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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
Alhamdulillah. YB Fuziah (Kak Gee) who attended the PH - Minister Tengku Datuk Seri Utama Zafrul meeting today, informed me that MOF is keen to produce a Gender Responsive Budget (GRB) with Environmental, Social and Governance (ESG) elements for the upcoming budget. If truly realised, it would be a positive step towards addressing gender equality, and future proofing Malaysia. She also informed me that Minister DS Tengku Zafrul showed interests in MPI as a tool.
KEADILAN MPs have been working hard on these matters as part of our pre-budget preparations led by Wong Chen.
Thank you very much for the stellar work done, Ale, Wong Chen’s officer - for collating all the written suggestions and recommendations over the many pre-councils between KEADILAN MPs.
Having completed our MPI survey, led by Professor Fatimah Kari & her team, local enumerators and our ground office - culminating in a finalised report on measuring the different dimensions of poverty (six conventional & 3 COVID-19 related) in Permatang Pauh, -it brings me pleasure to have my colleagues champion a more progressive and future proof measurement of poverty & its alleviation in the upcoming Budget and 12th Malaysia Plan.
Our office finalised a few recommendations to the MOF - specifically seeking an MPI centred approach to poverty eradication; and adoption of gender responsive measures in the dispensing of our national budget. The findings through our MPI survey confirmed that women headed households are in deeper financial crisis in comparison to conventional households - with a concerning intergenerational lack of social and educational mobility and increased food poverty amongst children.
As such - our national budget must be responsive to gender - a principle that carries through to the point of implementation. Since MOF limited reps to three from each party; I urged that YB Fuziah be included together with Wong Chen and our SecGen. Kak Gee (YB Fuziah) has been a long time advocate of gender responsive budgeting and together — the three of them also stressed the need for Malaysia to achieve the SDGs - specifically the 5th, in tandem with a more realistic measurement of poverty.
As for me; the task of briefing Minister Dato’ Seri Mustapa Mohamed on our completed MPI survey & our discussion on the key highlights to be raised during our 12th Malaysia Plan RTM session tomorrow night gave me some hope - of a new dawn in poverty eradication - if not necessarily, new politics 😅 Cautiously optimistic, bak kata Uncle Wong Chen.
Much to do - waver, we mustn’t.
Please note we are planning the launch of our MPI report. Join us as the date nears #Parlimen!
【現場直播｜Live】 二零二一年度第四次評議會緊急會議｜The 4th Ordinary Ordinary Council Meeting, Session 2021
Date: 1st June 2021 (Tuesday)
Time: 19:00 –
Venue: Union Council Chamber UG201, Union Building
Section A
1. To read out the correspondences
2. To receive maiden speeches of new Council members
3. To report the motions carried by circulation
4. To receive and adopt the agenda
5. To receive and adopt the minutes of previous Meetings
Section B
1. To receive the Union President’s Address
2. Questions put to the Union Executives, other Councillors, other Official Observers,
Council Committees, or Union sub-organisations
3. To appoint chairpersons Council Committees, HKUSU Council, Session 2021
4. To appoint members of Council Committees, HKUSU Council, Session 2021
5. To appoint Acting Union Executives, Session 2021
6. To discuss disciplinary matter of the Union Council, Session 2020
7. To receive annual reports of Council Standing Committees, Session 2020
a. Current Affairs Committee, HKUSU Council, Session 2020
b. Union Finance Committee, HKUSU Council, Session 2020
c. Union Election Committee, HKUSU Council, Session 2020
8. To receive annual reports of Union Executives, Session 2020
a. President
b. Vice-President (External)
c. Financial Secretary
d. Student Welfare Secretary
e. Administrative Secretary
f. President of Cultural Association
g. President of Independent Clubs Association
h. President of Sports Association
9. To receive the annual reports of Popularly Elected Union Councillor, Session 2020
a. Popularly Elected Union Councillor I
10. To receive the annual reports of Campus Media, Session 2020
a. Campus TV, HKUSU
11. To receive the report of Council Committees ad hoc
a. Orientation Affairs Committee, HKUSU Council, Session 2020
b. Tendering Committee of Notebook Ownership Program 2020, HKUSU Council,
Session 2020
c. Tendering Committee of Union Building Shop, HKUSU Council, Session 2020
d. Annual Election Commission 2021, HKUSU Council, Session 2020
12. To discuss recommendations from the Council Business Committee
13. To discuss the affiliation status of Science Society, HKUSU
14. To endorse statements issued by Council Committees
15. Any Other Business
The Yang family have spent years in and out of hospitals with their two children Jerry and Lillian – both battling Leukemia and needing a blood stem cell transplant. Jerry was lucky enough to have a match on the Be The Match registry. Ruko donated marrow to him 5 years ago and they were able to meet for the first time!
Lillian, unfortunately, does not have any matches on the Be The Match registry and needs to find a life-saving blood stem cell donor.
Sign up today and give someone like Lillian a second chance at life.”
For information and registration, Text DanLok to 61474 or visit BeTheMatch.org/DanLok
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Dan Lok has been viewed more than 1.7+ billion times across social media for his expertise on how to achieve financial confidence. And is the author of over a dozen international bestselling books.
Dan has also been featured on FOX Business News, MSNBC, CBC, FORBES, Inc, Entrepreneur, and Business Insider.
In addition to his social media presence, Dan Lok is the founder of the Dan Lok Organization, which includes more than two dozen companies - and is a venture capitalist currently evaluating acquisitions in markets such as education, new media, and software.
