特別節目·中文精讀

弗拉基米爾·萬普尼克:統計學習

Vladimir Vapnik: Statistical Learning

統計學習理論奠基人回顧支援向量機與VC理論的來路,並探討機器學習的本質。

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2018 年秋天,萬普尼克(Vladimir Vapnik)在 Lex Fridman 的播客裡留了一道題。

MNIST 手寫數字識別,深度學習用六萬個訓練樣本,把準確率做到 99.5%。萬普尼克說,你能不能只用六百分之一的樣本,做到同樣的事?

條件是把不變性放進去。

這道題他放在演講的最後一頁,講完就下臺了。到今天,接的人也不多。

萬普尼克是統計學習理論的主要建立者。VC 維裡的那兩個字母,V 和 C,其中一個就是他。支援向量機(SVM)、支援向量聚類,也都是他和團隊做出來的。1936 年生於蘇聯,在莫斯科控制科學研究所工作多年,後來去了美國,在 AT&T 實驗室、Facebook 研究部門待過,現在是哥倫比亞大學教授。論文被引用超過十七萬次。

這場對話裡,他幾乎把當下最熱的東西挨個批了一遍,但批得很講道理。

上帝擲不擲骰子,取決於你站在哪一邊

Lex 用愛因斯坦那句“上帝不擲骰子”開場,問他:你一輩子用統計的眼光看世界,那上帝到底擲不擲骰子?

萬普尼克的回答很平:“你有一些不知道的事實。因為有些可能很重要的因素你不知道,看起來就像上帝在擲骰子。”

然後他把話題拐到了哲學裡的兩個位置:工具主義(instrumentalism)和實在主義(realism)。工具主義造的是能用來預測的規則,實在主義想搞清楚你描述的那個東西到底是什麼。

他舉了個例子。你寫下一組力學定律,這組定律是什麼?是上帝定下的、處處成立的法則,還是一個能讓你算出物體下一刻位置的公式?你相信前者,你就是實在主義者;你只在乎後者,你就是工具主義者。

如果你相信這是上帝的法則,那它處處都成立。這意味著你在追求真正理解。如果你只想預測,那你看到的世界就完全是另一個樣子。(萬普尼克)

這個區分聽著抽象,其實是整場對話的地基。後面他批評深度學習、批評理論電腦科學、批評人工智慧這個詞本身,用的都是這把尺子。

機器學習的目標,被寫錯了

萬普尼克說,現在所有人做機器學習,目標函式都寫成分類準確率。這是工具主義的選擇。

從工具主義的角度看,兩條路都能走通,大家也都這麼幹,因為機器學習的目標就是預測。這沒錯,它是一個預測工具。但機器學習的真目標,是學出條件機率。(萬普尼克)

他接著說得很直接:我不需要知道某個具體情況下機率是多少,我只要一條規則,一條能做預測的規則。可要理解,就必須有條件機率。

這話聽著像文字遊戲,實際上是在劃一條線。一條規則只告訴你答案,條件機率告訴你這個世界在這一點上長什麼樣。前者能刷榜,後者能遷移。

這個區別在工程上非常具體。一個只學了決策邊界的模型,換一批資料分佈就崩;一個學到了條件機率結構的模型,換環境還能撐住。過去十年,工業界反覆在這件事上吃虧,吃了又忘,忘了再吃。

數學是上帝的語言,但人得先閉嘴

Lex 提到維格納(Eugene Wigner)1960 年那篇《數學在自然科學中不合理的有效性》。萬普尼克說,他信這個說法。

數學家去找那些神奇的結構,他們知道關於現實的某些東西。做自然科學的人盯著一個方程,想從中理解現實。同樣的邏輯,如果你非常小心地看那些定義條件機率的方程,你能從中理解到的現實,比從自己的幻想裡得到的多得多。(萬普尼克)

他還說了一句挺重的話:人類的直覺很貧乏,很原始,看不見那些簡單的情形。

那人類最好的東西是什麼?他的答案是公理。“人類最好的創造是公理,剩下的是技術活,看公理把你帶到哪裡去。”

Lex 追問,愛因斯坦發現狹義相對論的時候,想象力難道沒起作用?萬普尼克的回答不太留情面:那些像“特徵”一樣的想象,深度學習那種方式的想象,跟問題本身沒關係。你從方程出發一步步推,推出來的簡單理論遠遠超出任何人能想象的東西。想象只是解釋,解釋只是幻想。

他舉了自己工作裡的一個例子。一步步解方程,做著做著冒出來一項,想了半天才明白,它描述的是觀察點的位置,也就是你把大量資訊丟掉的那個位置。人不看觀察點的組成,人只看殘差。這個想法簡單,可從方程裡推出來,比拍腦袋想到要可靠得多。

顯微鏡下的國王與王后

列文虎克(Antonie van Leeuwenhoek)第一次用顯微鏡看血液。他看到了紅細胞,然後寫報告寄到倫敦的皇家學會,說這是國王和王后的軍隊在打仗。

他看對了,但他給的解讀是錯的。(萬普尼克)

這段話的分量在於後半句。萬普尼克說,人腦也可能是這樣。我們觀察到的現象是真的,我們給它的解釋可能是自己編的。而且編得越生動,別人越容易信。

把這個故事套到今天的 AI 討論上,你會發現它每天都在重演。有人看到模型能做某件事,就編一套“它在推理”“它在理解”的故事;有人看到模型做錯了,就編一套“它缺少世界模型”的故事。觀察是清晰的,解釋是編的。區別只在於,列文虎克至少把顯微鏡借給了別人看。

“像蝴蝶一樣彈”到底傳遞了什麼資訊

萬普尼克提到一句老話:跟一位好老師學一天,勝過自己苦學一千天。他問,從數學上看,一位好老師到底做了什麼?

