{
  "id": 668810,
  "title": "Risk of overfitting to Public LB distribution",
  "url": "/competitions/csiro-biomass/discussion/668810",
  "author_name": "",
  "post_date": "2026-01-19T06:28:50.031951700Z",
  "votes": 4,
  "comment_count": 6,
  "views": 0,
  "content": "<p>I'm analyzing the recent jump in Public LB scores and it seems largely driven by post-processing rules like setting Clover to 0. While this works for the Public Test set, I doubt that the Private Test set has absolutely zero clover samples. This feels like a huge risk for a shake-up.</p>\n<p>For those aiming for a gold/silver medal, are you incorporating these public notebook strategies, or are you focusing purely on improving your model's generalization capability? I'd love to hear opinions from experienced Kagglers.</p>",
  "messages": [
    {
      "id": "3393494",
      "postDate": "01/19/2026 06:28:50",
      "content": "<p>I'm analyzing the recent jump in Public LB scores and it seems largely driven by post-processing rules like setting Clover to 0. While this works for the Public Test set, I doubt that the Private Test set has absolutely zero clover samples. This feels like a huge risk for a shake-up.</p>\n<p>For those aiming for a gold/silver medal, are you incorporating these public notebook strategies, or are you focusing purely on improving your model's generalization capability? I'd love to hear opinions from experienced Kagglers.</p>",
      "rawMarkdown": "I'm analyzing the recent jump in Public LB scores and it seems largely driven by post-processing rules like setting Clover to 0. While this works for the Public Test set, I doubt that the Private Test set has absolutely zero clover samples. This feels like a huge risk for a shake-up.\n\nFor those aiming for a gold/silver medal, are you incorporating these public notebook strategies, or are you focusing purely on improving your model's generalization capability? I'd love to hear opinions from experienced Kagglers.",
      "votes": null
    },
    {
      "id": "3393518",
      "postDate": "01/19/2026 08:05:17",
      "content": "<p>I prefer no post processing but that too isn't shake-proof. I would love if grandmasters/masters were a bit more active in sharing their experience. Like I understand no one wants to share their exact approach but atleast guide us through your experience with past competitions on tackling shakeups.</p>",
      "rawMarkdown": "I prefer no post processing but that too isn't shake-proof. I would love if grandmasters/masters were a bit more active in sharing their experience. Like I understand no one wants to share their exact approach but atleast guide us through your experience with past competitions on tackling shakeups.",
      "votes": null
    },
    {
      "id": "3393523",
      "postDate": "01/19/2026 08:22:04",
      "content": "<p>Me too. I also haven't incorporated any post processing so far. \nI would say, if one is deciding between using a post processing strategy vs not to, they should check how much improvement are they getting. If it changes the second decimal, then go for it, else not. </p>",
      "rawMarkdown": "Me too. I also haven't incorporated any post processing so far. \nI would say, if one is deciding between using a post processing strategy vs not to, they should check how much improvement are they getting. If it changes the second decimal, then go for it, else not.",
      "votes": null
    },
    {
      "id": "3393606",
      "postDate": "01/19/2026 11:54:01",
      "content": "<p>In conclusion, since you can select two Subs, you can choose one that is intentionally biased towards the target, or one that is not.</p>\n<p>As an extremely bad example, at 『NeurIPS - Open Polymer Prediction 2025』, which ended four months ago,\nA tragic incident occurred where anyone could win a <strong>Gold Medal simply by multiplying the inference result by 2: \"{PredictionResult}*2\".</strong>\nThis was because a domain shift occurred in this competition, where public was celsius and private was fahrenheit.</p>\n<p><a href=\"https://www.kaggle.com/competitions/neurips-open-polymer-prediction-2025/discussion/607769#3289402\" target=\"_blank\">https://www.kaggle.com/competitions/neurips-open-polymer-prediction-2025/discussion/607769#3289402</a></p>\n<p>Ideally, the machine learning problem setting and data division would be appropriate for Train/PublicLB/PrivateLB, but there may be competitions where this is not the case.</p>",
      "rawMarkdown": "In conclusion, since you can select two Subs, you can choose one that is intentionally biased towards the target, or one that is not.\n\nAs an extremely bad example, at 『NeurIPS - Open Polymer Prediction 2025』, which ended four months ago,\nA tragic incident occurred where anyone could win a **Gold Medal simply by multiplying the inference result by 2: \"{PredictionResult}*2\".**\nThis was because a domain shift occurred in this competition, where public was celsius and private was fahrenheit.\n\nhttps://www.kaggle.com/competitions/neurips-open-polymer-prediction-2025/discussion/607769#3289402\n\nIdeally, the machine learning problem setting and data division would be appropriate for Train/PublicLB/PrivateLB, but there may be competitions where this is not the case.",
      "votes": null
    },
    {
      "id": "3393627",
      "postDate": "01/19/2026 12:52:32",
      "content": "<p>Oh I remember the angry downvotes, lol! But the host later clarified it was just a distribution shift where everyone's models were not able to extrapolate that well (basically not very good at predicting higher values)</p>",
      "rawMarkdown": "Oh I remember the angry downvotes, lol! But the host later clarified it was just a distribution shift where everyone's models were not able to extrapolate that well (basically not very good at predicting higher values)",
      "votes": null
    },
    {
      "id": "3395597",
      "postDate": "01/23/2026 09:38:57",
      "content": "<p>I don't think there will be a big shakeup, from my personal perspective, the score on the public leaderboard for this competition is too difficult to improve, and the sample size is also considerable (800 * 53% = 424).</p>",
      "rawMarkdown": "I don't think there will be a big shakeup, from my personal perspective, the score on the public leaderboard for this competition is too difficult to improve, and the sample size is also considerable (800 * 53% = 424).",
