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| author | Thibaut Horel <thibaut.horel@gmail.com> | 2015-05-19 00:32:39 +0200 |
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| committer | Thibaut Horel <thibaut.horel@gmail.com> | 2015-05-19 00:32:39 +0200 |
| commit | 0fd1178dcffa025772bf5bfc43f24e692596747a (patch) | |
| tree | 30c634c871efe9116f291456be2f6b6587b37215 /paper/sections | |
| parent | 26bfc9b9e69facabe838fc35a96263e5c487c8b3 (diff) | |
| download | cascades-0fd1178dcffa025772bf5bfc43f24e692596747a.tar.gz | |
Final compression
Diffstat (limited to 'paper/sections')
| -rw-r--r-- | paper/sections/intro.tex | 5 | ||||
| -rw-r--r-- | paper/sections/model.tex | 1 | ||||
| -rw-r--r-- | paper/sections/results.tex | 12 |
3 files changed, 12 insertions, 6 deletions
diff --git a/paper/sections/intro.tex b/paper/sections/intro.tex index c89c641..cc29ed7 100644 --- a/paper/sections/intro.tex +++ b/paper/sections/intro.tex @@ -73,21 +73,26 @@ However, the best known upper bound to this day is $\O(s^2\log m)$~\cite{Netrapalli:2012, Daneshmand:2014} The contributions of this paper are the following: +\vspace{-1em} \begin{itemize} \item we formulate the Graph Inference problem in the context of discrete-time influence cascades as a sparse recovery problem for a specific type of Generalized Linear Model. This formulation notably encompasses the well-studied Independent Cascade Model and Voter Model. + \vspace{-0.5em} \item we give an algorithm which recovers the graph's edges using $\O(s\log m)$ cascades. Furthermore, we show that our algorithm is also able to efficiently recover the edge weights (the parameters of the influence model) up to an additive error term, + \vspace{-0.5em} \item we show that our algorithm is robust in cases where the signal to recover is approximately $s$-sparse by proving guarantees in the \emph{stable recovery} setting. + \vspace{-0.5em} \item we provide an almost tight lower bound of $\Omega(s\log \frac{m}{s})$ observations required for sparse recovery. \end{itemize} +\vspace{-0.5em} The organization of the paper is as follows: we conclude the introduction by a survey of the related work. In Section~\ref{sec:model} we present our model of diff --git a/paper/sections/model.tex b/paper/sections/model.tex index 5d3a232..ecf5ad6 100644 --- a/paper/sections/model.tex +++ b/paper/sections/model.tex @@ -234,6 +234,7 @@ cascades, the graph inference problem becomes a linear inverse problem. Bernoulli realization whose parameters are given by applying $f$ to the matrix-vector product, where the measurement matrix encodes which nodes are ``contagious'' at each time step.} +\vspace{-1em} \end{figure} Inferring the model parameter $\Theta$ from observed influence cascades is the diff --git a/paper/sections/results.tex b/paper/sections/results.tex index e91cad4..6b9fd7a 100644 --- a/paper/sections/results.tex +++ b/paper/sections/results.tex @@ -121,10 +121,10 @@ Assume {\bf(LF)} holds for some $\alpha>0$. For any $\delta\in(0,1)$: \end{lemma} The proof of Lemma~\ref{lem:ub} relies crucially on Azuma-Hoeffding's -inequality, which allows us to handle correlated observations. This departs from -the usual assumptions made in sparse recovery settings, where the sequence of -measurements are assumed to be independent from one another. We now show how -to use Theorem~\ref{thm:main} to recover the support of $\theta^*$, that is, to +inequality, which allows us to handle correlated observations. This departs +from the usual assumptions made in sparse recovery settings, that the +measurements are independent from one another. We now show how to +use Theorem~\ref{thm:main} to recover the support of $\theta^*$, that is, to solve the Network Inference problem. \begin{corollary} @@ -225,7 +225,7 @@ Observe that the Hessian of $\mathcal{L}$ can be seen as a re-weighted \bigg[x_i^{t+1}\frac{f''f-f'^2}{f^2}(\inprod{\theta^*}{x^t})\\ -(1-x_i^{t+1})\frac{f''(1-f) + f'^2}{(1-f)^2}(\inprod{\theta^*}{x^t})\bigg] \end{multline*} -If $f$ and $1-f$ are $c$-strictly log-convex~\cite{bagnoli2005log} for $c>0$, +If $f$ and $(1-f)$ are $c$-strictly log-convex for $c>0$, then $ \min\left((\log f)'', (\log (1-f))'' \right) \geq c $. This implies that the $(S, \gamma)$-({\bf RE}) condition in Theorem~\ref{thm:main} and Theorem~\ref{thm:approx_sparse} reduces to a condition on the \emph{Gram @@ -267,7 +267,7 @@ cascade, which are independent, we can apply Theorem 1.8 from \cite{rudelson:13}, lowering the number of required cascades to $s\log m \log^3( s\log m)$. -If $f$ and $1-f$ are strictly log-convex, then the previous observations show +If $f$ and $(1-f)$ are strictly log-convex, then the previous observations show that the quantity $\E[\nabla2\mathcal{L}(\theta^*)]$ in Proposition~\ref{prop:fi} can be replaced by the expected \emph{Gram matrix}: $A \equiv \mathbb{E}[X^T X]$. This matrix $A$ has a natural interpretation: the |
