Sysudoku Speak

This is a glossary of terms used in Sysudoku posts and pages.

1-way – an alternating inference chain (AIC) starting on a weak link and ending in a weak link into a victim candidate seen by starting candidate. If the starting value is true, the victim is false by “seeing”.  If the starting candidate is false, the AIC carries  the false inference “one way” to the victim.

3-fill – a line with three cells not assigned a value. Also the method of assigning a value to a 3-fill cell because the cell is seen by outside candidates of the two other missing values, or because two other cells of the 3-fill are seen by outside candidates of a missing value.

4-fill – a unit with four cells not assigned a value, that resolves to a 3-fill because an outside candidates of a missing value sees three of the unassigned cells. 4-fills are marked only when effective.

AIC or Alternating Inference Chain – a chain of alternating strong and weak links.

AIC building – a late stage of Sysudoku Advanced, when X and XY AIC are exhausted, and AIC of mixed types are explored. At this stage, AIC are started with multiple ending possibilities in mind. Explored AIC may be is kept on a separate grid for possible extension in new AIC.

almost nice loop (ANL) – an alternative inference chain closed by one extra wink or slink. If the extra link is a wink, the candidate between winks is removed. In Sysudoku posts, enclosing winks of an ANL removal are omitted. If the extra link is a slink, the candidate between slinks is confirmed.

ALS – an almost locked set,  a set of n cells in the same unit containing n+1 values.

ALS AIC – an AIC including one or more ALS nodes.

ALS node – An ALS functioning as an AIC node.  Two outside candidates, each seeing an ALS value-set, are weakly linked by the ALS node, because if either outside candidate is true, its value-set partner is erased, and the other outside candidate seeing another value-set is false.

ALS value set – a set of candidates of a value in an ALS. The value sets are strongly group linked, because, if one value-set is deleted, all remaining sets are locked.

ALS-wing – an AIC of three ALS nodes. A search option of the Philsfolly solver. This includes cases in which ALS are bi-value cells.  In this example, the strong link between 5 and 6 value sets in the red ALS node carries the ANL inference, and value set 7 is a terminal group.

ALS_XZ –  A candidate removal in which X value sets of two ALS are weakly linked. One must be ultimately lost, locking its other sets. An outside candidate sees both sets of another value Z.

ANL, almost nice loop– an alternative inference chain closed by one extra wink or slink. If the extra link is a wink, the candidate between winks is removed. In Sysudoku posts, enclosing winks of an ANL removal are omitted.  If the extra link is a slink, the candidate between slinks is confirmed.

Avoidable rectangle – a basic removal to avoid a possible reversable unique rectangle.

Such as NE8 => N9 at r2c4.

BARN or Bent Almost Restricted n-set – A set of n cells containing n values in a bent region, with candidates of all but one of the values seeing each other. An outside candidate seeing all values of this group must be removed.

An n-BARN contains n values. If it is confirmed, there will not be enough values for the cells.

Basic, Sysudoku Basic – The identification of candidates, placements and links determined by the givens, in progress.

Beeby – A public solver provided by Phillip Beeby at

bent region – the union of cells in a box and a crossing line. In Sysudoku posts, the bent region of the box/line is identified by the box name and line name.

Blank Line Tally – a technique of marking regular fish on an X-panel. At least one blank row and blank column are required. Fish lines are marked with dashes, crossing lines, by plus signs.  Candidates in crossing lines, and not in fish lines, are removed.

BNS-0 – bent naked n-set zero, n cells containing n values in a bent region, with no  values in both remainders.  Each value set has a true candidate, and is therefore locked. Candidates outside of the intersection that see an entire value set must be removed.

BNS-1 – bent naked n-set one,  n cells containing n numbers in a bent region, with one value in both remainders outside of the intersection. The remainder candidates of this value  include a true candidate .  A BNS-1 is a BARN.

boomerang, boomer – an AIC loop starting with a slink and closing with a wink into a second candidate of the starting cell. If the cell has 3 or more candidates, an internal wink closes the loop and the re-entry candidate is removed. Boomers are normally spotted in the AIC building stage of Sysudoku Advanced.

box – A block of 3 x 3 cells to contain 9 values in the solution.   Boxes are designated by compass points in Sysudoku, lines by row or column number, and cells by row and column.

box marking – first stage of candidate finding based on outside clues excluding value from boxes.

box/line – removal 0f a  candidate in a box(line) because its value in another  intersecting line(b0x) is confined to the box (line), and cannot be  anywhere else in the box(line).

