Such algorithms move through a search space by applying sequences of perturbations to a set of existing solutions. 2013) are typically employed to solve computationally hard optimisation problems. Search and optimisation methods such as metaheuristics (see Blum and Roli 2003) and hyper-heuristics (see Burke et al. The identification of subsequences of heuristic selections that can be shown to be effective across a number of problems or problem domains could have important implications for the design of future sequence based hyper-heuristics. Empirical results demonstrate that the “effective” subsequences perform significantly better than the “disruptive” subsequences across a number of problem domains with 99% confidence. These subsequences are then employed in a sequenced based hyper-heuristic and evaluated on an unseen set of benchmark problems. The sequences in the database are broken down into subsequences and the mathematical concept of a logarithmic return is used to discriminate between “effective” subsequences, which tend to decrease the objective value, and “disruptive” subsequences, which tend to increase the objective value. The resulting sequences of low level heuristic selections and objective function values are used to generate a database of heuristic selections. Google's browser caching recommendations.A selection hyper-heuristic is used to minimise the objective functions of a well-known set of benchmark problems.Webkit (Safari) computeFreshnessLifetimeForHTTPFamily().Internet Explorer (6+?), HTTPS caching in IE 8+, Internet Explorer 9+, Internet Explorer 9+.Firefox HTTP Caching FAQ, Firefox 38 ESR nsHttpResponseHead::ComputeFreshnessLifetime().2 HttpResponseHeaders::GetFreshnessLifetimes() IE 8 can have issues downloading files which it has been told not to cache.
HEURISTIC ALGORITHM USED BY RES2DINV FULL
Finding the details out is left as an exercise to the reader - and leaves the impression it is preferable to use different URLs for different content.Īllow the browser to make conditional requests by setting ETags.Įtags allow a browser to do a lightweight check to see if the content has changed and it can avoid making a full request if it hasn't.īe aware some browsers are just broken and need hacks. Chrome) use them and they have been superseded by Cache-Control. Yes, they have existed since the beginning but not all modern browsers (e.g. Expires: 0 and Pragma: no-cache are technically invalid response headers. In modern browsers Expires is superseded by Cache-Control. Finally, Chrome ignores cache directives in meta tags reducing their usefulness even further.ĭon't use the Expires header. Further, there can be problems when trying to use Pragma in IE. If you decide to go against this be aware that IE only recognizes two cache control directives that are set inside HTML: Īnd seemingly only the former is useful in the HTTPS scenario. Only use HTTP headers to control browser caching. In 2011 Firefox 4 (but not Safari) switched to opt-out caching for HTTPS content. Seemingly since its introduction Chrome has done opt-out for HTTPS (i.e.
Since at least 1996 IE has been using an opt-out policy for caching HTTPS content. There is only ONE standards based way of controlling caching (introduced with HTTP/1.1) - the Cache-Control HTTP header. IE5 has some terrible behaviour with caching headers). Let's assume all browsers we are interested in are Internet Explorer 8 or newer (e.g.
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