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| | | Author: | Bobflip  | | Posted: | May 26, 2022 12:23 | | Subject: | Auto-select not prioritising cheaper item | | Viewed: | 72 times | | Topic: | Buying | |
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| There's a set of instructions on my wanted list, which is listed by three
sellers in the UK. They all show up in the filters, I have all the exclusions
unchecked and leave the minimum buy caveat enabled, but auto-select is selecting
the most expensive seller. The only difference I can tell is that the two cheaper
stores don't have a postage estimation, and the third store does. If I add
the most expensive one to the cart, auto-select now ignores it and it goes to
the cheapest one on the list.
So it seems the lack of a postage price is negatively affecting the results,
is there a way to disable it from being taken into account?
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| | | | | Author: | SylvainLS | | Posted: | May 26, 2022 12:47 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 29 times | | Topic: | Buying | |
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| In Buying, Bobflip writes:
| | There's a set of instructions on my wanted list, which is listed by three
sellers in the UK. They all show up in the filters, I have all the exclusions
unchecked and leave the minimum buy caveat enabled, but auto-select is selecting
the most expensive seller. The only difference I can tell is that the two cheaper
stores don't have a postage estimation, and the third store does. If I add
the most expensive one to the cart, auto-select now ignores it and it goes to
the cheapest one on the list.
So it seems the lack of a postage price is negatively affecting the results,
is there a way to disable it from being taken into account?
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Not that we (at least I) know of.
All we (users) know (or rather, could deduce from the tidbits we were given)
is that, in the choice of Auto-select, enter:
— an estimation of the postage (not the seller’s tables but an average of the
recent(?) postage costs from the seller’s address (country?) to the buyer address
(country?));
— an estimation of the shop (something with feedback, but what?).
Very unclear….
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| | | | | | | Author: | jennnifer | | Posted: | May 26, 2022 12:57 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 26 times | | Topic: | Buying | |
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| In Buying, SylvainLS writes:
| | In Buying, Bobflip writes:
| | There's a set of instructions on my wanted list, which is listed by three
sellers in the UK. They all show up in the filters, I have all the exclusions
unchecked and leave the minimum buy caveat enabled, but auto-select is selecting
the most expensive seller. The only difference I can tell is that the two cheaper
stores don't have a postage estimation, and the third store does. If I add
the most expensive one to the cart, auto-select now ignores it and it goes to
the cheapest one on the list.
So it seems the lack of a postage price is negatively affecting the results,
is there a way to disable it from being taken into account?
|
Not that we (at least I) know of.
All we (users) know (or rather, could deduce from the tidbits we were given)
is that, in the choice of Auto-select, enter:
— an estimation of the postage (not the seller’s tables but an average of the
recent(?) postage costs from the seller’s address (country?) to the buyer address
(country?));
— an estimation of the shop (something with feedback, but what?).
Very unclear….
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Does the old Wanted List give the same skewed results?
Jen
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| | | | | | | | | Author: | SylvainLS | | Posted: | May 26, 2022 13:07 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 28 times | | Topic: | Buying | |
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| In Buying, jennnifer writes:
| | […]
Does the old Wanted List give the same skewed results?
Jen
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To be clear: OP is talking about Auto-select: the automatic selection of stores
from the list of stores that can cater to your wants.
And there’s no Auto-select on the “classic” WL.
Then, AFAICT, the stores are listed in the same order on the Buy Page and the
“classic” By Shop (for the searches you can do on both, as Buy Page can do more
complex searches  ).
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| | | | | | | | | | | Author: | jennnifer | | Posted: | May 26, 2022 13:14 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 27 times | | Topic: | Buying | |
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| In Buying, SylvainLS writes:
| | In Buying, jennnifer writes:
| | […]
Does the old Wanted List give the same skewed results?
Jen
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To be clear: OP is talking about Auto-select: the automatic selection of stores
from the list of stores that can cater to your wants.
And there’s no Auto-select on the “classic” WL.
Then, AFAICT, the stores are listed in the same order on the Buy Page and the
“classic” By Shop (for the searches you can do on both, as Buy Page can do more
complex searches ).
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Got it... I am not an expert or a frequent user of either feature, but the last
time I used them, I got distinctly different results.
Jen
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| | | | | | | | | | | | | Author: | SylvainLS | | Posted: | May 26, 2022 13:26 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 24 times | | Topic: | Buying | |
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| In Buying, jennnifer writes:
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Got it... I am not an expert or a frequent user of either feature, but the last
time I used them, I got distinctly different results.
