Author Topic: Some questions about cross matching  (Read 8872 times)

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Some questions about cross matching
« on: 28 Jun 2013, 09:20 »
1. Are back_amount and lay_amount based purely on the actual amounts which are waiting to back or lay for the specific selection, or do they include the additional amounts betfair shows as available based on its cross-matching formulae?

2. Does enabling the option to "show prices exactly as they are on BF" make any difference to the answer to Q1?

3. Do actual bets on the selection get matched first?  E.g. BF is showing £100 available to back at 8, but that is all generated from cross-matching.  I lay at 8 for £100.  Is my lay bet front of the queue, or does the cross-matched amount get taken first?

All help gratefully received.
O

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Re: Some questions about cross matching
« Reply #1 on: 28 Jun 2013, 16:43 »
My understanding for what it's worth is:

1. Are back_amount and lay_amount based purely on the actual amounts which are waiting to back or lay for the specific selection, or do they include the additional amounts Betfair shows as available based on its cross-matching formulae?

The API according to Betfair cannot show virtual bets: see http://bdp.betfair.com/index.php?option=com_content&task=view&id=242&Itemid=68

2. Does enabling the option to "show prices exactly as they are on BF" make any difference to the answer to Q1?

It would appear to be a problem with the API so the answer is likely to be no. OXA would know better than me though.

3. Do actual bets on the selection get matched first? 

I don't know the full answer to this question. However, a virtual bet is always linked to real bet amounts and prices available on the other side. So, if the virtual bet is snapped up then the only way to balance the books is for the linked real prices/amounts being used to fund the virtual bet. In this situation your bet cannot have priority. Cross matching, after all, matches a virtual bet on one side with the real amounts/prices on the other side for all other selections in the market.

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Re: Some questions about cross matching
« Reply #2 on: 28 Jun 2013, 18:09 »
Hi
eeldergill is correct in pointing out the API does not show virtual bets.

There is an algorithm provided by Betfair Developers Program to allow API applications to display the virtual bets:
http://bdp.betfair.com/index.php?option=com_content&task=view&id=237&Itemid=62

however it occasionally displays a faulty price:
http://community.welldonesoft.com/troubleshooting-8/lay-price-equals-back-price/

In your example, yes your lay at 8 will join the queue. However, you are likely to reach the front of the queue quicker as the opposing real bets are matched on the other selections.   
Another example:
If there is a real bet on Over 2.5, Betfair will put up the opposing virtual bet on Under 2.5
It does not matter which is matched first, because effectively they are both matched at the same time.
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Re: Some questions about cross matching
« Reply #3 on: 30 Jun 2013, 17:35 »
What I can say for now since I'm new to this, is never to trust everything that you see in the API.
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Re: Some questions about cross matching
« Reply #4 on: 01 Jul 2013, 10:39 »
Hi Orzola,

I will try to answer to my best understanding.

1. Are back_amount and lay_amount based purely on the actual amounts which are waiting to back or lay for the specific selection, or do they include the additional amounts betfair shows as available based on its cross-matching formulae?

Both prices and amounts participate in cross-matching.

2. Does enabling the option to "show prices exactly as they are on BF" make any difference to the answer to Q1?

Yes, it does.

3. Do actual bets on the selection get matched first?  E.g. BF is showing £100 available to back at 8, but that is all generated from cross-matching.  I lay at 8 for £100.  Is my lay bet front of the queue, or does the cross-matched amount get taken first?

There is no direct explanation on this anywhere, but the way I see it your bet's position in the queue is defined by the time it was placed, regardless of the way the actual matching is performed.
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Re: Some questions about cross matching
« Reply #5 on: 20 Jul 2013, 11:05 »
Belated thanks to all for input on this.  Some of the answers were the exact opposite of what I was previously assuming, so were all the more valuable.   

O

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Re: Some questions about cross matching
« Reply #6 on: 21 Aug 2013, 21:34 »
I think there is a problem with the way the cross matching formula is working in certain circumstances.

I have noticed a problem in tennis matches when enabling the "show prices exactly as they appear on betfair" setting.

I have never had a problem on selection 1, but for selection 2 the amount showing as available to back has been showing on MF as roughly double the amount appearing on betfair.  I'm afraid I can't recall whether the amount available to lay was wrong as well.

Is this a known issue?
Thanks
O

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Re: Some questions about cross matching
« Reply #7 on: 24 Aug 2013, 08:14 »
Hi Orzola,

Yes, this is a known issue. BetFair does not provide an exact formula for calculating the prices and amounts in cross-matching which covers 100% cases. Therefore, sometimes those figures do not coincide with the ones on the web site.

They have announced that the new API will return correct figures for cross-matching, so this problem should be fixed once the program is converted to work with the new API.
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Re: Some questions about cross matching
« Reply #8 on: 24 Aug 2013, 16:13 »
Hi Oxa

Yes, I'd picked up that sometimes there would be slight (and I thought temporary) errors, but the ones I have been seeing are major permanent errors.

E.g. amount available according to MF £20,000 amount available according to betfair £10,000.  This has happened a few times, always on selection 2.

The amounts waiting to back on the other player were not nearly enough to account for the difference as a result of cross matching.  It seemed like a more fundamental problem to me.  I would try to find an example to illustrate, but I'm in Spain at the moment.

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Re: Some questions about cross matching
« Reply #9 on: 28 Aug 2013, 09:27 »
Oxa

Have a look at Dutra Silva v Nadal in the second round of the US open tennis:

On betfair

£129k / £82k  (1.01/1.02)

On MFPro

£259k / 162k

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Re: Some questions about cross matching
« Reply #10 on: 30 Aug 2013, 13:49 »
Hi Orzola,

Yes, I understand, yet I have no other explanation to that, as when I trace this problem to the piece of code responsible, I can see that it is due to the discrepancies in the theory of cross-matching and what they actually have on their web site.
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