沒幾個人知道答案。這就是智慧。可是從歷史上、從大規模機器學習的實踐裡,我們知道老師能做的事很多。(萬普尼克)

他的猜想是,老師提供的是謂詞(predicate)和不變數(invariant)。老師知道現實長什麼樣,能把現實的形態描述出來。一旦你手裡有了不變數,需要的觀測數量可以降一百倍。

Lex 舉了個例子:鋼琴老師跟學生說,“像蝴蝶一樣彈”。這句話裡到底裝了什麼資訊?語言本身好像根本沒包含這些東西。

萬普尼克的回答是,他相信那是一個謂詞,只是他還不知道它具體是什麼。“這正是智慧和機器學習該乾的事,剩下的都是數學技術。”

Lex 說他彈了很多年吉他,這句話確實有東西在傳遞。萬普尼克順著說下去:最近發現,學習有兩種收斂機制。一種是以前大家一直在用的,另一種是強收斂,它可以吃謂詞。你說出“像蝴蝶一樣”,學生的彈法立刻就變了。資訊是即時生效的。

他還有一句話很值得記下來:每一個謂詞都是為了讓可容許集變小而發明的。

會游泳的鴨子和不會下棋的鴨子

“如果它看起來像鴨子,遊起來像鴨子,叫起來像鴨子,那它大概是隻鴨子。”

萬普尼克說這句話精確得嚇人。三個謂詞:看起來像鴨子、遊起來像鴨子、叫起來像鴨子。每一個都是合法謂詞。

他也完全可以說“跳起來像鴨子”。這個謂詞一樣合法,一樣語法正確,可它一點用都沒有,因為鴨子、鳥、動物之間在跳躍這件事上沒什麼區別,它不提供任何資訊。

那麼問題來了:怎麼判斷一個謂詞有沒有用?

到目前為止,現有的機器根本不用謂詞。你給工業界幾十億條資料,他們大概也只用三個謂詞。(萬普尼克)

機制是這樣的。你手上有海量候選函式,訓練資料告訴你“鴨子應該長這樣”,於是你砍掉所有不長這樣的函式,集合小了一圈。第二個謂詞進來,再砍掉一批。幾輪下來,剩下的函式不多了,從裡面挑表現最好的那個。

這就是謂詞在數學上的全部功能:縮小可容許函式集(admissible set of functions)。

這件事解釋了為什麼人不需要那麼多例子。你只見過幾只鴨子,就能認出鴨子,因為別人早就把“遊起來像鴨子”“叫起來像鴨子”這兩個謂詞塞給你了,你只需要很少的樣本去完成最後的挑選。

學習問題裡最難的一半,被教科書劃掉了

到這裡,VC 維該出場了。

Lex 請他向外行解釋 VC 維。萬普尼克說,你可以把它想成從一個可容許函式集裡挑出函式的能力。這個集合可以很大,大到包含所有連續函式,那它就廢了,你根本沒有那麼多樣本去挑。它也可以很小,小到裡面的函式彼此差別不大。他說他更願意把這個性質叫“多樣性”(diversity),而不是“容量”。

目標是把一個 VC 維小、又包含好函式的可容許集造出來,然後用很少的觀測把那個函式挑出來。這就是學習的任務。(萬普尼克)

接下來是整場對話裡最鋒利的一句。

經典統計學習理論裡,可容許函式集是給定的。每本教科書都這麼寫。可造出這個集合,恰恰是整個問題裡最難的那部分,它被排除在討論之外了。(萬普尼克)

這句話值得停下來想一會兒。一百年來,統計學習理論在給定的函式集裡把誤差界算得漂亮至極,可工程上真正決定成敗的那一步,是怎麼設計這個集合。所有做特徵工程、做架構設計、做歸納偏置的人,乾的都是這一步,而這一步在理論裡是空的。

具體怎麼造?靠不變數。你算出函式在訓練資料上的平均值,再算出它在模型上的期望,兩者應該相等。這種約束不針對某一個函式,它要求集合裡所有函式都滿足。這就是他說的強收斂機制。傳統統計學習用的是另一套東西,一致大數定律(uniform law of large numbers)。他特意強調,這兩者差別巨大。

差別在資訊量上。一個樣本能提供超過一 bit 的資訊,因為你說“這是 2”,等於砍掉了一半候選函式。而一個謂詞能砍掉的遠不止一半。從形式上看,“看起來像鴨子”這句話攜帶的位元數,大到無法從樣本里統計出來。

他對深度學習的評價很不客氣

萬普尼克講了個丘吉爾的例子。丘吉爾寫二戰史,開頭描述舊時代的規矩:戰爭結束,各位君王聚在一起,他們幾乎全是親戚,坐下來商量怎麼建立和平,最後能達成協議。一戰不一樣,普通公眾上了臺,貪婪壓過一切,所有人都看得出來這不是和平,和平只能維持二十年,因為坐在談判桌前的不是專業人士。

他說,華盛頓的數學家看問題看得很深。而電腦科學家大多不懂數學。

他們發明了一堆 bla bla bla 的解釋,比如深度學習。為什麼它有效?他們不知道。做深度學習的人不懂數學,也不懂神經元。它就是一堆函式。你願意的話,叫它分段線性函式,那就在分段線性函式的類裡做。可他們發明了一些詞,然後用這些解釋去論證優勢,而這些解釋大多是錯的。最後他們去搬大腦,而沒有人知道大腦裡到底在發生什麼。(萬普尼克)

他提到一個叫“代表性”(representativity)的結果,說學習問題的最優解落在淺層網路裡,不在深層網路裡。這個說法在圈內爭議很大,但它是從定理裡出來的,不是從情緒裡出來的。

Lex 試著往回拉:你不覺得這件事本身很美嗎?它居然真的跑通了。

萬普尼克說,你說的美是解釋的美。他補了一句很清醒的話:深度學習好用這件事本身沒錯,問題在於它用的訓練資料是幾十億條。人類不需要這麼多。

AlphaGo 不是一個難題

Lex 問的是 AlphaGo。用神經網路估計棋盤價值、估計落子機率,贏下人類最強棋手,這件事不讓你驚訝嗎?

