From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=0.4 required=5.0 tests=BAYES_00,FORGED_MUA_MOZILLA autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: a07f3367d7,bf2e2a640e02895 X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,CP1252 Received: by 10.66.77.199 with SMTP id u7mr1672020paw.25.1343319267107; Thu, 26 Jul 2012 09:14:27 -0700 (PDT) Received: by 10.68.227.67 with SMTP id ry3mr385106pbc.8.1343313197997; Thu, 26 Jul 2012 07:33:17 -0700 (PDT) Path: p10ni65138561pbh.1!nntp.google.com!u4no4636956pbs.0!news-out.google.com!p10ni61947386pbh.1!nntp.google.com!npeer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!news-in-01.newsfeed.easynews.com!easynews.com!easynews!novia!news-peer1!btnet!zen.net.uk!hamilton.zen.co.uk!xlned.com!feeder5.xlned.com!feed.xsnews.nl!border-3.ams.xsnews.nl!newsfeed.straub-nv.de!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Niklas Holsti Newsgroups: comp.lang.ada Subject: Re: Computer operations per second - Question. Date: Mon, 23 Jul 2012 09:10:10 +0300 Organization: Tidorum Ltd Message-ID: References: Mime-Version: 1.0 X-Trace: individual.net X88yqpOAUFZGsc7dcq7RVApmsiNqvyT0nZaEPZLc6HxlzamlL9Y8EQvVzhmCdo/qvg Cancel-Lock: sha1:GuLK28gLLKz7/YVt5q4ILppKkD8= User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 In-Reply-To: X-Received-Bytes: 3313 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Date: 2012-07-23T09:10:10+03:00 List-Id: On 12-07-22 23:20 , Austin Obyrne wrote: > I have just completed writing a very strong cryptographic cipher in > Ada-95 and I need to try and analyise the time complexity of this > cipher i.e the time taken to test a key space of 2560, > 000,000,000,000 keys at say �n� operations per second. If you are really *analysing* the time complexity (as a big-oh function of problem size), based on the structure of the algorithm, the actual speed of your current computer is irrelevant. If you want to compare or verify your analysis with measurements, the normal method is to measure the execution time as a function of problem size and compare the shape of the measured function with the shape of the big-oh complexity function. In other words, to adjust the unknown constants in the big-oh function to fit the measurements. > The processor of my home computer is a 2.61 GHz AMD processor and it > has 2.87 Gb of RAM. > > Is it correct for me say that my computer has a capability of 2.61 > Giga operations per second i.e �n� = 2.61 x 10^6? First, a giga is 10^9, not 10^6. Second, it all depends on what you mean by an "operation". > Can I assume that an operation is performed every cycle of the > computer clock at 2.61 x10^6 operations persecond Some basic "operations" are certainly performed at the stated clock-rate, but what the operations are, in terms of your program, depends on many other factors, such as the nature and number of processor cores, the cache size, and the memory access patterns of your program. The number of clock cycles needed to execute even a simple assignment statement such as X := Y can vary from less than one to several thousand, depending on the presence or absence of X and Y in the caches. Current PCs are so complex that it is not useful to compare execution speeds of different algorithms when run on different PCs, unless the differences are very large (such as a factor of 5 or more). If you want to compare the actual speed of your encryption method against other methods, you should run all the methods on the same PC (and on the same data, of course). -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ .