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SBF
@SBF_FTX
Replying to
@SBF_FTX
8) So for us, 'upgrade' almost always means 'parallelization'. The core problem of matching engines is: you can always use more computers to match, but that only works if you can process in parallel. Say Alice and Bob both submit orders to buy. a & b can be done in parallel.
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SBF
@SBF_FTX
9) Risk checks are generally account specific, so you can just have a different computer handle each of theirs. But then you hit c & d: actually matching the orders. And the thing is, they're not independent. If Alice lifts an offer, Bob can't lift that same offer.
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SBF
@SBF_FTX
10) At least, not if they're in the same market. So you can't have one computer handle Alice's matching and another handle Bob's, at least not trivially, or they'll clash with each other, both thinking they lifted the same offer. This is when it gets tricky to increase capacity
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SBF
@SBF_FTX
11) e & f are somewhere in between. In some sense, f should be parallelizable: just have separate computers handle updates for each fill. But what if Bob simultaneously buys BTC/USD and BTC/USDT. Both increase his BTC balance.
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SBF
@SBF_FTX
12) If they don't talk to each other, both will report too low of a BTC balance for him! So there's still some tricky work to do there on the interplay between similar but different fills. And if you can't parallelize it, then you're stuck going one at a time.
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SBF
@SBF_FTX
13) And if you're going one by one and trading is really busy, the _single_ computer handling all fills notifications will get a bigger and bigger queue of things to notify. So at some point the real solution here has to be finding a way to do more than one at once.
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SBF
@SBF_FTX
14) (FWIW, when
@Nishad__Singh
and Gary were talking about this today, the metaphor used was basically of a symphony with a conductor, and improvements were to the conductor that coordinated which computer processed which fills.)
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SBF
@SBF_FTX
16) One missing thing from this: some of the 'clashing' when you try to parallelize things comes from updating the same single database too frequently; there's a data storage parallelization problem that mirrors the data processing one.
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SBF
@SBF_FTX
Replying to
@SBF_FTX
and
@_dwasse
but thinking about a private list of them -- my weak guess here is that if all we reported was the time/price/size/account that would be ok, but in fact we also try to keep balances/etc. updated)
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Daniel Wasserman
@_dwasse
Replying to
@SBF_FTX
and
@SBF_Alameda
I was thinking of something like this: onFill(symbol, price, size, account) { maker_balances = applyBalances(maker_account, symbol, price, size) // update db propagatePublicTrade(symbol, price, size) // trade list propagateBalanceChange(maker_balances) // balance updates }
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