萬普尼克說,“你的解釋是估計質量。是的。”然後補了一句:“這不是一個很難的問題。”

Lex 說,那我們只是經驗上發現它不難。萬普尼克說:“對,我沒法反駁你。”

這段對話很短,但他其實是在說一個方法論上的事。圍棋被人類當成智力的高峰,很大程度上是因為人類自己在棋盤上投入了幾千年,訓練出了一套精巧的直覺。機器繞過了這套直覺,用的是另一種東西。機器贏棋這件事證明不了它有多聰明,只說明人類給圍棋加了不少神秘感,而機器沒買這個賬。

他自己也承認,這套判斷沒法拿到實證。所以他把話收在了一個可操作的地方:深度學習能做的事,用一百倍更少的樣本也能做,只要你有好的不變數。這是可以驗證的,那就去驗證。

智慧也許不全在顱骨裡面

Lex 提到了圖靈。圖靈在 50 年代那篇論文裡,其實完全清楚模仿遊戲不等於思考。他心裡明白得很,可他故意把問題換成了模仿問題。換完之後,這問題就有了可操作性。

萬普尼克說,他不確定智慧只在我們內部。他舉了一個觀察:非歐幾何在 19 世紀被好幾個人幾乎同時搞出來,羅巴切夫斯基、鮑耶、高斯,前後差了十年左右。類似的事在科學史上反覆出現,總有一個十年左右的視窗,不同地方的人獨立做出同一個東西。

所以也許我們把智慧當成只存在於內部的模型是錯的。這是我們的解釋。也許它跟某種世界層面的智慧有連線,我不知道。(萬普尼克)

Lex 順著說,你像是在插線,往一個大網路裡貢獻節點。萬普尼克說:“對,就是這樣。”

這段話聽起來玄,但放在他整場的立場裡其實很一致。他一直在說:我們的解釋可能是錯的,可能是我們自己編的故事。把智慧框在顱骨裡,也是一種解釋。

最壞情況和最好情況能描述,中間不行

Lex 問他對 P 與 NP 和計算複雜度的看法。萬普尼克說這問題有意思,然後講了另一件事。

1990 年前後,一批蘇聯學者到了美國。他說這些人既不懂統計,也不懂這個領域的歷史。當時蘇聯已經出了兩本專著,美國人不知道,等於重新學了一遍。有人告訴他,這批人會從最壞情況入手,會搞出一團混亂。

“但至今也沒有。因為更合邏輯的做法是:你只能做你的數學允許你做的事,前提是這件事有清晰的理解和清晰的描述。複雜度理論就是沿著這條線引入的。”

接著是那句關鍵的話:最壞情況和最好情況都能寫成一般的形式,中間那一段不行。

你沒法描述中間的情形,因為它不夠一般。你只能描述邊界,邊界很清楚,可以建模。可你不可能為每一個新情況建一個模型。(萬普尼克)

Lex 用了個挺妙的類比:這就像用一個人一輩子幹過最壞的事和最好的事來評價他,中間那些全不算。萬普尼克沒完全接受這個類比。在他看來,中間那些同樣重要,只是沒法一般化地描述。你能描述的是極端,極端有結構,中間沒有。

這話對做工程的人其實很有用。你評估一個系統,最壞延遲和最好效能都能測、都能算、都能寫進 SLA。可真實世界的表現落在中間,而那一段你只能用統計去看,統計又需要大量樣本,樣本又貴。整個迴圈就卡在這裡。

二十年前,沒人信

90 年代中期,萬普尼克和團隊提出支援向量機。他記得很清楚:“當時除了一個人,沒人相信。”

二十年後,它成了時尚。核方法、SVM,到處都是。

Lex 問,你做這件事的時候,有沒有一種“這東西是對的”的感覺?萬普尼克說,有。“我們立刻就認出來,它會一直留下來。”

然後他說,這次的不變性理論,感覺一模一樣。

因為我有證明,不存在另外的機制。你能做的只是一些表面上的改進。可把不變性和統計學習放在一起,你還能把“智慧是什麼”給形式化出來,並且把它和技術部分分開。(萬普尼克)

這是他整場最自信的一句話,也是最需要被檢驗的一句話。一個理論家說出“我證明了不存在另外的機制”,通常意味著他把某種框架的邊界畫得很死。歷史上這類斷言有對有錯,所以真正值得看的,是他給出的那條可驗證的挑戰:MNIST,六百分之一的樣本,把不變性放進去。

他做研究時最快樂的時刻

Lex 問,回頭看,作為研究者最快樂的時刻是什麼?他特意限定了一句:別談對社會的衝擊,只說那天你心裡有多爽。

萬普尼克說,每次你搞明白一點東西的時候。然後他說了一段很樸素的話。

大部分時間我都是錯的。你得一遍又一遍地回去,對自己誠實。別急著解釋,別搞出一堆 bla bla bla,試著弄清楚這件事跟 ground truth 到底有沒有關係。(萬普尼克)

Lex 問,那你允許自己為“可能發現點什麼”而興奮嗎?他說允許,但必須反覆檢查。跟 ground truth 有關的興奮是暫時的,你得再驗證一次。

關於詩和音樂,他說 ground truth 到處都能看到。哲學家有時候說得很深,有時候完全跑題。音樂裡也有 ground truth,是結構。古典的、清晰的、簡單的結構。你看著它,跟看一組公理展開成一個理論時的感覺是一樣的。

這段大概是整場最不像技術討論的部分,但它其實解釋了萬普尼克為什麼一直對“解釋”這麼警惕。他見過真正的結構長什麼樣,所以對仿製品格外敏感。

他留下的兩個開放問題

第一個問題:為什麼一位老師比另一位老師好?

這件事跟教育學沒關係。他把這件事拆得很細:老師說的話裡,有些是在重複課本上的內容,有些是隨口的評論,有些是他自己對這門學問的哲學。到底哪一部分起了作用?如果一位老師只會說“像鴨子一樣跳”,他提供的資訊量是零。如果他說“像鴨子一樣遊”,資訊量可能很大。判斷這兩者的差別,就是判斷謂詞的好壞。而判斷謂詞的好壞,就是智慧本身。

人們甚至還沒開始理解智慧。要理解智慧,第一件事是理解老師到底做了什麼。(萬普尼克)

第二個問題,就是開頭那道題。他自己給了思路:給數字加上對稱性的謂詞,水平對稱、垂直對稱、對角對稱,還可以有別的東西,比如整幅圖的明暗程度。這些謂詞一層層往上加,可容許集一層層縮小,需要的樣本數量就一層層下降。