Jen
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The default filters are not the same.
But if you use the same filters and the same WL(s), they match…
…more or less because the Buy Page also sorts by store name (as a secondary sort).
At least, that’s what I see when I try.
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| | | | | | | | | | | Author: | Bobflip | | Posted: | May 26, 2022 16:14 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 28 times | | Topic: | Buying | |
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| In Buying, SylvainLS writes:
| | In Buying, jennnifer writes:
| | […]
Does the old Wanted List give the same skewed results?
Jen
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To be clear: OP is talking about Auto-select: the automatic selection of stores
from the list of stores that can cater to your wants.
And there’s no Auto-select on the “classic” WL.
Then, AFAICT, the stores are listed in the same order on the Buy Page and the
“classic” By Shop (for the searches you can do on both, as Buy Page can do more
complex searches ).
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That's it
As it stands, I can't tell if the auto-select is actually selecting the best
prices for me. I could tell in this instance as it's a rare item with a wide
range of prices across the three listed, but this could have been giving me higher
priced items for years! :-/
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| | | | | | | | | | | | | Author: | SylvainLS | | Posted: | May 26, 2022 16:49 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 29 times | | Topic: | Buying | |
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| In Buying, Bobflip writes:
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That's it
As it stands, I can't tell if the auto-select is actually selecting the best
prices for me. I could tell in this instance as it's a rare item with a wide
range of prices across the three listed, but this could have been giving me higher
priced items for years! :-/
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No one can tell. No one ever could. No one will ever be able to.¹
One reason is because some parameters are estimated (shipping), yet another is
because some parameters are qualitative (“good seller”), yet another is because
we don’t know the weight for the parameters (how is the global score calculated?),
and the last one is because, anyway, that kind of algorithm is local-optimal:
it cuts corners because it can’t test all the possibilities.
IOW, the solution isn’t “bestest price,” it’s “best composite score of price
& seller & whatever for the tested solutions, hoping best solutions weren’t eliminated
too quickly.”
So you need to test different options (like finding the rare or more expensive
parts first, prioritizing your WLs…) to see if you can give a little help to
the algorithm.
And all that hoping you won’t miss the best stores because they will only list
the parts you want tomorrow.
———
¹ Well, actually, BL could tell us: they have more info than they use and could
search longer and more optimally… but it would take more resources per buyer
than they can afford and more time per buyer than the buyer will accept, for
a meager gain to the buyer (on average).
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| | | | | | | | | | | | | | | Author: | Bobflip | | Posted: | May 26, 2022 17:54 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 26 times | | Topic: | Buying | |
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| Hmm, what bits have you read that hints at those extra parameters? The auto select
button brings up this message before you start the search:
“BrickLink will select a recommended combination of stores that can complete
your Wanted List at an optimal total price including shipping cost.”
It says “optimal total price”, there’s nothing to say that it’s taking anything
like seller rating into account, (or why it isn’t giving the optimal total price!)
Postage isn’t a consideration for me as there’s often enough other parts I need
anyway.
Though as expected it hides any stores you’ve added to your dislike list.
| | So you need to test different options (like finding the rare or more expensive
parts first, prioritizing your WLs…) to see if you can give a little help to
the algorithm.
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Ohh, I’m well into that already - I have multiple wanted lists, and this set
of instructions is in my ‘PRIORITY’ list. (I figure focussing on the rare parts
will mean the common parts will naturally come along for the ride). Heck, I even
knocked it down to searching for just this one part to track down the issue.
Before auto-select came to Bricklink, I was using that Python script from someone
on BrickSet’s forum, which only went by price, but indeed did take a long while
with some searches.
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| | | | | | | | | | | | | | | | | Author: | SylvainLS | | Posted: | May 26, 2022 19:08 | | Subject: | Re: Auto-select not prioritising cheaper item | | Viewed: | 35 times | | Topic: | Buying | |
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| In Buying, Bobflip writes:
| | Hmm, what bits have you read that hints at those extra parameters?
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Posts from admins on the forum, notably when the feature came out (the posts
don’t exist anymore) and a few others afterward (I didn’t kept links for those
ones).
So you’ll have to trust my memory 
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United Kingdom, England
France, Nouvelle-Aquitaine
USA, Illinois