb4 Be6 43. Na6 Bd7 44. Nc5 Bc8 45. Kf3 Kg6 46. Nd3 Kf5 47. Bh6 Be6 48. Nf4 Bf7 49. Ng2 Be7 50. Bf4 Ke6 51. Be3 Bd6 52. h4 Bg6 53. Nf4 1/2-1/2

The type of position in the exchange-variation of the Spanish is totally different from the tactical positions of the kingsgambit. Yet I do believe Gorik made the right decision to make this switch. With the ever stronger playing engines it becomes harder and harder to play successfully gambits on the long term. Besides it is also more difficult to show the same tactical alertness than we were 20 years younger. By the way I read that the writer of the recently published book on the Kingsgambit, John Shaw made exactly the same switch in his repertoire. It looks indeed sensible to realize that we stay not forever young and our identity slowly evolves over the years.

Brabo

Openingchoices

In my article creating a repertoire I described my methods of refining and enlarging my openingknowledge of my repertoire. However to built up a repertoire from scratch is for a novice something very difficult. Which opening should I pick up first and what matches with my style? Any opening can be learned but I do understand that many players don't know where to start with the abundance of possibilities. On the internet as in the club people often ask my advise. Should I play e4, d4 or still something else with white? Should I answer 1.e4 with the Sicilian or French.. and which variation?

Except a rare case, I normally refuse to help. I have a very narrow repertoire so there are surely players better qualified that myself, able to compare better openingchoices. It also makes little sense to define somebodies repertoire if you don't know well the player. Besides many novices don't have a clue about what chess is about and what exactly can be expected.

Therefore it is important as novice to try and taste many openings. I remember that I started with 1.d4. Some readers maybe still remember my article gambits in which I stated that I played hundreds maybe thousands of games against computers. From experience I learned that 1.d4 gives better chances to hold out against computers than 1.e4. Today we all know that 1.d4 leads to a closed game so is more efficient against computers but those basic rules I only heard many years later. I only switched to 1.e4 when big blunders became more rare and I started to play more often against humans.

So our openingchoices are heavily influenced by external elements. I still remember that in my first tournament (1993) I wasn't satisfied about my openingchoice 1.d4 and in that time I just acquired the book Dr. Max Euwe Praktische schaaklessen deel 3.

The book is probably sold out but a player starting with competitive chess doesn't need anything extra. Of course the latest developments aren't covered but the didactic style is very comprehensible and I've consulted regularly the book still many years later. It was this book which let me discover the Dutch defense as an acceptable answer on 1.d4.

Computers, books have a big influence on our openingchoices but also the openings which other players choose. It is no coincidence that in some (smaller) clubs, half of the players have a similar repertoire. The best player of the club is successful with a specific repertoire and the other players try to copy this to improve their chances. It is pretty logical to play an opening which you can't refute yourself.

In fact our repertoire is a product of coincidences and emotions. Some more ambitious players aren't satisfied by this. Wouldn't it be better to build a repertoire in a more scientific way? In my first years I created a mathematical model based on piece-activity to define which openings are good and which are less good. The more extra possibilities you had compared with the opponent, the better the openingchoice. In the initial position white has 16 pawnmoves and 4 knightmoves so 20 in total. 1.e4 is the move which increases maximally the possibilities to 30: 15 pawnmoves, 5 knightmoves, 5 bishopmoves, 4 queenmoves and 1 kingmove.

Obviously an absurd method as quantity says very little about quality. On the other hand I learned from this the fundamental principles of occupying the center and strive for activity so it wasn't all useless. A very similar but more complex mathematical model was recently published on Chessbase in which conclusions were made based on square utilization and occupancy. The power of a modern computer was used to process thousands of games. However the same remark is also valid here that such numbers can't be converted to concrete moves. An apparently small detail can chance the complete picture of a position.

So is there really nothing which we can use to make in a scientific way a proper openingchoice? Yes there is as we have today engine openingbooks which show statistics of the performances for each opening in practice, see my article green moves. We also have the Chessbase reports which can be queried per player. Not only you get a view about what a player has played before but also how well the player scored in an opening. Although there are serious limitations as Kara rightly remarked in a reaction on my previous article. Such report often shows a distorted picture for amateurs because it mainly includes the games against stronger professional players. Of my 720 standardgames only 255 games can be found in the Big database 2015 and you can only find 1 partial one of my 20 correspondence games in the databases. Besides it is often not really better to choose a variation in which the opponent lost before. If the opponent repeats the line then you can be almost sure that he prepared an improvement. Often it is more interesting to choose a variation in which the opponent scores well or in which he has recently won a game on the condition that you have a fresh idea prepared.

Another angel to optimize openingchoices is to start from the own qualities instead of the opponents. A coach can surely help but even without a coach a lot is possible. If you already play chess for some years and you archive the games properly then you can make an openingbook of it which is much more accurate than a Chessbase report from the Big database 2015. If you play many lines by both colors (see article swapping colors) then it makes sense to create a separate openingbook for white and black. I demonstrate the possibilities of this scientific method with an example of my white openingbook after the first move 1.e4.

