Christophe,
I'm not making a general comparison between multiplication and exponentiation, I'm comparing exponentiation to the power 2 using the hat operator ^ with a valid --and simpler-- procedure to get the same result, i.e., multiplying the base times itself. I believe that functions and operators should parse the input arguments to exploit some special cases in which much more efficiency can be attained. The square is one such case, very important for its prevalence in many technical computations. My timings show that it is even more efficient to compute the general case c = a^b by c = exp(b*log(a)). So the algorithm being used for the general case is already more inefficient than it could be even by scripting, which is always more inefficient than a built-in. So it is not just a whim motivated by my use case but, rather, exposing a case which is susceptible of improvement. You say "It is a fact that amongst the several ways to compute one result, some are more efficient than others." OK, then, why not use the most efficient one? Another example: gamma() vs factorial(). Factorial is a special case of gamma function, yet it is slower. Try this: // Generate random integers --> tic, u = floor(20*rand(1, 1e6)); toc ans = 0.087116 // Compute factorial directly --> tic, v = factorial(u); toc ans = 0.7588414 // Compute factorial using gamma --> tic, v = gamma(u+1); toc ans = 0.2418619 Timing may vary across machines and operating systems, but the ratios are similar. Factorial is three times slower than using a special function. By the way, for integers up to 20, which yield numbers compatible with the precision of the arithmetic, the results are identical; above that the relative error is vanishingly small (about 1e-14) I have no idea which algorithm is being used for factorial (obviously, not multiplying all the factors), but its performance still leaves much to be desired. Regards, Federico Miyara
Except that the power is not a multiplication. It is a fact that amongst the several ways to compute one result, some are more efficient than others. Is the power function too slow regarding the algorithm it uses? Maybe, I don't know, but the comparison with the multiplication is not fair. https://help.scilab.org/power Regards -- Christophe Dang Ngoc Chan Mechanical calculation engineer Technology & Open Innovation Product Management & Development Sidel Group Sidel Blowing & Services Avenue de la Patrouille de France CS 60627, Octeville-sur-Mer 76059 Le Havre cedex, France Tel: 33(0)2 32 85 89 32 Fax: 33(0)2 32 85 91 17 <http://www.sidel.com/> <mailto:christophe.d...@sidel.com> This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error), please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. _______________________________________________ users mailing list - users@lists.scilab.org Click here to unsubscribe: <mailto:users-unsubscr...@lists.scilab.org> https://lists.scilab.org/mailman/listinfo/users This email and any attachments are intended solely for the use of the individual or entity to whom it is addressed and may be confidential and/or privileged. If you are not one of the named recipients or have received this email in error, (i) you should not read, disclose, or copy it, (ii) please notify sender of your receipt by reply email and delete this email and all attachments, (iii) Dassault Systèmes does not accept or assume any liability or responsibility for any use of or reliance on this email. Please be informed that your personal data are processed according to our data privacy policy as described on our website. Should you have any questions related to personal data protection, please contact 3DS Data Protection Officer https://www.3ds.com/privacy-policy/contact/
-- Este correo electrónico ha sido analizado en busca de virus por el software antivirus de Avast. www.avast.com _______________________________________________ users mailing list - users@lists.scilab.org Click here to unsubscribe: <mailto:users-unsubscr...@lists.scilab.org> https://lists.scilab.org/mailman/listinfo/users This email and any attachments are intended solely for the use of the individual or entity to whom it is addressed and may be confidential and/or privileged. If you are not one of the named recipients or have received this email in error, (i) you should not read, disclose, or copy it, (ii) please notify sender of your receipt by reply email and delete this email and all attachments, (iii) Dassault Systèmes does not accept or assume any liability or responsibility for any use of or reliance on this email. Please be informed that your personal data are processed according to our data privacy policy as described on our website. Should you have any questions related to personal data protection, please contact 3DS Data Protection Officer https://www.3ds.com/privacy-policy/contact/