The 9 ANL removal confines r2 9’s to NW, removing 9r1c13. The 2 1-way and red extension confine N 2’s to r3, removing 2r3c2.

bv – a binary value cell of two candidates after line marking.

Bypass or slink marking bypass – the first stage of Sysudoku Basic, in which slink marking is left implicit while clues and subsets are marked.

chute – The intersection of a line and a box, a bent region.

cluster – a coloring link network marked by two opposing colors. Candidates of one color are true, and those of the opposing color are false.

coloring – the marking of coloring link networks (clusters) by two opposing colors. Most frequently used colors for Sysudoku colors are blue/green, then red/orange.

coloring link – a strong link (slink) based on exactly two candidates of a value in a box or line.

complex 1-way – a 1-way AIC with branching winks (dotted curve) making removals to activate slinks traversed later by the chain.

dublex or double line exclusion – using clues in two lines crossing a box to confirm a clue in the third line of the box.

enumerating – “displaying every instance of”, as in enumerating the ALS

finned fish – a regular fish spoiled by an extra candidate(s) (the fin) in the fish lines, but still effective on a victim candidate in the same box as the fin.

forcing chain – an alternating inference chain starting with a weak link, it extends “seeing” across the grid in many methods.

freeform – a representation of a pattern as a graphics freeform (of connected line segments) reaching across the an X-panel.

freeform analysis – determination of possible patterns (and pattern properties) of a value based on freeforms.

group – a set of candidates of the same value in a unit. Not necessarily containing all candidates in the unit of that value. A group is false if it contains no solution candidate of its value. A group is true if it contains a solution candidate. A candidate sees a group if it sees every candidate of the group. Groups are represented by thick solid curves or enclosing curves.

hidden dublex – a dublex or double line exclusion in which a clue in the third line of the box is forced by pencil marks in two lines.

kraken fish – a finned fish with a victim candidate outside the fin box seeing the fin by by means of an AIC.

line – a row or a column.

lite color or coloring – identifying candidates which are true when a cluster color becomes known to be true.  Such candidates are said to be of the “lite”color.

In Sysudoku, lite candidates are marked by arrows, rather than opposing cluster colors.

73c8 and 3 r3c1 are lite boyfriend traps. 3r4c8 is green lite and orange lite.

locked set – a set of candidates of a value in a box, line or ALS, which include the true candidate, and therefore cannot be removed.

LPO – Limited Pattern Overlay: Pattern overlay methods involving a small number of values, such as TVO.

Medusa Coloring – coloring that includes two candidates in a cell as a color link. Coloring based only on two candidates in a line or box is simple coloring.

nice loop – a closed alternating inference chain.  End candidates of every link are toxic sets.

nice loop – a closed, entirely alternating AIC, as r24c48 here.  Every link includes a true candidate.

nice loop coloring – Alternate node coloring in nice loop creates a cluster. A nice loop cluster is valid in multi-cluster methods, and can be extended along coloring links.

orphan – a candidate included in no pattern of its value.

The provable orphan is 1r1c5.

pattern – a distribution of candidates of a value that places one candidate in each unit. One pattern contains only true candidates.

pattern coloring – analysis of patterns by building coloring clusters of a value across lines and boxes.

pattern slicing – The division of patterns into disjoint sets by pattern coloring, usually for trials.

pencil mark –a small font digit representing the presence of a candidate in a cell.

pink/olive analysis – Pattern coloring analysis. Pink and olive are used to clearly indicate coloring by patterns.

placement – an assignment of a solution value to a cell.

Sashimi fish – a regular fish with a fin group in place of a missing candidates in one line.

sees – is a weak link with

slink – strong link: a link between candidates in which at least one partner is true.  If one slink partner is false, the other partner is true. A slink is represented by a solid curve.

slink marking – the Sysudoku pencil marking that uses candidate position within the cell to mark slinks and aligned triples.

slink marking bypass – the first stage of Sysudoku Basic, in which slinks are not pencil marked.

slink marking – the Sysudoku pencil marking that uses candidate position within the cell to mark slinks and aligned triples.

subset –a subset of n cells in a uit containing n values.

suset – a pair of digit strings identifying cells and the values these cells contain. Susets define ALS, subsets and fish.

suset enumeration scratchpad – a hand calculation algorithm for enumerating almost locked sets in Sudoku. Developed in Sysudoku and applied to finned and regular fish, ALS and locked sets. Detailed in The Guide/Sysudoku Basic.

