## Forcing Chain / Nice Loop / Bivalue Plot question

Advanced methods and approaches for solving Sudoku puzzles

### Forcing Chain / Nice Loop / Bivalue Plot question

So, I've been reading up on forcing chains & bivalue plots as these seem to be the next level of technique I need to acquire to solve the really tough problems, and the following question has come to mind.

For those of you out there that are working on these tough problems using these techniques, are you doing this work by hand on paper, or are you using some type of computer software?

I tend to enjoy solving puzzles using software because I can avoid the tedium of having to write in all the pencilmarks and erase them as eliminations are made. I also really like Simple Sudoku's filtering and coloring features (although sometimes I wish there were 6 colors instead of 4).

Anyway, I have not really gotten to the point where I can identify these chains, nice loops, etc. in my head, so I'm wondering if everyone else out there is doing this stuff with pencil and paper.

Thanks,

Jeff
JeffInCA

Posts: 33
Joined: 02 January 2006

Hi JeffInCA.

As far as I am concern, I solve most puzzles just by hand and paper. Although writing all the pencilmarks by hand can be tedious, in my opinion it can be quite useful for identifying nice loops. Indeed, I think that nice loops (and other techniques) can be more easily applied using paper (if a correct pencilmark writing approach is used). But, of course, this is just a personal opinion.

Regards, Carcul
Carcul

Posts: 724
Joined: 04 November 2005

I usually use Simple Sudoku to fill in the pencil marks, then either print it out or do a screen capture (SS has a "capture as image" feature.) and paste it into Paint Shop. If find it faster and easier on paper but more convenient in Paint Shop.
tso

Posts: 798
Joined: 22 June 2005

Jeff (not InCA) has just started an Identification of forcing chains thread. I'm sure he would love to hear from all of you over there.

Ron
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

I will actually fail to spot them in 9 out of 10 times, unless I am near the endgame where the unsolved cells have bivalued candidates.

Forcing chains can be very complex (leading to sequential advanced subset implications), I think that is difficult to spot by the human eye looking at the raw pencilmarked grid.

tarek

Posts: 2909
Joined: 05 January 2006

ronk wrote:Jeff (not InCA) has just started an Identification of forcing chains thread. I'm sure he would love to hear from all of you over there.

I, and other readers would love to hear from you too, Ronk.
Jeff

Posts: 708
Joined: 01 August 2005