Lex 反問了一個很實在的問題:要區分 2 和 3,我好像得先有十幾年的童年。跟小孩玩、上學、被父母吼、走路、跳、看鴨子,然後才能生成正確的謂詞。

萬普尼克說了一句很硬的話:“我很確定,你必須知道一些比數字更多的東西。”

也許是幾種描述語言,也就是數字的組成元素。我在說對稱性,說幾何性質,說一些抽象的東西。我還不知道那是什麼。這就是智慧問題。(萬普尼克)

所以他把整個領域切成了兩半。一半是統計的,只要你把謂詞交給我,我就能用很少的樣本把活幹完,這部分已經準備好了。另一半是造謂詞的,沒有人知道怎麼做,甚至沒有人正式把它當成一個問題提出來。

過去十年,整個行業把資源幾乎全壓在前一半上。後一半被叫做“特徵工程”,然後被大規模預訓練和 Scaling Law 糊過去了。萬普尼克在 2018 年說這件事的時候,語氣是有點孤獨的。

可以立刻用起來的幾件事

  • 模型效果不好時,先別急著加資料。問一句:這個問題裡有什麼不變數?對稱性、守恆量、單調性、某種等價關係,任何能砍掉一半候選假設的東西,都比十萬條新樣本值錢。
  • 把自己的任務寫清楚:你要的是規則,還是條件機率?要規則就去做分類器,要理解就去建模分佈。這兩個答案指向完全不同的技術路線,混著做是最常見的失敗來源。
  • 用一個具體的標準檢驗你的特徵:這個特徵能不能讓候選假設集顯著變小?如果不能,它就是在說“跳起來像鴨子”,語法正確,資訊量為零。
  • 每寫一段對模型行為的解釋,回頭檢查一次:這是觀察,還是故事?列文虎克看見了紅細胞,這件事是真的;國王和王后打仗,那是他編的。
  • 評估系統時,最壞情況和最好情況都能量化,中間那段不能。別拿邊界上的漂亮數字去承諾平均表現,那一段只能靠統計,統計需要樣本,樣本要花錢。
  • 遇到一個熱門概念,做一次翻譯練習:把所有解釋性的詞去掉,剩下的數學是什麼?如果剩下的是“分段線性函式”,那就用分段線性函式的語言去討論它。
  • 找一件你長期做錯的事,像萬普尼克說的那樣,一遍又一遍地回去。對自己誠實的意思是:不給自己編一個聽起來合理的解釋就收工。
文稿由本站用語音識別模型(基於官方釋出音訊)機器轉寫,可能有識別錯誤,人名與數字請以音訊為準。
[00:00:00] The following is a conversation with Vladimir APNIC, he's the convention support vector machines, support vector clustering, VXI theory and many foundational ideas and statistical learning. He was born in the Soviet Union and worked at the Institute of Control Sciences in Moscow, then in the United States. He worked at AT&T Labs Facebook Research and now is a professor at Columbia University. His work has been cited over one hundred seventy thousand times, he has some very interesting ideas about artificial intelligence and the nature of learning, especially on the limits of our current approaches and the open problems in the field. [00:00:40] This conversation is part of an MIT course on artificial general intelligence and the artificial intelligence podcast. If you enjoy it, please subscribe on YouTube or read it on iTunes or a podcast provider of choice, or simply connect with me on Twitter or other social networks at Lex Friedman spelled F Outride. And now here's my conversation with Vladimir, Bartnick. Einstein famously said that God doesn't play dice. Yeah, you have studied the world through the eyes of statistics. So let me ask you, in terms of the nature of reality, fundamental nature of reality, does God play dice? [00:01:36] You don't know some facts, and because you don't know some factors which could be important, it looks like go play those. But what you should describe in philosophy is they distinguish between two positions, positions of instrumentalism where you're creating suited for production. And position of realism, where you're trying to understand what did you describe instrumentalism and realism a little bit. [00:02:13] For example, if you have some mechanical logs, what is that? Is it law which through AlwaysOn everywhere or it is law which allow you to predict position of moving element. What you believe, you believe that it is God's law that God created the world, which would be to this physical law, or it is just lawful predictions, and which one is instrumentalism for predictions? [00:02:54] If you believe that this is a law of God, it isn't always true everywhere. That means that you're the oldest. So you're trying to really understand, understand that God sort say the way you see the world as an instrumentalist. [00:03:15] You know, I was working for some models model of machine learning, so in this model we can see setting. And we try to solve resolve the setting to solve the problem, and you can do it in two different ways from the point of view of instrumentalise, and that's what everybody does not because this is a goal of machine learning, is to point zero for classification. That is true, but it is an instrument for prediction. But they can see the ghost of machine learning is to to learn about conditional probability. [00:04:05] So I have got to use and he is Hipsley, what is probability for one, what is probability for a given situation, but for prediction? I don't need this. I need the rule but for understanding need conditional probability. [00:04:23] So let me just step back a little bit first to talk about you mentioned, which I read last night, the the parts of the 1960 paper by Eugene Wigner are unreasonable effectiveness of mathematics and natural sciences. [00:04:39] There's a such a beautiful paper, by the way, you made me feel. [00:04:46] To be honest, to confess my own work in the past few years on deep learning, heavily applied, made me feel that I was missing out on some of the beauty of nature in the way that math can uncover. [00:05:00] So let me just step away from the poetry of that for a second. How do you see the role of math in your life? [00:05:08] Is it is it a tool or the poetry? Where does it sit? And does math for you have limits of what it can describe? Some people saying that Moss is language which use God. [00:05:23] So I believe if I speak to God or use God or use God. Yeah. So I believe that. This article. About effectiveness, unreasonable effectiveness as much is that if you're looking in which magical structures? They know something about reality. And the most. Scientists from natural science, they're looking at an equation in trying to understand reality. So the same emotional logic, if you drive very carefully, look on all the equations which define conditional probability, you can understand something about reality more than from your fantasy to math can reveal the simple underlying principles of reality. [00:06:28] Perhaps you know what simple. It is very hard to discover the. But then when you discover them and look at them, you see how beautiful they are. And and it is surprising why people did not. She said before you're working on an equation derived from equations, for example, I talked yesterday about a new school method and people have a lot of fun things. You have to improve it. But if you look going step by step by solving some equations, you're suddenly you get some term which after thinking you understand the described position of observation point where you throw out a lot of information. [00:07:23] You don't look in composition of point of observations. We look on residuals. But when you understood that, that's a very simple idea. But it's not too simple to understand. And you can derive this just from equations. [00:07:40] So some simple algebra is a few steps will take you to something surprising that when you think about. [00:07:49] And that is proof that human intuition not too rich and very primitive and it does not see very simple situations. So let me take a step back. And in general. Yes, right. [00:08:09] But what about human intuition? Ingenuity. [00:08:16] Moments of brilliance. So are you so do you have to be so hard on human intuition? Are there moments of brilliance and human intuition that can leap ahead of math and then the math will catch up? I don't think so. I think that is the best human creation it is putting in auctions and then it is technical work. See where the axioms take you. Yeah, but if they correctly take auctions but it your polish during generations or scientist and this is integral, use them so as beautifully put. [00:09:02] But if you maybe look at it when you, when you think of Einstein. And special relativity. What is the role of imagination coming first there in the moment of discovery of an idea? [00:09:19] To those, obviously, a mix of math and out of the box imagination there that I don't know, whatever I did or exclude any imagination. Because whatever I saw, emotional or the contrary, imagination like features, like deep learning, they're not relevant to the problem. When you're looking very carefully from what you might call equations, you deriving very simple theory which goes far beyond theoretical then whatever people can imagine