Re: GIFT does not find a query image relevant to itself when returning results.

Hi Nabeel,

this sounds indeed a bit weird, particularly that there are clear 
differences between the two versions!
In principle it can happen well that two images have no features in 
common and then the number of retrieved images will not be the size of 
the collection. This can particularly happen if you only use texture.

Which weighting do you use? Do you use the standard configuration file?

Cheers, Henning

Nabeel Mohammed (Infotech) wrote:
> Hello,
> I am trying to use GIFT for the research work associated with my PhD. I 
> had checked out the latest version from cvs to do my work and ran into a 
> problem.
> 
> I have an algorithm configured in my gift-config.mrml which uses just 
> the global texture features ( extracted using the bank of 12 Gabor 
> filters ). I was getting odd results from my test scripts. Looking into 
> the problem a bit more I realised that when I am querying with a single 
> query image, the first image returned (the most relevant) in the results 
> is not the image itself.  Infact the top relevant image seems to have a 
> relevance of less than 1. I have a total of 1670 images in my collection 
> ( a modified version of the VisTex database ), and this happens for 368 
> of them (I wrote a script to go through and do the sanity  check for 
> every single image). My supervisor ( Dr. David Squire) had .fts files 
> for the same collection, and using them also did not alter the behaviour 
> ( I regenerated the inverted files).
> 
> There is another issue where when for a query image I ask for 1670 
> results, for some images I don't always get back all 1670 (  about 1300 
> or so is returned). I can see how it may happen
> theoretically, but it seemed odd to me.
> 
> My environments are Ubuntu 9.10 running on Virtual Box on a windows 
> machine and a Mac. Both installations show the same issue.When 
> installing the pre-requisites I used the latest version of the Ubuntu 
> packages for my version of Ubuntu, instead of using the version numbers 
> mentioned in the readme file. Overall the compilation and installation 
> was relatively painless.
> 
> On the advice of David, I downloaded gift-0.1.14 and tried to compile it 
> on my environment. After a few changes I had it up and running. Using 
> the old collections still gave me the odd results.
> However, when I added a new collection using the same images using 
> gift-add-collection.pl <http://gift-add-collection.pl>, the insane 
> behaviour went away for the new collection. Also gift-0.1.14 behaves 
> sanely when I use the .fts files given to my by David and regenerate the 
> inverted files.
> 
> Also, for each image, gift-0.1.14 always returns all 1670 images, when I 
> ask for that result size.
> 
> 
> I've noticed that the code used to generate the Gabor features have 
> markedly changed in the cvs version since gift-0.1.14. I am not entirely 
> sure the two versions generate the same .fts files (I can check, but 
> haven't done so yet!). I think there is a problem in the inverted file 
> generation which causes gift to behave in such a way, but thats my 
> guess. I am wonderring if anyone knows of this problem,
> or has checked for it or knows how to solve it? If it is something I am 
> doing wrong, then I am hoping someone can tell me how to fix it.
> 
> Thank you
> Nabeel
> 
> 
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