Talk:Finite-difference time-domain method

Problems with the popularity section

Where to start... First, it says that FDTD uses no linear algebra, which is nonsensical. Maybe whoever wrote that meant that FDTD avoids matrix inversions. Otherwise, the rest of the list is largely a rehashing of strengths of FDTD that were already listed in the rest of the article. Every single point in that list is a referenced to this one book. Is this section just a recreation of a section in the book? That doesn't seem to fit into the spirit of an encyclopedia. If there aren't any authors discussing FDTD's popularity apart from this one author, then this section isn't a good fit for a general encyclopedia, considering the same information is repeated elsewhere in the article already.142.244.63.13 (talk) 19:02, 18 January 2017 (UTC)

FDTD simulation software packages

Quite a few software simulation packages exist for the calculation of fields using the FDTD method. Two of these are widely used in research and development of active and passive microwave components: CST and the Vector Fields/CONCERTO package. Most researchers will use only one simulation software package, leading to the effect that the different packages aren't often comprehensively compared to one another.

Relevance of publication trend pic?

How useful is that pic in the final section? It seems like it takes up a lot of space for imparting very little information. I would think it sufficient to just state the general trend of publications on FDTD. 68.62.179.96 (talk) 05:51, 29 August 2008 (UTC)

I agree with that assessment. Do feel free to change the article. The button labelled edit at the top is there for a reason! -- Jitse Niesen (talk) 11:22, 29 August 2008 (UTC)

Alright, well I made this change and someone reverted it, saying that it was "essential to understanding the development of this technique." What is to be done here? I really see no reason why the growth of publications related to FDTD deserves more than a few sentences. Nor do I see any similar pics on pages for related techniques like Finite Element Method. I think I am going to delete the pic again and leave a note asking the next person who puts it back to post something on the this talk page. I hope this is not improper Wikipedia'ing!128.148.5.94 (talk) 06:23, 28 October 2008 (UTC)

I will respond. My perspective is one of a person who has been active in FDTD since 1971. Computational electromagnetics at the time involved ONLY phasor-domain techniques. Our early attempts to publish on what I called "FDTD" were all rejected by the major journals such as IEEE TAP. Our conference papers were relegated to the last day, last hour, when hardly anyone was left. There was incredible resistance to anything new coming from grid-based time-domain modeling. You were *not* there to face this resistance. I was, and I battled it one paper at a time -- doing the "homework problem" validations that disproved all of the doubters' claims of inaccuracy. I and a few others greatly expanded the scope of FDTD applications, and published the fundamental papers and books that eventually made FDTD perhaps the most widely used and powerful CEM technique. The near-exponential growth of FDTD publications shown by the graph in question is indicative of the turn of opinion by the worldwide CEM community. This graph vividly depicts when this occurred so that newcomers to the field realize just how recently all of this happened, and gain some perspective on the revolution in CEM brought about by FDTD. I argue strongly that we cannot and must not ignore this history. FDTD did not just come down from the sky. Its current widespread acceptance and use is the result of literally three decades of unceasing hard work against tall odds. Let this graph remain. Sincerely, Allen Taflove, Northwestern University —Preceding unsigned comment added by 24.12.211.91 (talk) 13:29, 29 October 2008 (UTC)

Dr. Taflove, no disrespect was meant and I am not trying to denigrate your contributions; however, I do not feel that the graph really conveys your above point. Perhaps it would be better served by a history section expanded from the brief paragraph in the introductory section of the article? The graph alone does not say much, and I think words would provide better context for the rise in the popularity of the technique.

128.148.155.57 (talk) 20:55, 29 October 2008 (UTC)

As an impartial observer, I'd have to agree with the OP - regardless of his familiarity with the method, his suggestion would seem to improve the article. Additionally I was about to make that same suggestion regarding a new history section, but he posted first. If that section were to grow bulky enough, then an offshoot-page ("History of the finite-difference time-domain method") should be created, and the graph would then be appropriate there. Beefnut (talk) 21:05, 29 October 2008 (UTC)

I have no objection to creating a history section, and would volunteer to draft one. It need not be bulky. Regards, Allen Taflove

Certainly, as you would seem to be uniquely positioned to do so.138.16.102.228 (talk) 20:36, 31 October 2008 (UTC)

As you can see, I have posted a draft history section for everyone to discuss. At this time, I've omitted the additional references that it cites, awaiting your comments. Thanks for the opportunity to provide some input to the FDTD page. Regards to all, Allen Taflove —Preceding unsigned comment added by 24.12.211.91 (talk) 20:33, 1 November 2008 (UTC)

The additional references are now posted. A few links to the source documents are missing, but will be added as available. Allen T. —Preceding unsigned comment added by 24.12.211.91 (talk) 21:41, 9 November 2008 (UTC)

The changes proposed by 193.147.222.244 have grammatical errors, add nothing to the article, and in fact, reduce the quality of the article. Hence, I've deleted them. Allen T. —Preceding unsigned comment added by 24.12.211.91 (talk) 14:58, 20 November 2008 (UTC)