because it is not good for. Yeah, it is just interpretation. [00:10:01] It is just fantasy. But it is not what you need. You don't need any imagination to derive the same principle of machine learning. [00:10:15] When you think about learning and intelligence, maybe thinking about the human brain and trying to describe mathematically the process of learning, that is something like what happens in the human brain. [00:10:28] Do you think we have the tools currently? Do you think we will ever have the tools to try to describe that process of learning you? It is not a description of what's going on. It is interpretation. It is your interpretation. Your vision can be wrong. You know, when God invent a microscope, living for the first time only got this instrument and nobody will. [00:10:56] He kept secrets about a microscope, but he wrote a report in London, the cardinal signs in his report when he looking at the blood, he looked everywhere on the water, on the blood, on the spill. [00:11:11] But he described blood like fight between Queen and King. So he saw blood cells, red cells, and he imagines that it is army fighting each other. [00:11:27] And it was his interpretation of situation. And he said that this report indicated no signs. They very carefully look because they believe that he's right. He's right. He saw something. Yes. But he gave wrong interpretation. And they believe the same can happen to his brain. Will be the most important, but, you know, I believe in human language, in some product is so much visible. For example, people say that it is better than a thousand days of diligent studies. [00:12:06] One day this great teacher. But if you ask your teacher does nobody knows. And that is intelligence. And but we know from history and know from from massive machine learning that teacher can do a lot to what from a mathematical point of view is a great teacher. [00:12:31] I don't know. That's not that. But we can see what teachers can do. You can introduce some environ, some predicate for creating convergence. How you doing it? I don't know, because teacher knows reality and can describe forms of reality, a predicate invariants. But he know that when you're using invariant, you can decrease the number of observations 100 times. [00:13:03] That's so. But maybe try to pull that apart a little bit. [00:13:08] I think you mentioned like a piano teacher saying to the student, play like a butterfly. [00:13:14] I played piano playing guitar for a long time. [00:13:18] Yeah, that's there's maybe a romantic poetic, but it feels like there's a lot of truth in that statement, like there is a lot of instruction in that statement. [00:13:30] And so you can't pull that apart. What what is that? [00:13:34] The language itself may not contain this information, not blah, blah, blah, because it's not other if you it's what affect you and affect your playing. Yes, it does. [00:13:45] But what it's not the length. It's it feels like what is the information being exchanged there? [00:13:53] What is the nature of information, what is the representation of that information? [00:13:56] I believe that it is sort of predicate, but I don't know. That's exactly what what intelligence and machine learning should be. Yes, because the rest is just mathematical technique. I think that what was discovered recently is that there is to try to mechanism of learning, one called strong convergence mechanism and the convergence mechanism before people use only one word in the convergence mechanism, you can use predicate. That's what's clearly butterfly. And if you immediately effect your playing, you know this that is English Brulard. [00:14:41] Great. If it looks like a duck, swims like a duck and quacks like a duck, then it is probably duck. Yes, but this is exact. Both predicates looks like a duck. What it means. So you so many ducks that your training data. So you, you have a description of how he looks into the looks ducks. [00:15:11] You have the visual characteristics of our duck. Yeah. Yeah. [00:15:14] But you want and you have model for your cognition so you would like. So that theoretical description from model coincide with empirical description each year. So tell them so about. Looks like the dogmatists general but what about. Seems like a dog. You should know that duck swims, you can say it looks like a duck duck doesn't play chess and it is completely legal predicate, but it is useless. So how did you can recognize not useless predicate? So up to now, we don't use this predicate in existing machinery and you think the zillions of data Watkins's English, but industry will probably use only three predicate. [00:16:10] Looks like a duck, seems like a duck and quacks like a duck. [00:16:14] So you can't deny the fact that swims like a duck and quacks like a duck, has humor in it, has ambiguity. Let's talk about swim like a duck. And it does not say jumps jumps like a duck. Why? [00:16:32] Because it's not relevant, but that's music, you know, ducks, you know, different birds, you know, animals. And you derive from this that it is relevant to say something like a jar. [00:16:47] So underneath, in order for us to understand swims like a duck, it feels like we need to know millions of other little pieces of information and we pick up along the way. [00:16:59] You don't think so? That doesn't need to be. [00:17:01] This knowledge base in in those statements carries some rich information that helps us understand the essence of duck. [00:17:10] Yeah. How far are we from integrating predicates? You know that when when you consider completely machine learning, so what it does, you have a lot of functions and then you're talking it looks like a duck. You see your training data from training data you recognize like. [00:17:41] Expecta. Doug should look, then you remove all functions, which does not look like you think it should look from training day, so you decrease in motor function from your pickup, what then? You give a second predicate and again, it decreases the set of function. And after that, you pick up the best function you can find it a standard machine learning. So why you need not too many examples. Your products aren't very good. Well, you're not such music. [00:18:23] Yeah, because every predicate is invented to decrease admissable set of function. So you talk about admissable set of functions and you talk about good functions. [00:18:37] So what makes a good function so admissable sort of function is sort of function which choose. [00:18:45] Small capacity of small diversity, small U.S. dimension, which contain good fortune and so, by the way, for people who don't know v.C, you're the V in the VC. [00:18:59] So how would you describe to a layperson what victory is? [00:19:05] How would you describe this rare mushroom smooshing? Capable to pick up one function from the admissable, set the function. But set of admissable function can be self-contained, all continuous functions and useless. You don't have so many examples to pick up function, but it can be small, small. We call it capacity, but maybe better diversity, so not very different function, settling in units at a function, but not very diverse. So it is small, we should mention when we mention a small unit, not the small amount of training that. [00:19:56] So the goal is to create admissable set of functions, which is have small we dimension and contain good function. Then you should you'll be able to pick up the function using small amount of observations. So that is the task of learning, yeah, is creating a set of admissible functions. [00:20:26] There's a small vesi dimension and then you figure out a clever way of picking up the vote that this