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=-1.0 required=5.0 tests=BAYES_00,FORGED_HOTMAIL_RCVD2, FREEMAIL_FROM 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 10.224.177.12 with SMTP id bg12mr1348852qab.0.1343313406818; Thu, 26 Jul 2012 07:36:46 -0700 (PDT) Received: by 10.66.86.232 with SMTP id s8mr1619143paz.47.1343313405267; Thu, 26 Jul 2012 07:36:45 -0700 (PDT) Path: a15ni105485768qag.0!nntp.google.com!q21no14547880qas.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!feeder7.xlned.com!multikabel.net!newsfeed10.multikabel.net!feed.xsnews.nl!border-3.ams.xsnews.nl!newsfeed.straub-nv.de!news.swapon.de!news.glorb.com!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail From: Austin Obyrne Newsgroups: comp.lang.ada Subject: Re: Computer operations per second - Question. Date: Sun, 22 Jul 2012 23:51:34 -0700 (PDT) Organization: http://groups.google.com Message-ID: References: NNTP-Posting-Host: 86.167.61.142 Mime-Version: 1.0 X-Trace: posting.google.com 1343026294 27864 127.0.0.1 (23 Jul 2012 06:51:34 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Mon, 23 Jul 2012 06:51:34 +0000 (UTC) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=86.167.61.142; posting-account=pmkN8QoAAAAtIhXRUfydb0SCISnwaeyg User-Agent: G2/1.0 X-Received-Bytes: 3995 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Date: 2012-07-22T23:51:34-07:00 List-Id: On Monday, July 23, 2012 7:10:10 AM UTC+1, Niklas Holsti wrote: > 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 =91n=92 operations per second. >=20 > If you are really *analysing* the time complexity (as a big-oh function= =20 > of problem size), based on the structure of the algorithm, the actual=20 > speed of your current computer is irrelevant. >=20 > If you want to compare or verify your analysis with measurements, the=20 > normal method is to measure the execution time as a function of problem= =20 > size and compare the shape of the measured function with the shape of=20 > the big-oh complexity function. In other words, to adjust the unknown=20 > constants in the big-oh function to fit the measurements. >=20 > > 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 =91n=92 =3D 2.61 x 10^6? >=20 > First, a giga is 10^9, not 10^6. Second, it all depends on what you mean= =20 > by an "operation". >=20 > > Can I assume that an operation is performed every cycle of the > > computer clock at 2.61 x10^6 operations persecond >=20 > Some basic "operations" are certainly performed at the stated= =20 > clock-rate, but what the operations are, in terms of your program,=20 > depends on many other factors, such as the nature and number of=20 > processor cores, the cache size, and the memory access patterns of your= =20 > program. The number of clock cycles needed to execute even a simple=20 > assignment statement such as X :=3D Y can vary from less than one to=20 > several thousand, depending on the presence or absence of X and Y in the= =20 > caches. >=20 > Current PCs are so complex that it is not useful to compare execution=20 > speeds of different algorithms when run on different PCs, unless the=20 > differences are very large (such as a factor of 5 or more). If you want= =20 > to compare the actual speed of your encryption method against other=20 > methods, you should run all the methods on the same PC (and on the same= =20 > data, of course). >=20 > --=20 > Niklas Holsti > Tidorum Ltd > niklas holsti tidorum fi > . @ . Thanks a lot Niklas - I suspected as much - it depends on may factors. - Au= stin O'Byrne.