Philippe Flajolet Does Research. Smokes. Battles Administration. Christian Konrad Reykjavik University December 12, 2014
Philippe Flajolet 1948 - 2011 Born: Dec. 1st, 1948 in Lyon Died: March 22nd, 2011 in Paris July 4th, 2006
Philippe Flajolet: Short Description 2004 “Does research. Smokes. Battles administration. Smokes. Wishes he could stop battling administration so that he could have more time to do research. Smokes some more. Gives jobs to starving foreigners. Eats occasionally.” — Eithne Murray
Luc Devroye on Philippe Flajolet Luc Devroye, My friend, Gaz. Math. No. 129 (2011), 116-117. July 4th, 2006
Luc Devroye on Philippe Flajolet Luc Devroye, My friend, Gaz. Math. No. 129 (2011), 116-117. The image that is etched in my mind is that of Philippe Flajolet happily purring while listening to a great exposition by one of his students or col- leagues. At the first opportunity, he would shout something funny in the direction of the speaker to show his appreciation. He was the community’s cheerleader. The inside of his car has never been cleaned, his hair cam- ouflaged a biological experiment, his shirts were always untucked, and yet, wherever he went, he was inevitably surrounded by friends and followers, admired for his brilliance and wit, and revered for his guidance and generos- ity.
Luc Devroye on Philippe Flajolet Luc Devroye, My friend, Gaz. Math. No. 129 (2011), 116-117. ... he was a master of mathematical illustration. He liked to show that craft off in his passionate talks, which grew more intense with every tick of the clock, to end up in overtime. On one occasion, I saw the last button of his shirt pop off just before the final slide. [He started wearing Indian-style shirts above his belt in the last decade of his life to avoid such events.] One of his other passions was listening. His seminar series in Versailles was legendary. It was an honour to be invited. And Philippe listened, purred, teased, shouted, applauded, and acted up - anything short of throwing a paper airplane at the speaker with a heart drawn on its wings. He was the glue that kept the community together.
Reactions About His Passing Away (1) Luc Devroye: wrote on March 22, 2011: I do not care about the world today. Philippe Flajolet died this afternoon. My heart is in the gutter. Why is it that the nicest, smartest, most generous guys have to go first? On Facebook: March 22, 2011—a day I will never forget. The world can go to hell. My friend, my brother, Philippe Flajolet just died. He was the guy I always wanted to be but never will be. Infinitely smart, generous, funny, radical, unconventional, creative, wonderful, wonderful, wonderful,.... Thank you Philippe.
Reactions About His Passing Away (2) Bob Sedgewick and Wojtek Spankowski The world has lost a brilliant and productive mathematician. Philippe’s untimely passing means that many things may never be known. But his legacy is a coterie of followers passionately devoted to Philippe and his mathematics who will carry on. Our conferences will include a toast to Philippe, our research will build upon his work, our papers will include the inscription ’Dedicated to the memory of Philippe Flajolet’, and we will teach generations to come. Dear friend, we miss you so very much, but rest assured that your spirit will live on in our work.
Reactions About His Passing Away (3) ALGO team webpage: Philippe Flajolet, our former Fearless Leader, died suddenly on March 22, 2011. Annus horribilis! Our band, which was so merry, is now extremely sad, and we remained voiceless for a lot of time. But, we cannot forget our beloved Pifou and his eternally renewed interest for algorithmics, mathematics, and Indo-European linguistics; his taste for good wine and good food; his constant humor.
Short CV 1958 - 1966 : Lyc´ ee Amp` ere in Lyon, Bac. 1968 - 1971 : ´ Ecole Polytechnique de Paris 1971 - 2011 : INRIA, Rocquencourt Recruited by Maurice Nivat 1976: Co-founder of the ALGO group (together with Jean Vuillemin) 1981: Head of the ALGO group 1972 : PhD, Universit´ e Paris Diderot Advisors: Maurice Nivat, Jean Vuillemin 1979 : Habilitation, Universit´ e Paris Sud
Short CV ´ Ecole Polytechnique
Short CV 1958 - 1966 : Lyc´ ee Amp` ere in Lyon, Bac. 1968 - 1971 : ´ Ecole Polytechnique de Paris 1971 - 2011 : INRIA, Rocquencourt Recruited by Maurice Nivat 1976: Co-founder of the ALGO group (together with Jean Vuillemin) 1981: Head of the ALGO group 1972 : PhD, Universit´ e Paris Diderot Advisors: Maurice Nivat, Jean Vuillemin 1979 : Habilitation, Universit´ e Paris Sud
Short CV INRIA Roquencourt
Short CV 1958 - 1966 : Lyc´ ee Amp` ere in Lyon, Bac. 1968 - 1971 : ´ Ecole Polytechnique de Paris 1971 - 2011 : INRIA, Rocquencourt Recruited by Maurice Nivat 1976: Co-founder of the ALGO group (together with Jean Vuillemin) 1981: Head of the ALGO group 1972 : PhD, Universit´ e Paris Diderot Advisors: Maurice Nivat, Jean Vuillemin 1979 : Habilitation, Universit´ e Paris Sud
Doctoral Advisors
Research “... a happy marriage between combinatorics and analysis applied to computer science and discrete mathematics.” Research Areas: Analytic Combinatorics (Average Case) Analysis of Algorithms Symbolic Computation Co-authored by Robert Sedgewick
Research “... a happy marriage between combinatorics and analysis applied to computer science and discrete mathematics.” Research Areas: Analytic Combinatorics (Average Case) Analysis of Algorithms Symbolic Computation Co-authored by Robert Sedgewick
Robert Sedgewick Robert Sedgewick : Data Movement in Odd-Even Merging . SIAM J. Comput. 7(3): 239-272 (1978) 2 � k π i � � 2 k π i � ln 2 · Γ ζ ln 2 ln 2 Philippe Flajolet et al.: On the Average Number of Registers Required for Evaluating Arithmetic Expressions . FOCS 1977: 196-205 2 k π i − log ... � k π i � � 2 k π i � Γ ζ log ... ln 2 ln 2
Robert Sedgewick Robert Sedgewick : Data Movement in Odd-Even Merging . SIAM J. Comput. 7(3): 239-272 (1978) 2 � k π i � � 2 k π i � ln 2 · Γ ζ ln 2 ln 2 Philippe Flajolet et al.: On the Average Number of Registers Required for Evaluating Arithmetic Expressions . FOCS 1977: 196-205 2 k π i − log ... � k π i � � 2 k π i � Γ ζ log ... ln 2 ln 2 I believe that we have a formula in common!
Analytic Combinatorics “Determine properties of combinatorial configurations through an approach based extensively on analytic methods.” Example: In how many ways can we lay n items on a table, in a row?
Analytic Combinatorics “Determine properties of combinatorial configurations through an approach based extensively on analytic methods.” Example: In how many ways can we lay n items on a table, in a row? Number of permutations of n elements n ! = 1 · 2 · 3 . . . ( n − 1) · n √ � n � n n ! 2 π n . (Stirling’s Formula) ≈ e Discovery of factorial function ∼ 500 B.C.
Analytic Combinatorics “Determine properties of combinatorial configurations through an approach based extensively on analytic methods.” Example: In how many ways can we lay n items on a table, in a row? Number of permutations of n elements n ! = 1 · 2 · 3 . . . ( n − 1) · n √ � n � n n ! 2 π n . (Stirling’s Formula) ≈ e Discovery of factorial function ∼ 500 B.C. How many alternating permutations are there for n = 1 , 3 , 5 , . . . ? 8 7 9 3 ր ց ր ց ր ց ր ց 4 6 5 1 2
Analytic Combinatorics “Determine properties of combinatorial configurations through an approach based extensively on analytic methods.” Example: In how many ways can we lay n items on a table, in a row? Number of permutations of n elements n ! = 1 · 2 · 3 . . . ( n − 1) · n √ � n � n n ! 2 π n . (Stirling’s Formula) ≈ e Discovery of factorial function ∼ 500 B.C. How many alternating permutations are there for n = 1 , 3 , 5 , . . . ? 8 7 9 3 ր ց ր ց ր ց ր ց 4 6 5 1 2 1 3 5 7 9 11 13 alt. perm. 1 2 16 272 7936 353792 22368256 n ! 1 6 120 5040 362880 39916800 6227020800
Analytic Combinatorics (2) 1 , 2 , 16 , 272 , 7936 , 353792 , 22368256 , . . . D´ esir´ e Andr´ e’s Discovery (1881): Taylor expansion of tan z 1! + 2 z 3 3! + 16 z 5 5! + 272 z 7 7! + 7936 z 9 9! + 353792 z 11 tan z = 1 z 11! + . . . tan z is a generating function of the sequence Symbolic Computation: Compute coeff. of Taylor expansion of tan z Can we get a closed formula for the coefficients?
Analytic Combinatorics (3) Analytic Methods: Approximate tan z at its singularities ± 1 2 π by “simple” function Deduce coefficients from simple function 1 3 5 7 9 11 13 15 Alt. Perm. 1 2 16 272 7936 353792 22368256 1903757312 Estimation 1 1 1 5 27 1 793 5 35379 1 2236825 1 1903757 267
Applications Algorithm analysis by analyzing underlying combinatorial structure Research Areas and Interests: Sorting algorithms Pattern in trees Factorization of integers and polynomials on finite fields Birthday paradox Queuing theory Probabilistic counting Number of distinct elements . . .
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