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在 straightforward產品中有321篇Facebook貼文，粉絲數超過3,460的網紅Taipei Ethereum Meetup，也在其Facebook貼文中提到， 📜 [專欄新文章] Gas Efficient Card Drawing in Solidity ✍️ Ping Chen 📥 歡迎投稿： https://medium.com/taipei-ethereum-meetup #徵技術分享文 #使用心得 #教學文 #medium Assign r...

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straightforward 在 A PASSIONATE FOODIE Instagram 的最佳解答

2021-09-22 09:05:22

Having withstood two postponements due to the lockdowns, I was beside myself with joy when I finally arrived at the familiar nondescript entrance shoe...

  • Taipei Ethereum Meetup

    straightforward 在 Taipei Ethereum Meetup Facebook 的精選貼文

    2021-09-23 21:53:53
    有 6 人按讚

    📜 [專欄新文章] Gas Efficient Card Drawing in Solidity

    ✍️ Ping Chen

    📥 歡迎投稿： https://medium.com/taipei-ethereum-meetup #徵技術分享文 #使用心得 #教學文 #medium

    Assign random numbers as the index of newly minted NFTs

    Scenario

    The fun of generative art NFT projects depends on randomness. The industry standard is “blind box”, where both the images’ serial number and the NFTs’ index are predetermined but will be shifted randomly when the selling period ends. (They call it “reveal”) This approach effectively solves the randomness issue. However, it also requires buyers to wait until the campaign terminates. What if buyers want to know the exact card right away? We’ll need a reliable onchain card drawing solution.

    The creator of Astrogator🐊 isn’t a fan of blind boxes; instead, it thinks unpacking cards right after purchase is more interesting.

    Spec

    When initializing this NFT contract, the creator will determine the total supply of it. And there will be an iterable function that is randomly picking a number from the remaining pool. The number must be in range and must not collide with any existing ones.

    Our top priority is accessibility/gas efficiency. Given that gas cost on Ethereum is damn high nowadays, we need an elegant algorithm to control gas expanse at an acceptable range.

    Achieving robust randomness isn’t the primary goal here. We assume there’s no strong financial incentive to cheat, so the RNG isn’t specified. Implementers can bring their own source of randomness that they think is good enough.

    Implementation

    Overview

    The implementation is pretty short and straightforward. Imagine there’s an array that contains all remaining(unsold) cards. When drawIndex() is called, it generates a (uniform) random seed to draw a card from the array, shortens the array, and returns the selected card.

    Algorithm

    Drawing X cards from a deck with the same X amount of cards is equal to shuffling the deck and dealing them sequentially. It’s not a surprise that our algorithm is similar to random shuffling, and the only difference is turning that classic algo into an interactive version.

    A typical random shuffle looks like this: for an array with N elements, you randomly pick a number i in (0,N), swap array[0] and array[i], then choose another number i in (1,N), swap array[1] and array[i], and so on. Eventually, you’ll get a mathematically random array in O(N) time.

    So, the concept of our random card dealing is the same. When a user mints a new card, the smart contract picks a number in the array as NFT index, then grabs a number from the tail to fill the vacancy, in order to keep the array continuous.

    Tweak

    Furthermore, as long as the space of the NFT index is known, we don’t need to declare/initialize an array(which is super gas-intensive). Instead, assume there’s such an array that the n-th element is n, we don’t actually initialize it (so it is an array only contains “0”) until the rule is broken.

    For the convenience of explanation, let’s call that mapping cache. If cache[i] is empty, it should be interpreted as i instead of 0. On the other hand, when a number is chosen and used, we’ll need to fill it up with another unused number. An intuitive method is to pick a number from the end of the array, since the length of the array is going to decrease by 1.

    By doing so, the gas cost in the worst-case scenario is bound to be constant.

    Performance and limitation

    Comparing with the normal ascending index NFT minting, our random NFT implementation requires two extra SSTORE and one extra SLOAD, which cost 12600 ~ 27600 (5000+20000+2600) excess gas per token minted.

    Theoretically, any instantly generated onchain random number is vulnerable. We can restrict contract interaction to mitigate risk. The mitigation is far from perfect, but it is the tradeoff that we have to accept.

    ping.eth

    Gas Efficient Card Drawing in Solidity was originally published in Taipei Ethereum Meetup on Medium, where people are continuing the conversation by highlighting and responding to this story.

    👏 歡迎轉載分享鼓掌

  • straightforward 在 Facebook 的最讚貼文

    2021-09-01 11:41:14
    有 2,823 人按讚

    Di tarik balik!
    .
    Disebabkan lambat ke call room dan selepas pertandingan dan lepas pecahkan rekod dunia barulah di protes oleh peserta lain.itulah situasi yg berlaku kpd abang ‘badang’ kita ni.
    .
    So kesannya kita kehilangan pingat emas dan sya pasti new world record pun tidak sah lah.ape perasaan @ziyadzolkefli and the whole team kan?
    .
    So, apakah lesson learn yg kita dpt? Dlm sukan komitment n disiplin sgtlah penting. Sya sebagai bekas atlet (pemain bola sepak) dan juga pernah mewakili negara. Disiplin n komitment amatlah penting.kita semua belum pasti apakah punca yg membuatkan @ziyadzolkefli lewat ke call room.tetapi undang2 pertandingan ni ‘buta’ n very straightforward. No excuse!
    .
    Persolannya, dimanakah pegawai atau team yg bersama @ziyadzolkefli ketika itu? Apa2 pun kita tggu jawapan rasmi dari kontijen Malaysia utk paralympic ni.
    .
    Tidak perlulah kita persalahkan pihak penganjur diatas penarikan balik pingat emas ni kerana jelas dan nyata yg kita melanggar undang2 pertandingan.
    .
    Bro @ziyadzolkefli ,tahniah sya ucapkan dan seluruh rakyat Malaysia bangga dgn awk, satu dunia tahu awk adalah pemegang rekod baru dunia. Jangan rasa down n keep it up.more to come bro! Pasti ade hikmah disebalik semua ni.
    .
    #paralympics
    #ziyadzolkefli
    #newworldrecord

  • Victor Chau Yoga

    straightforward 在 Victor Chau Yoga Facebook 的精選貼文

    2021-08-25 21:04:15
    有 1 人按讚

    SIMPLE DOES IT.

    If you think the most complicated problem requires the most complex solutions, think again. Sometimes the biggest challenges in life or yoga poses requires the simplest solution, alignment or tool. A #yogawheel here helps me achieve this #halflotus #hollowback #inversion. Without the wheel, this pose will be nearly impossible.

    We often look for answers in all the wrong places, making things unnecessarily complicated. If you think you’re poor, you’d think making money will make you happy. Or if you’re a yoga teacher, you might think teaching the most challenging poses or having the most beautiful Instagram will make you a great yoga teacher.

    Try to think of the most straightforward and simple things that you can do next time you face a challenge. If you feel stuck in a rut, take a deep breath, close your eyes, meditate a little. The answer you’re looking for can be super simple or next to you.

    Got a similar experience you want to share? Let me know in comments below :)

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