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## Re: [Bug-gnubg] Small oddity in CalculateHalfInputs()

 From: Joseph Heled Subject: Re: [Bug-gnubg] Small oddity in CalculateHalfInputs() Date: Thu, 19 May 2005 07:35:43 +1200 User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050509 Debian/1.7.6-1ubuntu2.1

```Jon Kinsey wrote:

```
```Jim Segrave wrote:

```
```On Wed 18 May 2005 (08:06 +0100), Jon Kinsey wrote:

```
```Jim Segrave wrote:

```
```I've been looking at this function as I belive it can be recoded to
provide more efficient setup of the NN inputs. As a first step, I've
been going through the code looking at the sections that produce
various inputs. One of the very first ones is the routine to calculate
the number of pips needed to break contact:
```
```
```
```[snip]

```
```No, 6 points breaks contact - you don't have to go any further than
off.
```
```

I was confused - and thought it was the piece on the bar that was being
counted not the other way around.

```
```
```
```now if instead nOppBack = 0 (1 pt) gives:
nOppBack = 0 (1 pt), i = 5 (6 pt) gives:
i + 1 - nOppBack = 6
```
```

Breaking contact with a man on the 1 is no different than with the man
on the bar, you only break contact by bearing off
```
```

You're right, but is that all the code is doing?  Or more specifically
there is a difference (in the position) so perhaps the different values
help distinguish these positions in some way?

I really don't know much about the NN code, out of interest if this was
changed would it likely have any effect?  If so does that mean that
gnubg is slightly mis-trained for this specific circumstance?

```
Not necessarily. The net can compensate by combining the fact that there is a man on the bar (from the basic inputs). If you make such a change, you need to re-train all nets. From long and bitter experience, I suspect the improvement in such a case would be nil.
```
-Joseph

```
```Jon

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