Correct BS for SD-S17 and DD-S17 with Late Surrender?

I've just noticed that the BS charts on Michael Shackelford's and Ken Smith's websites disagree quite a bit on when it is appropriate to surrender, especially in SD games. For SD-S17 games, Shackelford says to surrender only in the following 3 situations: 16 v. 10, 16 v. Ace, and (7,7) v. 10. Smith says that you should also surrender on 16 v. 9 and 15 v. 10, and that you should stand (not surrender) on (7,7) v. 10. For DD-S17 games, they only disagree on 16 v. 9: Smith says to surrender, Shackelford says to hit. I haven't compared their H17 charts yet.

They also disagree on H17 games. Smith says to surrender the following hands in SD games while Shackelford says not to surrender: 16 v. 9, 15 v. 10, (8,8) v. Ace. Shackelford says (7,7) vs. 10 should be surrendered, whereas Smith says it should not be. There are 2 DD differences: Smith says (8,8) v. Ace and 16 vs. 9 should be surrendered, whereas Shackelford says they should not be.

My guess is that Shackelford is correct because Smith's BS charts give the same surrender strategies regardless of the number of decks, which doesn't make much sense. According to Smith, the same hands that should be surrendered in an 8D game should also be surrendered in a SD game; the only differences in his surrender strategies are between S17 and H17.

With whom do the pros out there agree?

For SD, s17: 7,7 v. 10; 9,6 and 10,5 v. 10; 9,7 and 10,6 v. 10; and 10,6 v. A.

For SD, h17: 7,7 v. 10; 9,6 and 10,5 v. A; 9,7 and 10,6 v. 10; 7,7 v. A; 9,6 and 10,5 v. A; 9,7 and 10,6 v. A; and 10,7 v. A.

For DD, s17: 9,6 and 10,5 v. 10; 9,7 and 10,6 v. 10; 9,7 v. A; and 10,6 v. A.

For DD, h17: 9,6 and 10,5 v. 10; 9,7 and 10,6 v. 10; 9,6 and 10,5 v. A; 8,8 v. A, if no das; 9,7 and 10,6 v. A; and 9,8 and 10,7 v. A.

Don

For SD-H17, you say that (7,7) v. Ace and (9,7) v. Ace should be surrendered, whereas Shackelford does not. For DD-H17, you say that (8,8) v. Ace should be surrendered if DAS is not allowed, whereas Shackelford does not. I believe you have said that Shackelford is always correct, and everybody knows how precise you are, so who's correct here?

"For SD-H17, you say that (7,7) v. Ace and (9,7) v. Ace should be surrendered, whereas Shackelford does not. For DD-H17, you say that (8,8) v. Ace should be surrendered if DAS is not allowed, whereas Shackelford does not."

I haven't checked Mike's site, but I'll take your word for it.

"I believe you have said that Shackelford is always correct,"

He tries very hard, but, in the past, I have pointed out to him several typos and/or errors on his site.

"and everybody knows how precise you are, so who's correct here?"

Blush, blush -- what can I say? :-)

Don

But how do you account for the differences?

I neglected to add 7+7 and 9+7 Vs. A under single deck, H17. No excuses, I blew it.

For 8+8 Vs. A, DD, H17, I show the player should surrender if DAS is not allowed and should split if it is allowed. My program uses some shortcuts on splits, and this play is possibly within the small margin of error. Cacarulo's table (see link) agrees if DAS is allowed but he doesn't have a table for DD, H17, no DAS. I would be interested in his or Don's confirmation on this play.

2D,H17,DOA,SPL3

1) 8,8 vs A (DAS)

Standing  =  -58.69033300135978%

Hitting   =  -53.13212295637489%

Doubling  = -106.26424591274977%

Splitting =  -49.38608821929895%

Surrender =  -50.00000000000000%

2) 8,8 vs A (NDAS)

Standing  =  -58.69033300135978%

Hitting   =  -53.13212295637489%

Doubling  = -106.26424591274977%

Splitting =  -50.04672401199956%

Surrender =  -50.00000000000000%

"But how do you account for the differences?"

Simple. No one was 100% accurate in this case. Read 10 books that purport to offer "perfect" basic startegy, and eight will disagree!

Don

The majority of books are flat-out incorrect about Basic Strategy.

that offers precise, detailed information for complex situations such as those discussed in this thread, which one would it be? "Theory of Blackjack" maybe?

I've admired your work for a long time but can't recall ever seeing you post on the BJ boards. Thanks for all the accurate info on your site.

Since surrender is the correct play for both 9,6 and 10,5 vs. 10 (as your appendix shows), shouldn't your SD basic strategy charts have the designation of H/R instead of H for 15 vs. 10? I figured that would be more logical since there is only one type of hard 15 (8,7) that should not be surrendered. Also, there is no designation on your DD-H17 BS chart for surrendering on 8,8 vs. Ace with no DAS.

Thanks a lot for all of the fantastic info. you provide on your site.