      "votes": null
    },
    {
      "id": "3395692",
      "postDate": "01/23/2026 13:50:01",
      "content": "<p>I am working on cv mostly, but some strategies seem to be also consistant with the public leaderboard</p>",
      "rawMarkdown": "I am working on cv mostly, but some strategies seem to be also consistant with the public leaderboard",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 3393518,
      "author_name": "paritoshtripathi5",
      "author_url": "",
      "post_date": "01/19/2026 08:05:17",
      "content": "<p>I prefer no post processing but that too isn't shake-proof. I would love if grandmasters/masters were a bit more active in sharing their experience. Like I understand no one wants to share their exact approach but atleast guide us through your experience with past competitions on tackling shakeups.</p>",
      "votes": null,
      "replies": [
        {
          "id": 3393523,
          "author_name": "komilparmar",
          "author_url": "",
          "post_date": "01/19/2026 08:22:04",
          "content": "<p>Me too. I also haven't incorporated any post processing so far. \nI would say, if one is deciding between using a post processing strategy vs not to, they should check how much improvement are they getting. If it changes the second decimal, then go for it, else not. </p>",
          "votes": null,
          "replies": []
        }
      ]
    },
    {
      "id": 3393606,
      "author_name": "hideyukizushi",
      "author_url": "",
      "post_date": "01/19/2026 11:54:01",
      "content": "<p>In conclusion, since you can select two Subs, you can choose one that is intentionally biased towards the target, or one that is not.</p>\n<p>As an extremely bad example, at 『NeurIPS - Open Polymer Prediction 2025』, which ended four months ago,\nA tragic incident occurred where anyone could win a <strong>Gold Medal simply by multiplying the inference result by 2: \"{PredictionResult}*2\".</strong>\nThis was because a domain shift occurred in this competition, where public was celsius and private was fahrenheit.</p>\n<p><a href=\"https://www.kaggle.com/competitions/neurips-open-polymer-prediction-2025/discussion/607769#3289402\" target=\"_blank\">https://www.kaggle.com/competitions/neurips-open-polymer-prediction-2025/discussion/607769#3289402</a></p>\n<p>Ideally, the machine learning problem setting and data division would be appropriate for Train/PublicLB/PrivateLB, but there may be competitions where this is not the case.</p>",
      "votes": null,
      "replies": [
        {
          "id": 3393627,
          "author_name": "paritoshtripathi5",
          "author_url": "",
          "post_date": "01/19/2026 12:52:32",
          "content": "<p>Oh I remember the angry downvotes, lol! But the host later clarified it was just a distribution shift where everyone's models were not able to extrapolate that well (basically not very good at predicting higher values)</p>",
          "votes": null,
          "replies": []
        }
      ]
    },
    {
      "id": 3395597,
      "author_name": "jiazhuang",
      "author_url": "",
      "post_date": "01/23/2026 09:38:57",
      "content": "<p>I don't think there will be a big shakeup, from my personal perspective, the score on the public leaderboard for this competition is too difficult to improve, and the sample size is also considerable (800 * 53% = 424).</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 3395692,
      "author_name": "litaihao",
      "author_url": "",
      "post_date": "01/23/2026 13:50:01",
      "content": "<p>I am working on cv mostly, but some strategies seem to be also consistant with the public leaderboard</p>",
      "votes": null,
      "replies": []
    }
  ],
  "raw_markdown_by_id": {
    "3393494": "I'm analyzing the recent jump in Public LB scores and it seems largely driven by post-processing rules like setting Clover to 0. While this works for the Public Test set, I doubt that the Private Test set has absolutely zero clover samples. This feels like a huge risk for a shake-up.\n\nFor those aiming for a gold/silver medal, are you incorporating these public notebook strategies, or are you focusing purely on improving your model's generalization capability? I'd love to hear opinions from experienced Kagglers.",
    "3393518": "I prefer no post processing but that too isn't shake-proof. I would love if grandmasters/masters were a bit more active in sharing their experience. Like I understand no one wants to share their exact approach but atleast guide us through your experience with past competitions on tackling shakeups.",
    "3393523": "Me too. I also haven't incorporated any post processing so far. \nI would say, if one is deciding between using a post processing strategy vs not to, they should check how much improvement are they getting. If it changes the second decimal, then go for it, else not.",
    "3393606": "In conclusion, since you can select two Subs, you can choose one that is intentionally biased towards the target, or one that is not.\n\nAs an extremely bad example, at 『NeurIPS - Open Polymer Prediction 2025』, which ended four months ago,\nA tragic incident occurred where anyone could win a **Gold Medal simply by multiplying the inference result by 2: \"{PredictionResult}*2\".**\nThis was because a domain shift occurred in this competition, where public was celsius and private was fahrenheit.\n\nhttps://www.kaggle.com/competitions/neurips-open-polymer-prediction-2025/discussion/607769#3289402\n\nIdeally, the machine learning problem setting and data division would be appropriate for Train/PublicLB/PrivateLB, but there may be competitions where this is not the case.",
    "3393627": "Oh I remember the angry downvotes, lol! But the host later clarified it was just a distribution shift where everyone's models were not able to extrapolate that well (basically not very good at predicting higher values)",
    "3395597": "I don't think there will be a big shakeup, from my personal perspective, the score on the public leaderboard for this competition is too difficult to improve, and the sample size is also considerable (800 * 53% = 424).",
    "3395692": "I am working on cv mostly, but some strategies seem to be also consistant with the public leaderboard"
  },
  "source": "meta"
}