Manaweaving and sufficient randomization

[diskord]

Interested in thoughts on a topic that came up in a recent tournament. It involves a player whose attitude to the game I respect greatly, and I wondered on an experienced judges attitude.

Essentially, before our game he separated his deck into land and spell, and proceeded to face-down manaweave, LSSLSLSSLS etc.... I asked him why he was doing it and he said, and I paraphrase 'If you start with land together, you end up with land together'. I commented that the same holds for weaving, and he was dismissive. He followed up the weave with a pile shuffle and several riffles and overhand shuffles.

Is this illegal? My standpoint is that the player, by actively un-randomizing his deck prior to shuffling, is essentially stating that he will not sufficiently randomize the deck during the shuffle process. It takes energy to manaweave - if it made no difference to the final deck order, you wouldn't do it. And if it makes a difference to the actual deck order, you're not allowed to do it. Am I missing something really obvious? Is manaweaving illegal even if you randomize afterward, and how do you check?

Thanks for any insight.

[Drakonis Mage]

Technically it's illegal. That quote would make me suspicious as to how well he's randomizing his deck as well.

In fact, from his approach, I'd call it stacking his deck personally.

If so, then it's definitely a procedural error-major. (not sufficiently randomizing deck before handing it over to opponent).

20. TOURNAMENT MECHANICS

21. Shuffling
Shuffling must be done so that the faces of the cards cannot be seen. Regardless of the method used to shuffle, players' decks must be sufficiently randomized. Each time players shuffle their deck, they must present their deck to their opponent for additional shuffling and/or cutting. Players may request to have a judge shuffle their cards rather than pass that duty to their opponent, this request will be honored at a judge's discretion. By presenting their decks to their opponents, players are stating that their decks are correct, legal, and sufficiently randomized.

[epeeguy]

To add another perspective (Drakonis is spot on), the only reason to mana weave is in order to affect the distribution of cards in the deck; which, by nature, means that the deck is not going to be sufficiently randomized when it is shuffled. This can be seen by taking any deck of cards, ordering the contents, and then riffle shuffling. When viewed, the contents of the deck will still have a somewhat recognizable pattern to them, based on how they were ordered.

This is especially true with manual shuffling, which is not "true randomization". In a system that used "true randomization", the contents of the deck could be conceivably put in any order possible. That's not entirely true with manual shuffling. With manual shuffling, due to its very nature, certain cards are going to remain in certain spots in the deck. Cards that are near the top third of the deck will usually remain there while being riffle shuffled, while cards near the bottom third will remain near the bottom. Cards in the middle can be distributed towards the bottom or top, depending on how the deck is cut.

Magician/Sleight-of-hand tricks generally use these kinds of processes in order to "fix" the results; which is no different than mana weaving. You basically order the deck, and the shuffle will not distribute the cards evenly enough to ensure the "sufficient randomization" standard is met. While it may be that land (or any other card really) seems to clump together, this is not a reason to order the cards in the library. All I can recommend is that a player use a combination of pile shuffling (itself a form of ordering) and riffle shuffling in order to break up clumps like this.

One pile shuffle followed by several (more than 5) riffle shuffles is usually sufficient to ensure the deck is "sufficiently randomized"; and even then, sometimes the distribution of land in the deck is "bad" (but, that's the nature of this, and is actually a reasonable and acceptable result, even if it sucks).

Note: if the player knew what he was doing, and was doing this intentionally, then it can be considered Cheating - Other. This is an offense against the rules which warrants a DQ.

[diskord]

Thanks guys.

I have no reason to believe he was actually cheating, rather I would suspect that it's the common problem of not understanding the meaning of 'sufficient' or 'random'.

Knowing that it comes in under Proc. Error - Major is useful, though. And the '1 pile + 5 riffle' rule is handy to keep in mind.

I may have to do the little randomness talk with everyone in my local group.

[epeeguy]

Knowing that it comes in under Proc. Error - Major is useful, though. And the '1 pile + 5 riffle' rule is handy to keep in mind.

And just to be aware of this; the "5+ riffle shuffles" actually comes from studies that have been done with cards and shuffling to achieve a certain level of randomization. This is not something that was just "made up" for someone's standard, it's an actual statistical study that has been performed by mathematicians.

If I can dig up the link, I will, but the general theory is that with a deck of 52 cards, you can conceivably achieve randomization with between 5 and 7 shuffles. The more cards, the more shuffles needed. So, with 60 cards, about 6 riffle shuffles are plenty to achieve some sufficiency here.

[diskord]

Would definitely be interested in the link, thanks.

Is there any issue with 'perfect' riffling? I.e. 1-1-1-1- from each section. Can that maintain card distribution?

Sorry for the repeated q's, but you guys seem to know what you're on about...

[Zim Zam McGoo]

Eight perfect riffles leads to the deck being exactly as it was before, if you lead with the bottom half I think, or maybe the top (don't remember that part). It's virtually impossible to accidently do a perfect riffle though, magicians spend years practising it. It's just something I read on a web site once, and tried it out by putting the cards together one at a time - it actually does come back to the same.

[epeeguy]

I've heard of being able to return your deck to its original configuration with 8 perfect shuffles as well. I've never been able to find where that comes from though. Regardless, here's a few links to process:

http://en.wikipedia.org/wiki/Shuffling_playing_cards

http://www.kibble.net/magic/magic09.php

http://www.sciencenews.org/articles/...4/mathtrek.asp

Those are just a few of the links I could find on the subject.

[diskord]

Thanks for the information.

Re: the difficulty of perfect riffling - it's very difficult with playing cards, because they're quite stiff and, crucially, the same thickness all the way to the edge. Magic cards in sleeves have a slightly flexible, slightly thinner edge where the card isn't, which makes it an awful lot easier to perform very accurate riffles.

I've put some practice in, and it's still hard, but easier.

[PhyrexianSurvivor]

Before someone suggests this, I'm going to go ahead and say it. If you know your opponent is doing something like this, call a judge. Do NOT:

Shuffle pile your opponents deck into three piles, then put them together without shuffling them. If you know you can change your opponents deck to have all spells or lands on top, and you rearrange his deck to do so, you're cheating just as badly as he is, and he could call a judge on you.