Sysudoku Advanced – solving methods based on relations among completely identified candidates.

Sysudoku Basic – starting procedures in Sysudoku to find subsets and clues and slink markings, along with all candidates.

toxic set – a set of candidates determined by a pattern to have at least one true candidate. A candidate seeing the whole set is removed.

trace – A recording of basic solving events. New clues and subsets are displayed in solving order, without explanation. Traces are read by adding clues and subsets in the trace order to the reader’s grid. Traces are explained on the Sysudoku Traces page, but are best understood as a written confirmation of the reader’s next move.

Above is World’s Hardest 103 basic trace, recorded during Sysudoku Base. The trace here records the basic moves of the wrap of green in the solution of World’s 103.

trap – a coloring or lite coloring candidate removal based on its seeing like value candidates of opposing colors. One opposing color of a cluster is true.

This is three World’s 103 traps.

trial – In Sysudoku, a true or false test of a set of logically connected candidates,

trial-and-error – a sudoku term generally applied to trying out guesses, i.e. assertions not derived logically from existing candidates.

trial trace – A trace for identifying a contradiction in the shortest chains of inferences(see Sysdsoku Traces).

true candidate – A candidate that is in the solution.

Two Value Overlay (TVO – A pattern overlay of two values. Between them, two cells are included in every pattern on one value, but these two cells are required in the true pattern of another value. All patterns of the other value including these two cells are eliminated, possibly revealing orphans of the other value.  

In a Beeby TVO example, a W>E 5-freeform not starting in r5c3 lands in r9c7. 7r5c3 is removed, because any 7-freeform including r5c3 starts in 7r3c1 and both of them fail. The true 7-pattern does not include 75c3.

unit (aka house) – a box, row or column.

UR, unique rectangle –removal methods based on a candidate being true will bringing a rectangle of solutions of two values that can be interchanged to form a second solution.

In this DIY UR, 5r3c3 would erase 3 extra candidates, leaving a reversable rectangle.

A Sysudoku Advanced page, The Unique Rectangle explains types of UR, and the Solving Tools page begins with a corresponding table

value – a term used for one of the digits 1 – 9, in place of the term “number”.

value set –  candidates of the same value in an ALS.

wink, weak link – a link between candidates in which both partners cannot be true. When one is proved true, the other is false. On Sysudoku grids, winks are dashed curves.

wrap – the determination that a cluster color is false. The opposing color is confirmed.

X-chain – an AIC of candidates of a single value (X).

X-panel – a set of tables showing the remaining candidates of each value, without clues.

XY-chain – an alternating inference chain linking bv cells with winks, alternating with internal slinks of bv.

XY railway – a set of curves on the bv map showing possible paths of XY-chains. A tool for spotting XY chains.

8 Responses to Sysudoku Speak

  1. Andi says:

    … So my question is, what are some logic rules to get going? With the other ones the strategy is to start from the corners and sides and work inwards. So without the walls, where is the logic to start (the 4s or 2s)?

    • Sudent says:

      Andi, you’re at one of the few places to explain how to start. It’s in the earliest posts of September/October 2011. The beginner’s page is a prep to these posts. You start by finding some candidates which work to help you find all of them. That is basic solving, in two stages. Then with all the candidates you can do advanced strategies. In fact that is the definition of advanced strategies, the ones requiring all candidates.

  2. Alexandra says:

    thank you for sharing all this great information.

  3. Betina says:

    your website is so organized, and your posts are always common sense, congratulations for making the difference.

  4. Hey, you used to write magnificent, but the last several posts have been kinda boring… I miss your super writings. Past several posts are just a little out of track! come on!

    • Sudent says:

      Hey, Cris, you’re right on! As the messages got as complex, I got stodgy. Thanks for the nerd alert! I’m gonna lighten up.

      A note to everybody: Please comment on the relevant post. Cris could have made plain for future generations exactly where he detected uncharacteristic stoginess.

  5. Stranford says:

    I think other web-site proprietors should take this web site as an model, very clean and excellent user friendly style and design, let alone the content. You are an expert in this topic!

  6. Rudolph Heglund says:

    9/5/2016 Like the website– extremely easy to navigate and lots to consider!

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