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Learning to Re-rank: Query-Dependent Image Re-Ranking using Click Data Manik Varma Microsoft Research India Vidit Jain Yahoo! Labs India.

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Presentation on theme: "Learning to Re-rank: Query-Dependent Image Re-Ranking using Click Data Manik Varma Microsoft Research India Vidit Jain Yahoo! Labs India."— Presentation transcript:

1 Learning to Re-rank: Query-Dependent Image Re-Ranking using Click Data Manik Varma Microsoft Research India Vidit Jain Yahoo! Labs India

2 Keyword-based image search Best actress, Academy awards 2011 Natalie Portman Highest h-index in computer science Scott Shenker UC Berkeley

3 Scott Shenker similar results from other search engines

4 Our holy grail

5 Huge improvements in performance for tail queries Only the raw click data Efficient use of visual content In this talk

6 Limitation 1: Ignore visual content Simple visual processing could improve results

7 Score(x) = w t x with a fixed w Query : taj mahal Query : delhi Limitation 2: Static ranker within a vertical delhi.jpg tajmahal.jpg

8 Limitation 3: Noisy training labels Query : night train

9 Overview of our solution query Ranker Original ranked list Re-ranked list f* visual f* text Pseudo-click estimation clicked

10 Existing work for text document search linear scanning of ranked list relationship between relevance and clicks [Joachims07, Radlinski08, Agrawal09, Cutrell07, …] Our contribution for image search (challenge) 2D display of results (challenge) no model for browsing/click behavior use only raw click data Novelty in our use of click data

11 Evidence for clicks-relevance relationship (short snippet)(thumbnail) [Agichtein06]

12 Rich gets richer The curious case of distracting images Little gain when only a few were clicked Naïve solution – ClickBoosting Click-boosting ranked listOriginal ranked list

13 Pseudo-click estimation: Regression Query : night train (#clicks)

14 Visual features are not enough Need both visual and text features night rod Query : night train (#clicks)

15 Re-ranking function query Compute text features Compute visual features color, texture, shape query dependent query independent y text y visual Regression Score: s R (x) = a 1 s O (x) + a 2 y text (x) + a 3 y visual (x) sRsR sOsO

16 #features (~3000) >> #clicked images (~10) Dimensionality reduction unsupervised: only positive labeled data and the winner is… PCA !!! Bayesian formulation of regression Gaussian Process regression prevents over-fitting to small no. of examples non-optimized Matlab: 20 ms for a query with 20 clicked images Regression: challenges

17 Bing: top 1000 retrieved images for 19 tail queries e.g., gnats, Bern, fracture, child drinking water Relevance highly relevant, relevant, non-relevant referred to parent documents when needed used only for evaluation; not training Evaluation 20 (normalized discounted cumulative gain) Development set for experiments

18 Baseline: mean for Bing = SVR and 1-NN performance in between Pseudo-click estimation: Regression Approach Mean 20 Relative Improvement Linear Regression % GP Regression %

19 s R (x) = a 1 s O (x) + a 2 y Text (x) + a 3 y Visual (x) Re-scoring Function Approach Mean 20 Relative Improvement Baseline (a 2 = a 3 = 0)0.6854– Baseline + y Text (a 3 = 0) % Baseline + y Visual (a 2 = 0)0.6136–10.5% Baseline + y Text + y Visual %

20 Evaluation on 193 Queries

21

22 Query: fracture BingOur results Clicks predominately (~92%) on images of bone fracture

23 Query: gnats BingOur results Re-ranked list has only highly relevant images

24 Query: camel caravan BingOur results Anecdotally, our results were perceived as more visually pleasant

25 Query: turkey BingOur results Multiple interpretations are retained if manifested by clicks

26 Query: Stargate (1994) BingOur results Leads to visually diverse results for some queries

27 Significant improvement in over commercial image ranking system Use of raw click data Address three limitations of existing search engines incorporate visual features user clicks to handle noisy expert labels query-dependent re-ranking using GP regression Conclusions

28 Thank You!

29 Additional slides

30 Given a ranked list of relevance judgments R Cumulative Gain at P CG P (R) = i=1..P 2 R i – 1 Discounted Cumulative Gain DCG P (R) = i=1..P (2 R i – 1) / log 2 (i+1) Normalized Discounted Cumulative Gain nDCG P (R) = DCG P (R) / DCG P (I) where I is the judgment for the ideal ranked list Measuring Search Performance – nDCG

31 We only have positive training data so discriminative methods did not work well (generating negative training data is non-trivial) Simple methods did work well Click Estimation - Dimensionality Reduction Approach Mean nDCG at 20 Relative Improvement Average click rank0.6266– 8.6% Correlation with score % Correlation with clicks % PCA %

32 Gaussian Process Regression y(x) = k(x, x Train ) [ k(x Train, x Train ) + 2 I ] -1 y Train = d t (x, x Train ) y Train = w t (x) where y is the predicted number of clicks and y Train the number of clicks for the set of training images x are the features extracted from a novel image x Train are the training set features is a noise parameter k is a Gaussian kernel function Gaussian Process regression

33 Click Estimation - Regression Approach Mean nDCG at 20 Relative Improvement Linear Regression0.6871– 0.2% Support Vector Regression % Nearest Neighbour % GP Regression %


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