Leads and signals

Wbridge5 defends by count. Its help file says so for the first seven tricks, and the probes below confirm it for the opening lead and for the first card it plays from each suit, whether it follows, discards or ruffs. A high card followed by a lower one (high-low) shows an even number of cards. The lowest card shows an odd number.

The probes played each deal over the Table Manager protocol, to trick 1 unless a section says otherwise, with nobody vulnerable and the program’s default card play options: signals on for the defense, 4th-best leads against notrump on, and Vinje off. The options are in the [WBR5] section of WBRIDGE5.INI, not with the bidding conventions in [Ench]. Hands below show the led or followed suit; x is any spot below the 8.

Count signals

These probes gave North the ace and king of a suit and had North lead the ace, with dummy playing low. Wbridge5 followed with:

• Odd number of cards: the lowest card, 261 of 270 times outside the trump suit and 156 of 157 in it.
• Even number: a high card, chosen so it cannot be mistaken for the lowest:
  • the highest spot below the 8 that is not the lowest card, e.g. 7 from J874 or 6 from 8654 (215 times);
  • with no such spot, the 8, e.g. from J1085 or 10987 (59 times);
  • with only an honor or the 9 above the lowest card, usually the 9 or 10 (50 of 68), with the jack about half the time (20 of 32), but almost never the queen. From Qx or QJ9x it plays low (25 of 27).

The rule is the same against notrump (385 deals) and in a side suit against 4♠ (365 deals). Under partner’s ace, it sometimes plays an honor from a sequence instead, such as the queen from QJ109xx.

Following in the trump suit is also count, not Vinje: the shape of the rest of the hand does not matter. Wbridge5 is stingier with high trumps, though. With only the 10, jack, or queen above its lowest trump, it played low 48 of 49 times. The 9 still signals (13 of 19), the 8 usually (13 of 17), and a spot below the 8 always (89 times).

Vinje, which shows the hand’s pattern with the trump card, is an option in the Options menu. It has no WBRIDGE5.INI key, so its effect was not probed.

Later tricks

These probes played on to trick 8 or 12. The probe script played declarer, dummy and partner by a fixed rule: lead a suit Wbridge5 was void in, else the top of the longest suit, and win as cheaply as possible. South held 0–9 HCP and defended 3NT or 4♠, often void in a suit to force discards and ruffs.

The first card Wbridge5 plays from a suit is a count signal, by the same rule as under partner’s ace. In tricks 2–7:

The even column leaves out holdings with only an honor or the 9 above the lowest card.

• Discards are count, not always the smallest card as the help file says: the 7 from J743, the 6 from 8642, but the 2 from A9532. Which suit it discards from follows no simple rule of length or strength.
• Ruffs show trump count: the 8 from Q1086 or the 6 from J652, but the 2 from J9732.
• Later cards in the suit are usually the lowest, completing a high-low after a high spot 173 of 181 times, and 263 of 333 times after a low one.
• After trick 7, the help file’s limit, few first cards are left. They still looked like count: the lowest from odd 25 of 28 times, a high spot from even 11 of 19.
• Winning a trick, it plays the lowest of touching cards (44 of 45).

Suit preference

Wbridge5 gives count where many players signal suit preference.

• Under partner’s ace with dummy void in the suit against 4♠, it still gave count on 10 of 10 boards, and on 41 of 43 with a singleton in dummy.
• Partner leads for a ruff: partner led the top of a suit Wbridge5 was void in against 4♠. It ruffed dummy’s winner every time (63 boards), with the count card above, and returned clubs or diamonds about evenly after a high or a low trump. It discarded under partner’s winner 41 of 51 times, also a count card.

Opening lead against notrump

Wbridge5 leads a suit of 4 or more cards, unless partner bid a suit. Over 1NT - 3NT it led its longest suit 237 times and a shorter 4-card suit 29 times out of 266; it never led a suit shorter than 4. Over a passed 1NT, the same hands led the same card 228 times.

A 7-card KQ10 suit led the queen (KQ109873, KQ108632, 2 hands). A 4-card suit headed by the ace was led from the bottom, 4th best, like any other.

With the 4th-best option off (4_longueNS=0), 153 of 172 leads changed. The card follows the method against suit contracts below, and the suit changed too, on 103 boards.

Opening lead against suits

Wbridge5 likes short suits against suit contracts. Over 1♠ - 4♠ it led a singleton 27 times, a doubleton 75 times, and trumps 26 times out of 229.

The card is the count signal again:

• Doubleton: top (107 of 108 small doubletons), including Jx
• 3 cards: lowest, from xxx, Jxx, Qxx, Kxx, Q10x (43 of 48 small tripletons)
• 4 cards: the same high spot as when following: 6 from 8654 or Q654, 7 from J875, 8 from J983, but the 10 from 109xx
• 5 cards: lowest
• Touching honors: the top one: KQx, KQxxx, QJxx, J10x, AKx, AKxx, and the king from AK doubleton
• Interior sequence: the 10 from K109xx and Q109x
• An ace: led, not underled: Ax, Axx, Axxx, AQxx, AKJxx, AKQxxx

The help file adds that a king lead promises the queen and a queen lead the jack, except in partner’s suit.

Opening lead against slams

These probes dealt Wbridge5 0–9 HCP and compared the same hands against game and slam. Its leads are deterministic: rerunning 103 hands against 3NT and 4♠ repeated every lead. It changed the lead on 250 of 275 hands from 3NT to 6NT, and on 156 of 246 from 4♠ to 6♠.

Against 1NT - 6NT, the lead is passive. It led from a suit without an honor above the 10 on 180 of 275 hands, never a 4th best, and a suit of 4 or more only 96 times (always against 3NT). The card is the count lead against suits: top of a doubleton (xx 47, 10x 13, Jx 10), lowest from 3 (xxx 33), a high spot from 4 (xxxx 11), and the top of touching honors (J10xx, KQxxx, AKxx).

Against 1♠ - 6♠, it cashes an ace: 79 of the 121 hands with an ace led one, against 15 of 117 against 4♠, e.g. Axx, Axxx, A10xxx. It led fewer short suits than against 4♠ (singletons 20 and doubletons 38 of 253, against 35 and 87 of 248) and about as many trumps (19 against 24).

Doubled contracts

Partner doubled the final contract after the same auctions, with the same hands:

Partner’s suit

When North overcalled 2♥ and East-West reached 3NT or 4♠, Wbridge5 led a heart 72 of 74 times against 3NT and 137 of 167 times against 4♠. The card is the count lead: top of a doubleton, lowest from 3 (64 of 84), and a high spot from 4. It is readier to lead an honor than in its own suit: the king from Kxx or K10xx, and the queen from Q10xx or Qxxxx, now and then.

Not probed

• The help file’s limit of seven tricks: few first cards from a suit come later
• Attitude signals, and Wbridge5’s own suit-preference card when it gives partner a ruff: it picks its own leads, so the spot cannot be forced
• How Wbridge5 reads partner’s signals: the probe script’s partner signals nothing
• Defense against a sensible declarer: the scripted declarer cashes its long suits and leads Wbridge5’s void. Against 4♠, Wbridge5 sometimes hung computing its play after such a line.
• Leads by a passed hand
• Leads from AKQ against notrump, and from AK doubleton against notrump
• Vinje, and how Wbridge5 reads a human partner’s cards with the Signals option on