Talk:Karnaugh map

Contents

1 Veitch Diagram 2 Grey code 3 wrap around 4 rectangular circling 5 Pronunciation 6 Second diagram

Veitch Diagram

Although there is now a referance to the Veitch diagram, this is a little misleading. The Karnaugh Map is a special case of a Veitch Diagram. Although the original form of the Veitch diagram doesn't enjoy any sort of use now.

This also conflicts with the idea that the Karnaugh map was 'invented' in 1950 - it is more properly an extension of existing work. Anyone have any thoughts on how to resolve this? NVeitch

Hm the C,D-row is upside-down. It should go as (0,0)-(0,1)-(1,1)-(1,0). --BL

Grey code

Perhaps we should mention that the rows and columns are ordered according to a grey code, or otherwise explain the importance of having precisely one input value flip between adjacent boxes. Bovlb 00:37, 2004 Mar 11 (UTC)

wrap around

Should there be mentionted that a K-diagram is wrapped around?

So the top left and top right connect and the same goes for bottom left and bottom right.

Kind regards

rectangular circling

Should there be a mention that the cells need to be cirlced in a rectangular shape?

Pronunciation

What is the correct pronunciation of Karnaugh's name? Stern 00:00, 1 Dec 2004 (UTC)

Same as Carnot, or CAR-NO. Graham 00:08, 1 Dec 2004 (UTC)

Second diagram

What's the purpose of the second diagram? I don't understand it, it appears to duplicate the first with a less clear labelling, and the text doesn't refer to it. I think it should go. Graham 00:29, 21 Dec 2004 (UTC)

It is an alternative syntax, the one we were taught at the university. I actually find it much more clear than the first one: in this one you can see directly where A, B, C and D are ON and where they are OFF just by looking at the line/row. It should actually be rotated 90 degrees so that it could be drawn more directly from the truth table of the function (and so should the already existing map). I'll create an improved version and add a description of it to the article soon. --ZeroOne 17:57, 21 Dec 2004 (UTC)

OK, you can see the improved version here. Refresh the image if it doesn't differ from the one you saw - it is updated:

Missing image
Karnaugh_map2.png
Image:Karnaugh_map2.png

The little numbers at the corner of each square are the row numbers of the truth table of the function. It is otherwise from 0 to 15, left to right, up to down but the two last columns and two last rows are flipped. There's nothing strange in that, the existing map has the same feature, too. The area "A{", two last rows, is where A is 1. The area "}B", two middle rows, is where B is 1. The area "C{", two last columns, is where C is 1 and the area "D{", two middle columns, is where D is 1. What do you think now? --ZeroOne 18:41, 21 Dec 2004 (UTC)

Weeellll.... to be honest I've been using Karnaugh maps for years and have never seen this form. I'm trying to figure out exactly what it is portraying just by looking at it, and I'm afraid I still don't get it. Maybe I'm just too used to the "old" form. Seems to me the need for the row numbers to be put in each square to help make sense of it mean it might not be as effective as the "old" type - with that one, I can see at a glance what the terms need to be and can simply write them down without any interpretation - but again I'm willing to put that down to familiarity. The flipping of the columns you mention is indeed a feature of the normal map - that's because the bit ordering needs to follow a gray code - something that the article fails to mention, but probably should. Maybe the explanatory text you plan to write will help the lightbulb go on, but the diagram on its own doesn't work for me - but maybe others here will have more to say about it? Graham 22:39, 21 Dec 2004 (UTC)

You don't need those row numbers, you learn them quickly and can always deduce them again should you forget them. Actually the map I'm showing is no different from your map: it just emphasizes the ones better. That is, the rows and columns where a certain variable is 1 are "grouped" with the {'s. The squares which do not belong to a given group belong to the negation (where the variable is 0) of that group. I found a nice picture from the teaching material of my university: [1] (http://wooster.hut.fi/digis/luento4/4kartta.gif). It combines both of the maps in the same picture (because they actually are the same map). Maybe *that* will explain it to you too? :) To add, to me the current map looks almost like if it had 8 rows and 8 columns. The amount of variables shown is too big to handle effectively. --ZeroOne 23:22, 21 Dec 2004 (UTC)

Ah, OK, I get it now. The image on your uni site adds the crucial "lightbulb" detail for me - the AB/CD labelling in the top corner. That said I'm not really convinced that this method is really any better than the normal one - perhaps I was expecting the advantage to be much greater than what is really just a small change to the way the columns and rows are labelled. I'd like to hear some other opinions on this though. By the way, the appearance of 8 columns rather than 4 is not something I'd really found before, since it's clear to me that it is PAIRS of variables that are being considered by each column. Graham 23:47, 21 Dec 2004 (UTC)