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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
神秘开箱啦 好像很厉害那样勒 😵
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再次感谢 AMD Corsair 的赞助 还有 Azio Online 那么体贴细心的组机给我嘻嘻🥰
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AMD Ryzen 9 5900X 12core 24thread
ASUS ROG STRIX X570E-Gaming
Sapphire Radeon RX 6700 XT Nitro+
Corsair 4000X RGB - Mid Tower ATX PC Case (Black)
Corsair Vengeance RGB PRO SL 32GB 3200MHZ (8GBx4)
Corsair iCUE H100i Elite Capellix 240MM (Black)
Corsair Force MP400 NVMe PCIe Gen3x4 M.2 SSD 2TB
Corsair RMx Series™ RM750x — 750 Watt 80 PLUS Gold Fully Modular ATX PSU
Elgato HD60S+ Capture Card
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Having a large following isn't the same as being skilled, especially in the photography scene.
In this video, I talk about Instagram and how although popularity and skill certainly can be related, it's not always the case that one reflects the other.
Support me on Patreon or join this channel to get access to exclusive perks:
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Thank you Storyblocks for sponsoring this episode. Click the link to check out Re: Stock and sign up for the Unlimited All-Access Plan: https://storyblocks.com/Kohkiyamaguchi
So here's my overall setup and what I use on a day to day photography shoot.
If I'm not shooting for YouTube, I leave my FX3 and RS2 behind.
Super curious to see what your favorite gear is so leave a comment below, maybe it will inspire me to get it :D
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My Instagram: https://www.instagram.com/Kohki
My Store: https://www.kohkipresets.com
My Website: https://www.kohkicontent.com
My Gear: https://www.amazon.com/shop/kohki
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Links to all gear in this video:
Wandrd PRVKE Backpack
https://wandrd-pacific.com/products/prvke
Stone Island Map Bag
https://www.stoneisland.com/ca/stone-island/waist-bag_cod17040736qp.html
MXDVS Accessories
https://store.mxdvs.co
DJI Ronin RS2
https://store.dji.com/jp/product/rs-2?vid=96711
Sirui Tripod
https://www.ebay.com/itm/323856166243?mkevt=1&siteid=1&mkcid=2&mkrid=21581-161791-616585-7&source_name=google&mktype=pla_ssc&campaignid=12961564719&groupid=121317197266&targeted=pla-1248581038030&MT_ID=&adpos=&device=c&googleloc=1009300&itemid=323856166243&merchantid=116792603&geo_id=104&gclid=CjwKCAjwgviIBhBkEiwA10D2j7jw75bYWSA-ONSukePdSTGWZSdawZ7xkotyipeG9KB6Q_eWXbrbSRoCIPQQAvD_BwE
Sony A7RIII
https://www.bhphotovideo.com/c/product/1645237-REG/sony_ilce7rm3a_b_alpha_a7r_iii_mirrorless.html?gclid=CjwKCAjwgviIBhBkEiwA10D2j_G68HxWqQfW0gGkb2lg8vtWUMkXZWcrjGvHRnlzvaAEeuJhBGOHERoClR8QAvD_BwE
Small Rig L bracket
https://www.smallrig.com/smallrig-l-bracket-for-sony-alpha-7-iii-alpha-7r-iii-alpha-9-camera-2122.html?sku=2122D&gclid=CjwKCAjwgviIBhBkEiwA10D2j96SkOmOEoKjMD6HBr5D_foBlaXY9KDz4hdx01YDxsz9OeYPK12vZxoCHNUQAvD_BwE
Sony FX3
https://www.bhphotovideo.com/c/product/1624226-REG/sony_ilme_fx3_fx3_cinema_camera.html
Sony GM 16-35mm f2.8
https://www.bhphotovideo.com/c/product/1338516-REG/sony_sel1635gm_fe_16_35mm_f_2_8_gm.html
Sony Zeiss 35mm f1.4
https://www.bhphotovideo.com/c/product/1126137-REG/sony_sel35f14z_distagon_t_fe_35mm.html
Sony Zeiss 55mm f1.8
https://www.bhphotovideo.com/c/product/1008124-REG/sony_sel55f18z_sonnar_t_fe_55mm.html
Sony GM 70-200mm f2.8
https://www.bhphotovideo.com/c/product/1222776-REG/sony_sel70200gm_fe_70_200mm_f_2_8_gm.html
Voigtlander 10mm f5.6
https://www.bhphotovideo.com/c/product/1219550-REG/voigtlander_ba334b_heliar_hyper_wide_10mm_f_5_6.html
Sandisk SD card
https://www.bhphotovideo.com/c/product/1617741-REG/sandisk_sdsdxdk_128g_ancin_128gb_extreme_pro_uhs_ii.html
Lexar SD card
https://www.bhphotovideo.com/c/product/1592046-REG/lexar_lsd2000128g_bnnnu_128gb_2000x_sd_uhs_ii.html
Memory Card Case
https://www.amazon.com/Beeway®-Memory-Card-Carrying-Holder/dp/B01ESSWXH2/ref=rvi_2/136-9178805-2200928?pd_rd_w=iScQp&pf_rd_p=c0296674-5a83-4ad6-b035-0702d2b359df&pf_rd_r=FCVP2SESNXTSKEQC8H4D&pd_rd_r=70488089-0360-44cf-93f8-12ec7778582b&pd_rd_wg=SUHZT&pd_rd_i=B01ESSWXH2&psc=1
Nisi Black Mist Filter
https://nisifilters.jp/product/black-mist-1-4/
Marumi Circular PL Filter
https://www.bhphotovideo.com/c/product/973423-REG/marumi_amxcpl82_82mm_exus_circular_polarizer.html
Nisi Step-Up Ring
https://nisiopticsusa.com/product/nisi-ti-pro-77-82mm-titanium-step-up-ring/
PolarPro VND Filter
https://www.bhphotovideo.com/c/product/1601822-REG/polarpro_82_2_5_vnd_ed2_pmvnd_signature_edition_ii.html?gclid=CjwKCAjwgviIBhBkEiwA10D2jy28vttAwMGno3dHq4v3dF51U0h5EiJkGu1RWkCXWNEFrbkiLa_W_RoCUwwQAvD_BwE
TYCKA Filter Pouch
https://www.amazon.com/TYCKA-Removable-Water-Resistant-Dustproof-Adjustable/dp/B07T8HTR17
Giottos Rocket Dust Blower
https://www.bhphotovideo.com/c/product/318545-REG/Giottos_AA1910_Rocket_Air_Blower.html
Aputure Light
https://www.bhphotovideo.com/c/product/1268206-REG/aputure_al_m9_amaran_pocket_sized_led.html?gclid=CjwKCAjwgviIBhBkEiwA10D2j339QH7ED6Pd9Y-9WAdroazmIiQNX4_hSbjPs-H840RhyOQW-4M3RRoCGnUQAvD_BwE
LensSkirt Lens cover
https://lenskirt.com/lenskirt/
Anker Battery Bank
https://us.anker.com/collections/portable-power/products/a1263
*I do NOT receive any commission from these links.
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Chapters:
0:00 Intro
0:39 Camera Bag
1:58 Small essentials
2:30 Messenger Bag
3:11 Gimbal / Tripod
3:46 Cameras
4:46 Lenses
8:35 AD
9:47 Batteries
10:23 SD cards
11:04 Filters
13:10 Accessories
14:49 End
#WhatsInMyCameraBag
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