Thread

Singapore govt dating app uses Gale-Shapley stable marriage algorithm

466 points · 499 comments · rzk

abeppu · 1790807528 · focus · HN ↗
So on the one hand it's nice to see when a cool algorithm or framework is used IRL.
On the other hand, actually applying a 'stable marriage algorithm' to people makes a bunch of assumptions which are worth interrogating:
- Do people actually know what they want even in the short term?
- Do people's preference change meaningfully over longer periods of time?
- Does your preference _upon reading people's profiles_ have any strong relationship to your preference after spending any amount of time with them?
The property that right after being matched, no one could have matched with someone whose profile they preferred more does not mean that this will create stable relationships.
1. miki123211 · 1790813433 · focus · HN ↗
  I think what you should be doing as a dating app — much more so if a government one — is some kind of RL based on length of actual marriage.
  At least, you should have some algorithm estimating marriage length / likelihood of divorce based on your (non-app) statistics, and then use that as one factor for your in-app calculations.
  1. pinkmuffinere · 1790817595 · focus · HN ↗
    Just to call out, you're implicitly assuming that strictly lower divorce rates is the correct end-goal. This may not be what you really want, eg you might find many abusive pairings where the weaker partner is too scared to leave. In the style of "The optimal amount of fraud is non-zero" [1], I'll claim that the optimal amount of divorce is non-zero.
    [1] <a href="https://www.bitsaboutmoney.com/archive/optimal-amount-of-fraud/" rel="nofollow">https://www.bitsaboutmoney.com/archive/optimal-amount-of-fra...
    derangedHorse · 1790824880 · focus · HN ↗
    The sentiment of the linked post is different than the one you describe. The post is explaining why it's ok to have a non-zero value for a metric seen as objectively bad (like fraud) if there's high confidence that the non-zero value can be traded for a disproportionately larger metric somewhere beneficial (user acquisition).
    In this case the undesirable metric is divorce. If the parent comment's feature for measuring marriage lengths and estimating likelihood of divorce were implemented, what disproportionate benefit would allowing more matches with a nonzero likelihood of divorce bring? The app wouldn't be enforcing whether divorces happen, it would just use the estimation of it happening as a matchmaking metric.
    pinkmuffinere · 1790829321 · focus · HN ↗
    > what disproportionate benefit would allowing more matches with a nonzero likelihood of divorce bring
    I think one benefit would be the individual participants' self-determination (there may be others). It's ok if you don't find my previous example (abusive relationship) convincing, but in the absence of an objection I'll reuse that. If we could look through all the marriages with a 0% chance of divorce, my bet is that we'd find an abnormally high percentage of abusive relationships. I claim that if a match has _no_ chance of divorce, it probably indicates a lack of self-determination for one of the partners.
    Taking a step back, it might be clearer to just argue that length / non-divorce is not what people really want from a marriage. I can't speak for everyone, but I want a happy and fulfilling life, and I seek a partnership to the extent that it supports my desire for a happy and fulfilling life. Yes, I do want the partnership to be long, and I don't want to get divorced. Of course I want my marriage to last forever. But this is not my primary goal in marriage. There are many boring or uninteresting people (apologies to them) who I'm sure I could live with forever, that I'd immediately discard as candidates. Alternatively (making the abuse angle more tangible), I also have a lot of international friends and family that would happily find me an international bride who would never divorce me, and would be happy to marry somebody with a US passport. In fact this is a somewhat common offer, though of course they never say it in those words. You can decide for yourself whether that is abuse, but at least I wouldn't feel comfortable with it.
    matrix87 · 1790831613 · focus · HN ↗
    > I also have a lot of international friends and family that would happily find me an international bride who would never divorce me, and would be happy to marry somebody with a US passport. In fact this is a somewhat common offer, though of course they never say it in those words. You can decide for yourself whether that is abuse, but at least I wouldn't feel comfortable with it.
    I'm pretty sure in this specific case, they get an instant green card if abuse happens. So the incentives point in the opposite direction (pro-divorce)
    pinkmuffinere · 1790832899 · focus · HN ↗
    That’s fair, but on the other hand they’re in a new country where they may not speak the language, and know almost nobody. To say nothing of religious/cultural views of divorce
    matrix87 · 1790833114 · focus · HN ↗
    But if the abuser can be obligated to pay legal fees, there could be incentives for lawyers to seek these kinds of cases out

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