goal of learning, which was not formulated yesterday, the statistical learning theory, does not involve in creating admissible set of function in classical learning theory everywhere, 100 percent. The textbook, the set of function admissable set of function is given. But this is sizable nothing because the most difficult problem to create admissable set of functions given see a lot of functions continue to function created missable set of functions. [00:21:10] That means that it is final three dimensions movie dimension and contain good function. So this was out of consideration. So what's the process of doing that? [00:21:22] I mean, it's fascinating. What is the process of creating this admissable set of functions that is invariant, that's in various. [00:21:30] Can you describe the variance, your string of properties of training data and, uh. Properties means that you serve some function in unit, you just can't what is your average value of function of training data? You have. Model and what is the expectation of dysfunction on the model and they should coincide so that the problem with both have to pick up functions, it can be a new function if in fact it is true for all functions. But because when we're talking set, say Doug does not jumping so you don't ask a question, jump like a duck because it is three really does the jumping doesn't help you to recognize. [00:22:31] But you know something which question to ask you asking. It seems like the job like a duck but looks like a duck at this general situation. Looks like a guy who have this illness is a disease that it is legal. Yeah. So there is a general type of predicate, looks like a special type of predicate which related to this specific problem. And that is intelligence part of all this business and that were teachers and incorporating the specialized predicates. [00:23:15] OK, what do you think about deep learning as as a neural networks, these arbitrary architectures, as helping accomplish some of the tasks you're thinking about, their effectiveness or lack thereof? What are what are the weaknesses and what are the possible strengths? [00:23:35] You know, I think that this is fun. You which like deep learning like teachers. Let me give you this example. [00:23:49] One of the greatest book, the Churchill book, about history of Second World War. And he's starting this book describing that in old time when war is over. So. The Great Kings. They gathered together, almost all of them were relatives, and they discussed what should be done, how to create peace. And they came to agreement on what will happen. First World War The. General public came in power and they were so greedy that Europe, Germany, and it was clear for everybody that it is not peace, that peace will last only 20 years because they was not professionals in the same way she in Washington Zarar mathematicians were looking for the problem. [00:24:50] From a very deep point of view, what you might call pointier and a computer scientists is mostly does not know mathematics. They just have interpretation of that. And they invented a lot of blah, blah, blah interpretations like deep learning. Why you get deployed does not know. Deploying mathematics does not know neurons. It is just function. If you like to say piecewise linear function, say that and do it in class of piecewise linear function. But they invent something and then they try to to to to prove advantage of that through interpretations which mostly wrong. [00:25:37] And then they, they appeal to brain which they know nothing about, that nobody knows what going on in the brain. [00:25:45] So I think the more reliable localness this is you much call problem to your quest to solve this problem, try to understand that there is more only one way of convergence, which is strong way of convergence. [00:26:01] There is a view of convergence which requires predicate. [00:26:04] And if you will go through all this stuff, you will see that you don't need diploid you even more. I would say one of the curium which called representativity. It says that the optimal solution. Of which medical problem, which is described learning is on schedule. Network not on deep loading and a shalonda or again, the problem is they're absolutely so in the end, what you're saying is exactly right. [00:26:44] The question is you have no value for throwing something on the table, playing with it, not math. [00:26:53] So can do all that work or you said throwing something in the bucket and or by the biological example and looking at kings and queens or the cells with a microscope, you don't see value in imagining the cells or kings and queens and using that as inspiration and imagination for where the math will eventually lead you. You think that interpretation basically deceives you in a way that's not productive? [00:27:21] I think that if you try to analyze this, the nature of learning and especially discussion about deep learning, it was a discussion about interpretation, not about since, about what you can say about things. That's right. But aren't you surprised by the beauty of it? [00:27:43] So not mathematical beauty, but the fact that it works at all? [00:27:50] Or are you criticizing that very beauty, our human desire to to interpret, to to find our silly, silly interpretations and these constructs like let me ask you this. [00:28:06] Are you. Surprised and does it inspire you? [00:28:12] How do you feel about the success of a system like Alpha Girl beating the game of go using neural networks to estimate the quality of a ball of a board and the quality of the. [00:28:26] Is your interpretation quality of support? Yeah, yes. Yeah. [00:28:32] But it's that interpretation. The fact is a neural network system doesn't matter. A learning system that we don't, I think mathematically understand that well, beats the best human player does something that was stolen in music. [00:28:47] It's not a very difficult problem that that's. [00:28:50] So you empiric we've empirically have discovered that this is not a very difficult problem. [00:28:55] Yeah, yeah, it's true. Uh, so maybe it's, uh, I can't argue. [00:29:02] Uh, so we were more I say the user use the Plotnick. It is not the most effective way of learning it. And usually when people use uploading, they're using zillions of training data. Yes, but you don't need this, so I describe a challenge, can we do some problems which you do? Well. Deep learning method is deep that are using a hundred times less training data, even more some problems, but deep learning cannot so. Because it's not necessary, they create admissable set of functionality to create the architecture means to create a reasonable set of functions, you cannot say that you create a good set of functions. [00:30:05] You're just that's your fantasy. It does not control much, but it is possible to create a reasonable set of functions because you have your training data. That actually, for mathematicians, when you're considered a lawyer, you need to use law of large numbers. When you're making training in existing algorithms, you need uniform law of large numbers, which is much more difficult to require. So we should mention another stop. [00:30:40] But nevertheless, if you use Morse and stroke way of convergence, you can decrease a lot of training that you could do. [00:30:50] The three the swims like a duck and quacks like a duck. But ah, so let's let's step back and. [00:31:00] Think about intel, human intelligence in general. And clearly, that has evolved in a non mathematical way. It wasn't as far as we know, God or whoever didn't come up with a model and place in our brain of admissable functions that kind of evolved. I don't