【DJ電競 X ahq】A的意志？！BYG難逃與老對手EDG、TI同組的命運！

S11入圍賽將於10/5號熱血開打，就分組結果來看，A組HLE、LNG沒有懸念，而B組，BYG、C9跟有三個韓國人的DFM將是三搶二的激烈競爭。

按照A的意志卦象，將是HLE、LNG、C9、BYG晉級小組賽，根據賽制，同賽區不能同組，所以HLE只能去C組、LNG只能去D組，這樣C9剩A組能去，最後BYG就剩有EDG跟T1的B組了，只能說PCS第二種子，命運安排就是如此。

當然，除非C9沒進，BYG才有去A組的可能，但A組有DK、FPX…..，看起來也是輸贏都精彩了! 最後BYG將是2-4或是3-3飲恨小組賽。

這次在開賽前，A的意志就來當神預測一番：
入圍賽：
A組：HLE、LNG
B組：BYG、C9

小組賽：
8強：
A組：DK、FPX
B組：EDG、T1
C組：RNG、PSG(PCS賽區，要歐硬)
D組：MAD、GEN.G

四強：
DK、EDG、FPX、GEN.G

冠亞軍：
DK、EDG

冠軍：
EDG

服氣嗎? 不服就歡迎來
DJ電競Discord頻道：https://discord.gg/djesportsx 大膽留言賺DJT幣
再到DJ電競官網平台：https://djesports.io 參加競猜大賽囉!

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📜 [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

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サウンド利用許可証
魔王魂で公開されているサウンドをYouTubeで利用することを全ユーザーに対して許可します。
魔王魂の音楽素材を使用・編集加工・演奏することを許可します。
著作を偽って使用することは出来ません。（自分が作った曲と言い張ることです）
魔王魂の素材を利用したことによって生じた損害には魔王魂は一切関与しません。
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（例 音楽：音楽素材/魔王魂 ご不明な点があればお問い合わせ下さい。

Riot Games Legal：https://www.riotgames.com/en/legal
Ad Revenue：We permit individual players to promote their Projects on websites, streams, or videos and passively generate revenue through appropriate advertisements, including pre-roll ads, ad breaks, and sponsor ad overlays. No inappropriate ads—we alone decide what qualifies as inappropriate.

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信星科技 飛智銀狐X1【超低延遲】
遊戲音樂藍牙耳機
.......................
與RNG職業戰隊優化了它
聽聲辨位和腳步聲的強化

充電10分鐘 戰鬥2小時
50ms 超低延遲

30H 高續航
13.4mm 大動圈
PU 複合鍍鈦振膜
121db 高靈敏 高音質
ENC 通話降噪

職業戰隊的推薦
熱愛玩手遊的你
還缺一副好耳機
就在這▼官方網▼
https://www.flydigi.tw/product/detail/902575
折扣碼：FDG1（折抵100元）
臺灣公司貨，享有臺灣保固一年！