You always have to be very careful with statistics as very often wrong conclusions are made. First we need to check if there are sufficient data points to absorb statistical fluctuations. In the article to study chessopenings I indicated that the influence of openings is rather limited to the final result of the game. 10 games is the absolute minimum to tell something meaningful but preferably we have many times more. We also need to take into account the opposition. Instead of looking to percentages it is more interesting to look to the TPR achieved.

In the example we see some remarkable differences in TPR between the different black answers on my first move which can't be just explained by statistical noise. Some openings really fit me better than others. We see that my opponents with the Scandinavian defense (d5) averagely underachieve with 200 points (2000-1790). However with the Caro-Kann (c6) my opponents perform averagely 100 points more than expected (2011-2132) so there I lose rating. This info shows clearly where a repertoire should be adapted or improved.

The same process can be repeated for positions deeper in some openings. The repertoire is built by openings which statistically result in superior performances. Players with a broad repertoire can extract an extra advantage from this method by also applying it during a game-preparation. Suppose your opponent plays against 1.d4 a line in which you score slightly negatively but against 1.e4 he chooses a line in which your report shows a +100 TPR for you then of course you start the game with 1.e4.

Now I surely don't claim that with this scientific method always a perfect openingchoice will be made. Sometimes you are in the mood to play something more creative or a draw is more than sufficient. Playing an opening in which you don't score well, can also be educative. Besides a score doesn't have to stay forever negative as below screenshot from my Caro Kann games demonstrates.

Despite the negative TPR of 100 points we discover that I won my last 9 games although against modest opposition. Some study can influence a performance positively. Therefore it is often better to prepare statistics from only the more recent games again at the condition there is sufficient data.

Playing and trying a lot is fundamental to get an acceptable return by this method. The last few years I couldn't play much due to the combination of work-family so I just muddled around. Small adjustments to my repertoire are regularly made but I don't experiment with completely new openings. Pragmatism or fear, something which is open for debate.

Brabo

Exchange sacrifices

Most clubplayers have sacrificed material in some games to launch an attack. However sacrificing purely for strategical or positional grounds is something which I almost exclusively see in games of more advanced players. Less experienced players don't grasp yet the abstractness of activity, strong squares or weaknesses. Obviously you only sacrifice material if you understand the value which you get in return.

In this category of sacrifices there is often used the exchange sacrifice. A player sacrifices the rook for bishop or knight. For most topplayers this is something very common but when I look in my personal database of standard games, I have to admit that it is rather rare in my practice. My non-attacking style (see gambits) doesn't explain everything as a game is always played by 2.

One of the very first times that I encountered an exchange sacrifice on the board, was in the Open Gent 2000 by the Belgian grandmaster Vladimir Chuchelov  (today not anymore an active player but a trainer of among others the number 2 of the world Fabiano Caruana)

[Event "Open Gent 4de ronde"] [Date "2000"] [White "Chuchelov, V."] [Black "Brabo"] [Result "1-0"] [ECO "A90"] [WhiteElo "2540"] [BlackElo "2265"] [SetUp "1"] [FEN "4b3/rp4r1/p1pn1k2/3pN2p/PP1P1Pp1/2KBP1P1/7R/7R w - - 0 42"] [PlyCount "7"] {(The remainders of the stonewall are taken down by a simple exchange sacrifice. )} 42. Rxh5 $1 Bxh5 43. Rxh5 a5 $2 {(A misplaced try to find activity.)} 44. Rh6 Ke7 45. f5 {(With a handful of seconds on the clock I had seen enough. Whites attack anyway crashes through.)} 1-0

A simple but efficient example of how quickly a defense can collapse after an exchange-sacrifice. Much more creative was my exchange-sacrifice in 2002 against Raf De Coninck.

[Event "H.V. Alcatel - Agfa Gevaert"] [Date "2002"] [White "Brabo"] [Black "De Coninck, R."] [Result "*"] [ECO "C78"] [WhiteElo "2284"] [BlackElo "2156"] [SetUp "1"] [FEN "3r3r/2kn1p2/p1nb3p/P1p1p1p1/1pP1P3/1N2BN2/1P3PPP/3RR1K1 w - - 0 25"] [PlyCount "13"] 25. Rd5 $5 Nf6 $2 {(Black takes the bait and gets into problems hereby. Better was to complete the development with e.g. Rhe8 and black is at least equal.)} (25... Rhe8 26. g4 Nd4 (26... Nf6 27. Bxc5 Nxd5 28. cxd5 Bxc5 29. Nxc5 Nxa5 30. Nxa6 Kd6 31. Nd2 $44) 27. Bxd4 exd4 28. e5 Bf8 29. Kg2 Re6 30. h4 gxh4 31. Nxh4 $13) 26. Bxc5 $1 Nxd5 27. cxd5 Bxc5 28. Nxc5 Nxa5 29. Nxe5 Rhe8 30. Ncd3 f5 31. f3 $14 {(Whites center dominates clearly over the exchange.)} *

Of course black should've refused the exchange but understood too late how large the compensation is. Sometimes sacrificing an exchange isn't fully objectively correct but it is an ideal practical tool to change the character/ course of a game. Such speculative/ practical sacrifice was played by Wouter Gryson in our mutual game. The complete game was earlier covered in the article the fake truth.