know, maybe you have a view on this, but so Alan Turing in the 50s in his paper asked and rejected the question, can machines think? It's not a very useful question, but can you briefly entertain this useful, useless question? [00:31:38] Can machines think so? Talk about intelligence and your view of it? [00:31:43] I don't know that I know the critics describe imitation. If a computer can imitate human beings, let's call it intelligent. And he understands that it is not thinking computer. Yes, you completely understand what he's doing, but he set up problem of imitation. So now we understand that the problem not in imitation. I'm not sure that intelligence just inside of us, maybe also outside of us, I have several observations, so. When they prove something to him, it's very difficult. [00:32:28] So in a couple of years, in several places, people prove the same, showed him say so little after I was done. The other guys prove the same suit ever in the history of science. It's happened all the time. For example, geometry, it happened simultaneously. Did you have skills in girls and boys and other guys in it? Approximately 10 times period, the 10 year period of time? Mm hmm. [00:33:03] And I saw a lot of examples like that in which magicians that when they develop something, they develop something in general which affect everybody. So maybe our models of intelligence only inside of us is incorrect. [00:33:22] It's our interpretation that maybe they exist. Some connection with world intelligence, I don't know. [00:33:31] You're almost like plugging in into one. Yeah, exactly. And contributing to this network and into a big maybe neural network model. [00:33:43] And the flip side of that, maybe you can comment on big old complexity in how you see classifying algorithms by worst case running time in relation to their input. [00:33:57] So that way of thinking about functions. [00:34:00] Do you think P equals and P do you think that's an interesting question? It is interesting question, but let me talk about. Complexity in the boat, worst case scenario. The reason which a magical setting when they came to the United States in 1990, those people did not know the stories and did not know statistics. [00:34:27] So in Russia, it was published two monographs of monographs. But in America, they did not know that they learned. [00:34:37] And somebody told me that it is worst case scenario and they will create real chaos. [00:34:42] But still now it did not because it is much more logical to you can do only what you can do using your markings and which has a clear understanding and clear description. And for this reason, we introduce complexity and indeed this. Because. Using. Actually, it is divorcées like this one more this year dimension, you can prove some theorems, but they also create order for. Case of a new low probability measure, and that is the best case which can happen at the entropy suing. [00:35:32] So from what you might call point of view, you know, the best possible case and the worst possible case, you can draw a different model. [00:35:42] We don't, but if not so interesting, you think that the edges are interesting and they're just interesting because. It is not so easy to get good example. It's not many cases where the ball is not exact, but interesting principles. Did you discover the mass? [00:36:09] Do you think it's interesting because it's challenging and reveals interesting principles that allow you to get those bounds? Or do you think it's interesting because it's actually very useful for understanding the essence of a function of of an algorithm. [00:36:25] So it's like me judging your life as a human being by the worst thing you did in the best thing you did versus all the stuff in the middle. It seems not productive. [00:36:40] I don't think so, because you cannot describe a situation in the middle or if you're not general. So you can describe it just gorgeous. And it is clear because some model, but you cannot describe a model for every new case. [00:37:02] So you, you know, very accurate when you use, but from a statistical point of view, the way you've studied functions and and the nature of learning and the world, don't you think that the real world has a very long tail that the cases are very far away from? The mean the the stuff in the middle or no. I don't know that because I think that. But from my point of view. If you will use. Formal statistic, you uniformed law of large numbers. [00:37:55] If you will use. This. Invariance business, you don't you just love large numbers and there's a huge difference between uniformed law numbers and large numbers. [00:38:11] Is it useful to describe that a little more or shall we just take it now? For example, when we're talking about doc, I give three predicates if it was enough. But if you do try to to do formal distinguish, you will need a lot of observation. And so that means that information about looks like a duck. Contain a lot of bit of information, more bits of information, so we don't know that how much bits of information contain things from artificial intelligence and that is the subject of analysis know. [00:39:01] Old business. I don't like how people consider artificial intelligence. They consider us some quotes which imitate the activity of human beings. It is not science. It is applications you would like to imitate. Go ahead. It is very useful and a good problem, but. You need to to to to learn something more. Have people tried to do what people can to develop, say, predicates? [00:39:39] Seems like a duck or play like a butterfly or something like that, the lot not the teacher says you have it came in his mind how he chooses you. So that process has this problem of intelligence. That is the problem of intel. And you see that connected to the problem of learning. [00:40:00] Are they because you immediately give this predicate like specific predicate swims like a duck or quacks like a duck? [00:40:09] It was Wachusett somehow. So what is the line of work, would you say, if you were to formally as a set of open problems? [00:40:21] That will take us there to play like a butterfly will get a system to be able to let separate two stories, one, which a magical story that if you have predicate, you can do something in another story, you have to get predicate. It is intelligence problem. And people even did not start understand intelligence because to understand intelligence, first of all, try to understand what the teachers. Did you teach? I want one teacher better than another one. [00:40:59] Yeah, so you think we really even haven't started on the journey of not generating the president's you don't understand evil, don't understand this problem exist. Because did you do it? No, I just no name yet. I want to understand why one teacher but doesn't another. And have a teacher, student. It was not because he repeating the problem, which is textbook, he makes some remarks. He makes some philosophy of what he's saying, you know, that's beautiful. [00:41:39] So it is a formulation. Of a question that is the open problem, why is one teacher better than another, right? What she does, but. Yeah, what, what, what, why in every level, what people how do they get better, what does it mean to be better than the whole. [00:42:04] Yeah, yeah. From from whatever model I have. Yeah. One teacher can give a very good predicate. My teacher can say swims like a duck and another can say jump like a duck. And jump like a dog, courage, zero information. Yeah, so what is the most exciting problem in statistical learning you've ever worked on or are working on now? Oh, I just finished this invariance story. I very much hope is that I