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Diffstat (limited to 'paper/sections/results.tex')
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1 files changed, 6 insertions, 39 deletions
diff --git a/paper/sections/results.tex b/paper/sections/results.tex index 7fca661..1db8288 100644 --- a/paper/sections/results.tex +++ b/paper/sections/results.tex @@ -47,28 +47,6 @@ log-likelihood function $\mathcal{L}$: it essentially captures the fact that the binary vectors of the set of active nodes (\emph{i.e} the measurement) are not \emph{too} collinear. -{\color{red} Rewrite the minimal assumptions necessary} -We will also need the following assumption on the inverse link function $f$ of -the generalized linear cascade model: -%\begin{equation} - %\tag{LF} - %\max\left(\left|\frac{f'}{f}(\inprod{\theta^*}{x})\right|, - %\left|\frac{f'}{1-f}(\inprod{\theta^*}{x})\right|\right)\leq - %\frac{1}{\alpha} -%\end{equation} -\begin{equation} - \tag{LF} - \max \left( \| (\log f)' \|_{\infty}, \|(\log (1-f))' \|_{\infty} \right) - \leq \frac{1}{\alpha} -\end{equation} -for some $\alpha\in(0, 1)$ and for all $x\in\reals^m$ such that -$f(\inprod{\theta^*}{x})\notin\{0,1\}$. - -In the voter model, $\frac{f'}{f}(z) = \frac{1}{z}$ and $\frac{f'}{f}(1-z) = -\frac{1}{1-z}$. Hence (LF) will hold as soon as $\alpha\leq \Theta_{i,j}\leq -1-\alpha$ for all $(i,j)\in E$ which is always satisfied for some $\alpha$ for -non-isolated nodes. In the Independent Cascade Model, $\frac{f'}{f}(z) = -\frac{1}{1-e^{-z}}$ and $\frac{f'}{1-f}(z) = -1$ and (LF) is not restrictive. \begin{comment} Remember that in this case we have $\Theta_{i,j} = \log(1-p_{i,j})$. These @@ -231,7 +209,7 @@ As before, edge recovery is a consequence of upper-bounding $\|\theta^* - \hat \frac{16}{\epsilon^2}\| \theta^* - \theta^*_{\lfloor s\rfloor}\|_1\right)s\log m \end{equation} -then similarly: ${\cal S}^*_{\eta + \epsilon} \subset \hat {\cal S}_\eta +then: ${\cal S}^*_{\eta + \epsilon} \subset \hat {\cal S}_\eta \subset {\cal S}^*$ w.p. at least $1-\frac{1}{m}$. \end{corollary} @@ -267,8 +245,8 @@ then \end{displaymath} and the $(S, \gamma)$-({\bf RE}) condition on the Hessian in Theorem~\ref{thm:main} and Theorem~\ref{thm:approx_sparse} reduces to a -condition on the \emph{gram matrix} of the observations $X^T X = -\frac{1}{|\mathcal{T}|}\sum_{t\in\mathcal{T}}x^t(x^t)^T$ with $\gamma \leftarrow +condition on the \emph{Gram matrix} of the observations $X^T X = +\frac{1}{|\mathcal{T}|}\sum_{t\in\mathcal{T}}x^t(x^t)^T$ for $\gamma' \defeq \gamma\cdot c$. \paragraph{(RE) with high probability} @@ -287,7 +265,7 @@ probability. If $f$ and $1-f$ are strictly log-convex, then the previous observations yields the following natural interpretation of the {\bf(RE)}-condition: the expected -\emph{gram matrix} $A \equiv \mathbb{E}[X^T X]$ is a matrix whose entry +\emph{Gram matrix} $A \equiv \mathbb{E}[X^T X]$ is a matrix whose entry $a_{i,j}$ is the average fraction of times node $i$ and node $j$ are infected at the same time during several runs of the cascade process. Note that the diagonal terms $a_{i,i}$ are simply the average fraction of times the @@ -295,24 +273,13 @@ corresponding node $i$ is infected. Therefore, under an assumption which only involves the probabilistic model and not the actual observations, Proposition~\ref{prop:fi} allows us to draw the -same conclusion as in Theorem~\ref{thm:main}. We will need the following -additional assumptions on the inverse link function $f$: -\begin{equation} - \tag{LF2} - \|f'\|_{\infty} \leq M - \text{ and } - \max\left(\left|\frac{f''}{1-f}\right|, - \left|\frac{f''}{f}\right|\right) - \leq\frac{1}{\alpha} -\end{equation} -whenever $f(\inprod{\theta^*}{x})\notin\{0,1\}$. These conditions are once -again non restrictive in the (IC) model and (V) model. +same conclusion as in Theorem~\ref{thm:main}. \begin{proposition} \label{prop:fi} Suppose $\E[\nabla^2\mathcal{L}(\theta^*)]$ verifies the $(S,\gamma)$-{\bf (RE)} condition and assume {\bf (LF)} and {\bf (LF2)}. For $\delta> 0$, if - $n^{1-\delta}\geq \frac{M+2}{21\gamma\alpha}s^2\log m $, then + $n^{1-\delta}\geq \frac{1}{28\gamma\alpha}s^2\log m $, then $\nabla^2\mathcal{L}(\theta^*)$ verifies the $(S,\frac{\gamma}{2})$-(RE) condition, w.p $\geq 1-e^{-n^\delta\log m}$. \end{proposition} |