[Event "Interclub Deurne - KBSK"] [Date "2012"] [White "Brabo"] [Black "Gryson, W."] [Result "*"] [ECO "B06"] [WhiteElo "2334"] [BlackElo "2260"] [SetUp "1"] [FEN "r4rk1/2p2pbp/1q1ppnp1/N4b2/PPPP4/2BN1Q2/5PPP/R3R1K1 b - - 0 21"] [PlyCount "17"] 21... Rxa5 $6 {(A speculative exchange-sacrifice which was mainly justified by whites earlier large time-consumption. Objectively c6 is more correct but of course it is not a nice choice and it is doubtful if it generates better practical chances.)} 22. bxa5 Qb3 23. Rac1 Qxc4 24. Nb2 $6 { (More accurate is Nb4 and the extra material is probably sufficient for white if his technique does not fail)} Qb3 25. Qd1 $6 {(Surrendering the diagonal a8-h1 is not the best choice. Nd1, recommended by the engines is clearly superior. )} Qb7 26. Nc4 Nd5 27. Ne3 Nf4 28. d5 Bxc3 29. Rxc3 Be4 {(Black has managed to find a lot of counterplay for the exchange.)} *

The previous examples are clear but it is often much less evident. Last I had to decide to permit or not an exchange-sacrifice in my game against the Belgian FM Gorik Cools. In the end I chose to avoid the possibility but ended up in a dangerous position.

[Event "Interclub Hoboken - Deurne"] [Date "2014"] [White "Cools, G."] [Black "Brabo"] [Result "*"] [ECO "C69"] [WhiteElo "2260"] [BlackElo "2337"] [SetUp "1"] [FEN "2k1r1r1/2p1bn1p/pp3pp1/2pR1P2/4PBP1/1P4NP/P1P2K2/3R4 b - - 0 26"] [PlyCount "22"] 26... Bd6 $5 {(Objectively the best move but then you should not be afraid of the complications hereafter.)} (26... Rd8 $5 {(I was not able to calculate in a few minutes the complications after Bd6 so I chose for the prudent but passive Rd8.)}) 27. Bxd6 Nxd6 28. Rxd6 {(It was this exchange-sacrifice which worried me during the game.)} cxd6 29. Rxd6 Rd8 30. Rxb6 (30. Rc6 Kb7 31. Rxf6 Rd2 32. Kf3 Rxc2 33. Rf7 Kc6 34. Rxh7 Rc3 35. Kf2 Rc2 36. Ke3 Rc3 37. Kf2 Rc2 38. Ke3 Rc3 39. Kf2 $11) 30... Rd2 31. Ke3 $1 Rxc2 32. Rxa6 Kb7 33. Rxf6 Rc3 34. Kf2 Ra8 35. a4 Rxb3 $5 {(C4 is a serious alternative but the position stays approximately balanced if I trust the evaluation of the engines.)} 36. Rf7 Kc6 37. Rxh7 $13 *

So the exchange-sacrifice was surely playable but not winning. It is an open question what would've happened if I permitted the complications. Such reluctance exists much less with top-players. Still it was a big surprise in the previous worldchampionship that Anand dared to sacrifice the exchange in his last black-game especially as there were perfectly acceptable alternatives.

[Event "Carlsen-Anand World Championship"] [Site "Sochi RUS"] [Date "2014.11.23"] [Round "11"] [White "Magnus Carlsen"] [Black "Viswanathan Anand"] [Result "1-0"] [ECO "C67"] [SetUp "1"] [FEN "rr3b2/2p2p2/2k1bNnp/p1pNP1p1/P1P1K1P1/2B4P/5P2/3RR3 b - - 0 27"] [PlyCount "36"] 27... Rb4 {(Attractive but at the same time black goes all in. Carlsen shows with an impeccable technique that in this position the exchange is a bit more important.)} 28. Bxb4 cxb4 29. Nh5 Kb7 30. f4 gxf4 31. Nhxf4 Nxf4 32. Nxf4 Bxc4 33. Rd7 Ra6 34. Nd5 Rc6 35. Rxf7 Bc5 36. Rxc7 Rxc7 37. Nxc7 Kc6 38. Nb5 Bxb5 39. axb5 Kxb5 40. e6 b3 41. Kd3 Be7 42. h4 a4 43. g5 hxg5 44. hxg5 a3 45. Kc3 1-0
So exchange-sacrifices are certainly not always straight-forward. For defense and attack it is often a difficult balance. Personal taste, tournament-situation,... play an important role. However it stands firm that exchange sacrifices more or less guarantee creative positions and interesting complications. Did you play once such type of exchange-sacrifice (so not the famous sacrifice on c3 of the Dragon) and there was no direct tactical justification then write it down in a reaction !

Brabo