believe that it is ultimately. [00:42:43] Long story, at least they can show that there are no. If there's a mechanism or little mechanism, but they separate statistical but from intelligent plot and they know nothing about intelligent board. And if we do know the intelligent part. So if you'll help us. A lot in teaching and learning and learning. Yeah, you know, we'll know it when we see it. So, for example, in my talk, the last slide was a challenge. [00:43:21] So you have so NYST digital recognition problem and deplore the claim that they did it very well, say ninety nine point five percent of it. Correct answers, but say sixty thousand observations. Yeah. Can you do the same musical defenceless. But incorporating invariance, what it means, you know, they just want to say, yeah, just looking at that. Explain musician worry, and they should keep. To use the examples or say 100 times less examples to do the same job. [00:44:03] Yeah, that last slide in, unfortunately, you're talking ended quickly, but that last slide was a powerful, open challenge and a formulation of the essence of this exact problem of intelligence. [00:44:20] Because. Everybody, when when martial law started, it was developed much, much more efficient immediately recognise that we use much more training data as a human need. But now, again, we came to the same story after the case, that is a problem of learning. [00:44:45] It is not like in deep learning they use of subterranean bait. Because my vigilance is not enough, if you have a good invariance, maybe you'll never collect some more observations, but now it is a question to to intelligence. Have to do that because statistical part is ready as soon as you supply us this predicate, we can do a good job with a small amount of observations. And the very first challenge is low digit recognition and low digits. And please, there'll be variance, I think about that. [00:45:31] I can say four digits. Three, I would introduce concept of horizontal symmetry so that the digits really has horizontal symmetry, say more than, say, digits or something like that. [00:45:49] But as soon as I get to the horizontal cemetery, I can, which a watch could invent a lot of measure of horizontal symmetry or vertical symmetry or delusional symmetry or whatever, if I have a deal of symmetry. But what else? Look on digitizes it, it is the predicates. Which is not cheap to something like symmetry, like how dark this whole picture is, something like that. Each victim herself raised a predicate you think such a predicate could rise out of. [00:46:37] Something that's not general meaning. It feels like for me to be able to understand the difference between a two and three, I would need to have had a a childhood of 10 to 15 years playing with kids, going to school, being yelled by parents. All of that walking, jumping, looking at ducks, and now then I would be able to generate the right predicate for telling the difference in two or three, or do you think there's a more efficient way? [00:47:22] I know for sure that you must know something more than digits. [00:47:27] Yes. To that's a powerful state. [00:47:29] Yeah, but maybe there are several languages of description, the elements of digits. So I talking about symmetry, about symmetry, properties of geometry. I'm talking about something abstract. I don't know yet, but there's a problem of intelligence. So in one of our article, it is trivial to show that every example can cut a lot more than one bit of information in real, because, ah, when you show example and you say this is what you can remove, say, a function which does not tell you what say it's a best strategy if you can do it to remove half of the work. [00:48:25] But when you use one predicate, which looks like a duck, you can remove much more function and half. [00:48:33] And that means that it got a lot of formations. From formal point of view, but when you have. A general picture, what you want to recognize and general picture of the world. Can you just predicate. And that predicates got a lot of information. Beautifully put, maybe just me, but in all the material in your work, which is some of the most profound mathematical work in the field of learning, I just math in general. I hear a lot of poetry and philosophy. [00:49:19] You really kind of, um, talk about philosophy of science. There's a there's a poetry and music to a lot of the work you're doing and the way you're thinking about it. So do you. [00:49:30] Where does that come from? Do you escape to poetry? Do you escape to music or not resist ground truth. Resist ground truth. Yeah. And that can be seen everywhere. Yeah. The smart guy philosopher. Sometimes I surprise how the deep sea. [00:49:53] Sometimes I sees that some of them are completely out of subject. But. The grant also seen music. Music is the ground truth. Yeah, and in poetry, when people say they believe that. They take dictation, so what what piece of music? As a piece of empirical evidence gave you a sense that they are they're touching something in the ground truth, it is structure, the structure of the book. [00:50:34] Yeah, but you see this structure very clear, very classic. Very simple. It was the same was when you have axioms, enjoy the theory. You have the same feeling and at the same sometime you see the same. [00:50:50] Yeah. Um, and if you look back at your childhood, you grew up in Russia, you maybe were born as a researcher in Russia, you've developed as a researcher in Russia. You came to the United States in a few places. [00:51:06] If you look back, what were what was some of your happiest moments as a researcher? Some of the most profound moments, not in terms of their impact on society, but in terms of their impact and how damn good you feel that day. And you remember that moment. [00:51:30] You know, every time you follow something. [00:51:36] It is great things in life, every simple things, just the general feeling that they most most of my time was wrong, you should go again and again and again and try to be honest in front of yourself, not to make interpretation, but try to understand that it related to ground truth. It is not my blah, blah, blah interpretation and something like that. [00:52:07] But you're allowed to get excited at the at the possibility of discovery. Oh yeah. You have to double check it. [00:52:14] But no but covid related to the ground rules is it's just temporary. [00:52:22] Well it is for whatever you know, you always have a feeling when you found something have because that. [00:52:34] So 20 years ago, we discovered a statistical evidence, and so nobody believe except for one guy, doesn't it? Mm hmm. And then in 20 years, it became fashion was the same. The support vector machines, the kernel machines. [00:52:56] So with with support vector machines, the learning theory. But when you were working on it, you had a sense that you had a sense of the profundity of it, how that this this seems to be right. [00:53:14] This seems to be powerful, right? Absolutely. We immediately recognized that it will last forever. You know, when I found this. Invariance story. You feel the same way if I have a feeling that it is completely OK because I have proof that there are no different mechanisms, you can have some cosmetic improvement you can do. But in terms of invariance, you get more variance, statistical learning, extra work together. But also a secret is that, um, you can formulate what is intelligence of that. [00:54:06] And to separate from technical part. That is completely different, so, so well, Barbara, thank you so much for talking today. Thank you. It's an honor for the.

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