Some of his companies include Closers.com, Copywriters.com, High Ticket Closers, High Income Copywriters and a dozen of other brands.
And as chairman of DRAGON 100, the world’s most exclusive advisory board, Dan Lok also seeks to provide capital to minority founders and budding entrepreneurs.
Dan Lok trains as hard in the Dojo as he negotiates in the boardroom. And thus has earned himself the name; The King of Closing.
If you want the no b.s. way to master your financial destiny, then learn from Dan. Subscribe to his channel now.
★☆★ CONNECT WITH DAN ON SOCIAL MEDIA ★☆★
YouTube: http://youtube.danlok.link
Dan Lok Blog: http://blog.danlok.link
Dan Lok Shop: https://shop.danlok.link
Facebook: http://facebook.danlok.link
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Linkedin: http://mylinkedin.danlok.link
Podcast: http://thedanlokshow.danlok.link
#BeTheMatch #Donor
Please understand that by watching Dan’s videos or enrolling in his programs does not mean you’ll get results close to what he’s been able to do (or do anything for that matter).
He’s been in business for over 20 years, and his results are not typical.
Most people who watch his videos or enroll in his programs get the “how-to” but never take action with the information. Dan is only sharing what has worked for him and his students.
Your results are dependent on many factors… including but not limited to your ability to work hard, commit yourself, and do whatever it takes.
Entering any business is going to involve a level of risk as well as massive commitment and action. If you're not willing to accept that, please DO NOT WATCH DAN’S VIDEOS OR SIGN UP FOR ONE OF HIS PROGRAMS.
This video is about Young Leukemia Survivor Meets Life-Saving Donor For The First Time (Live).
https://youtu.be/CNvguP1GB2o
https://youtu.be/CNvguP1GB2o
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Wanting to help others is a worthwhile goal - and yet you can only help one person at a time. If you want to make a true impact in this world you need to stop wasting your time and find ways to automate your help. Watch this video for Dan Lok's top tips on how to stop wasting your time and do high-impact activities instead.
? SUBSCRIBE TO DAN'S YOUTUBE CHANNEL NOW ?
https://www.youtube.com/danlok?sub_confirmation=1
? UNLOCK A Better Version Of Yourself, Check Out My Shop: https://shop.danlok.link ?
Check out these Top Trending Playlists -
1.) Boss In The Bentley - https://www.youtube.com/playlist?list=PLEmTTOfet46OWsrbWGPnPW8mvDtjge_6-
2.) Sales Tips That Get People To Buy - https://www.youtube.com/watch?v=E6Csz_hvXzw&list=PLEmTTOfet46PvAsPpWByNgUWZ5dLJd_I4
3.) Dan Lok’s Best Secrets - https://www.youtube.com/watch?v=FZNmFJUuTRs&list=PLEmTTOfet46N3NIYsBQ9wku8UBNhtT9QQ
Dan Lok has been viewed more than 1.7+ billion times across social media for his expertise on how to achieve financial confidence. And is the author of over a dozen international bestselling books.
Dan has also been featured on FOX Business News, MSNBC, CBC, FORBES, Inc, Entrepreneur, and Business Insider.
In addition to his social media presence, Dan Lok is the founder of the Dan Lok Organization, which includes more than two dozen companies - and is a venture capitalist currently evaluating acquisitions in markets such as education, new media, and software.
Some of his companies include Closers.com, Copywriters.com, High Ticket Closers, High Income Copywriters and a dozen of other brands.
And as chairman of DRAGON 100, the world’s most exclusive advisory board, Dan Lok also seeks to provide capital to minority founders and budding entrepreneurs.
Dan Lok trains as hard in the Dojo as he negotiates in the boardroom. And thus has earned himself the name; The King of Closing.
If you want the no b.s. way to master your financial destiny, then learn from Dan. Subscribe to his channel now.
★☆★ CONNECT WITH DAN ON SOCIAL MEDIA ★☆★
YouTube: http://youtube.danlok.link
Dan Lok Blog: http://blog.danlok.link
Dan Lok Shop: https://shop.danlok.link
Facebook: http://facebook.danlok.link
Instagram: http://instagram.danlok.link
Linkedin: http://mylinkedin.danlok.link
Podcast: http://thedanlokshow.danlok.link
#DanLok #StopWastingTime #Motivation
Please understand that by watching Dan’s videos or enrolling in his programs does not mean you’ll get results close to what he’s been able to do (or do anything for that matter).
He’s been in business for over 20 years, and his results are not typical.
Most people who watch his videos or enroll in his programs get the “how-to” but never take action with the information. Dan is only sharing what has worked for him and his students.
Your results are dependent on many factors… including but not limited to your ability to work hard, commit yourself, and do whatever it takes.
Entering any business is going to involve a level of risk as well as massive commitment and action. If you're not willing to accept that, please DO NOT WATCH DAN’S VIDEOS OR SIGN UP FOR ONE OF HIS PROGRAMS.
This video is about STOP WASTING TIME.
https://youtu.be/OQtwa4M9alI
https://youtu.be/OQtwa4M9alI
Everything here is MIT licensed and unsupported unless otherwise stated. Use at your own risk. - Financial Times. ... <看更多>
It is followed by an appendix describing a computer program which readers may use to help model their own financial time series. ... <看更多>
financial time 在 Financial Times - YouTube 的推薦與評價
Interested in unbiased global news and want to make sense of a changing world? The Financial Times YouTube channel showcases the best of our visual ... ... <看更多>