{"id":21316,"date":"2022-11-13T01:21:51","date_gmt":"2022-11-12T19:51:51","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-jensen-bregman-logdet-divergence-closed\/"},"modified":"2022-11-13T01:21:51","modified_gmt":"2022-11-12T19:51:51","slug":"solved-jensen-bregman-logdet-divergence-closed","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-jensen-bregman-logdet-divergence-closed\/","title":{"rendered":"[Solved] Jensen-Bregman LogDet divergence [closed]"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-30236092\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"30236092\" data-parentid=\"30223101\" data-score=\"1\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>As I understand it the function (of two symmetric positive definite matrices) is<\/p>\n<pre><code>JL(X,Y) = log( det( (X+Y)\/2)) - log( det( X*Y))\/2\n        = log( det( (X+Y)\/2)) - (log(det(X)) + log(det(Y)))\/2\n<\/code><\/pre>\n<p>I reckon the way to do this is to compute the cholesky factorisations of X, Y and (X+Y)\/2, that is find lower triangular matrices L,M,N so that<\/p>\n<pre><code>X = L*L'\nY = M*M'\n(X+Y)\/2 = N*N'\n<\/code><\/pre>\n<p>(I&#8217;m sorry to say I don&#8217;t know matlab, but there is bound to be a function to compute the cholesky factorisation).<\/p>\n<p>and then, using the properties of determinants and logs we have<\/p>\n<pre><code>JL(X,Y) = 2*log( det(N)) - log( det(L)) - log(det(M)))\n<\/code><\/pre>\n<p>For a lower triangular matrix K we have<\/p>\n<pre><code>log( det( K)) = log ( Prod( K[i,i], i=1..n))\n              = Sum ( log( K[i,i]), i=1..n))\n<\/code><\/pre>\n<p>I think it might be better to use the second form, even though it is slower, as there could be a risk of underflow in the product if the matrices are large, and perhaps the best thing to do would be to compute<\/p>\n<pre><code>JL(X,Y) = Sum ( 2*log( N[i,i]) - log( L[i,i]) - log( M[i,i]), i=1..n)\n        = Sum( log( N[i,i]*N[i,i] \/ (L[i,i]*M[i,i])), i=1..n)\n<\/code><\/pre>\n<p>Note that all of this assumes that the cholesky factorisations can be computed, i.e. that the matrices X and Y are strictly positive definite, but then the function JL is only defined in that case. <\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\"><\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved Jensen-Bregman LogDet divergence [closed] <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] As I understand it the function (of two symmetric positive definite matrices) is JL(X,Y) = log( det( (X+Y)\/2)) &#8211; log( det( X*Y))\/2 = log( det( (X+Y)\/2)) &#8211; (log(det(X)) + log(det(Y)))\/2 I reckon the way to do this is to compute the cholesky factorisations of X, Y and (X+Y)\/2, that is find lower triangular matrices &#8230; <a title=\"[Solved] Jensen-Bregman LogDet divergence [closed]\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-jensen-bregman-logdet-divergence-closed\/\" aria-label=\"More on [Solved] Jensen-Bregman LogDet divergence [closed]\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[457,357,516],"class_list":["post-21316","post","type-post","status-publish","format-standard","hentry","category-solved","tag-algorithm","tag-math","tag-matlab"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] Jensen-Bregman LogDet divergence [closed] - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-jensen-bregman-logdet-divergence-closed\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Jensen-Bregman LogDet divergence [closed] - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] As I understand it the function (of two symmetric positive definite matrices) is JL(X,Y) = log( det( (X+Y)\/2)) - log( det( X*Y))\/2 = log( det( (X+Y)\/2)) - (log(det(X)) + log(det(Y)))\/2 I reckon the way to do this is to compute the cholesky factorisations of X, Y and (X+Y)\/2, that is find lower triangular matrices ... 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