There are many other possible reasons why publications have grown exponentially, such as the push in the mid ninties in academia to increase publication output. For example Why I am not a Professor. I would delete the whole section as mostly just fluff. If you wanted to make a statistical case it would be better to show that the proportion of papers in some well defined area (say papers published at IEEE_PDE) has increased markedly. --Jaded-view (talk) 23:56, 30 August 2009 (UTC)

Uses of FDTD

I think it is worthwhile to include subject areas where FDTD is used. I've started a list, I'm not qualified to cover all the areas. Thus I would appreciate if someone more qualified than me continues. I think it is very useful to know which subjects can benefit from FDTD.Eranus (talk) 14:28, 2 June 2009 (UTC)

It is pointless to attempt such a list — you'd be hard-pressed to find topics in electrodynamics that are not studied with FDTD except for magneto/electrostatic phenomena (where you only need the electric field or the magnetic field, but not both, since the coupling between the two is negligible in the quasistatic limit). You'd end up listing all topics in non-quasistatic electromagnetism.

(Sorry I reverted with the "rollback" button by mistake; I meant to press "undo" and add an edit summary). —Steven G. Johnson (talk) 17:45, 2 June 2009 (UTC)

I'm a Phd student investigating guided mode resonance and a realtively new user (and admiror) of MEEP which I understand you are an important contributor to. I do not have the wide scope, but at least for guided mode resonance I have confidence about where FDTD allows me to do things I could not do previously with RCWA for example, and where are it's difficulties. I thought it would be helpful for each expert to list in his subject area the advantages and disadvantages of FDTD. Do you think this may be a good idea as a separate page with a link from the main FDTD page? I think it is not a bad idea to have a long list of the vast topics in modern EM research and the advantages of FDTD in analyzing them? So the list will not be complete and only those who are Wiki users would update, but a partial list is better than non? Curious to hear your thoughts.Eranus (talk) 10:42, 3 June 2009 (UTC)

Listing the advantages of each method is an extremely tricky topic, because the advantages and disadvantages depend strongly on how the methods are implemented and on details of the problem. It is completely impossible to make blanket statements about the advantages of FDTD vs. RCWA for guided-mode resonances, for example: it depends on the nature of the guided mode and the waveguide geometries of interest, and it also depends strongly on how RCWA is implemented (RCWA is essentially yet another name for transfer/scattering-matrix methods based on eigenmode expansions, but there are many choices of basis for such things and many solution techniques) and how FDTD is implemented (e.g. some FDTD schemes have adaptive resolution, some (like Meep) are combined with special signal-processing techniques to extract resonances, and so on). Because of these facts, and also because it is hard to find papers making comprehensive comparisons of methods even for specific problems, it seems impractical to include such an article in Wikipedia.

Unfortunately, Wikipedia cannot simply rely on "experts in each area" to contribute their thoughts. Whether or not we can find experts in each area, that would be original research. We have to rely on already-published sources.

We have a brief overview and comparison of a number of different numerical approaches in appendix D of our book, which you can read online at http://ab-initio.mit.edu/book/ if you want. Perhaps this will be helpful to you. —Steven G. Johnson (talk) 12:31, 3 June 2009 (UTC)

Thank u for your detailed reply. BTW, I know the book well (even from it's previous version), unbelievable you guys post it online for free (Thats fantastic, very rare I think). What you say makes sense, though I think there are probably specific problems in modern optics that have been only simulated with FDTD and are published, I think it would be good to list these. I'll wait several more years to gain more perspective and experience as I'm very new in the world of numeric techniques (and Wikipedia). Eranus (talk) 13:35, 3 June 2009 (UTC)

FDTD is also used in acoustics, in particular architectural acoustics, to simulate the propagation of sound fields inside such as concert halls. How about mentioning this? 157.82.163.150 (talk) 05:56, 4 July 2010 (UTC)

This article should be renamed 'Electromagnetic applications of the FDTD Method'

The article seems to believe the method is only useful for electromagnetic problems, when in fact the FDTD framework is far more general in solving partial differential equations in time and space. Acoustics is another application (which also involves solving the wave equation), as well as problems involving the diffusion equation. Granted the majority of research (and publications) are in computational EM, but I don't believe the article's leading statement 'Finite-difference time-domain (FDTD) is a popular computational electrodynamics modeling technique' is in any way fair. —Preceding unsigned comment added by 35.9.42.83 (talk) 05:02, 15 October 2010 (UTC)

I think this is a fair point, but the suggested fix is wrong. If you have experience working with FDTD in other areas, expand this page to include them. But it is true hat by far the largest use of FDTD is electromagnetic. Yee, of Yee-cell fame, was working in electromagnetics. If you look further up this page, you will see comments from A. Taflove, another significant figure in the development of FDTD - as far as I know he has also worked mainly in electromagnetics. So, I expect this page will always have a strong EM bias, which I think fits well with majority use, but we should certainly make it clear that this is not the only use, and detail some other examples. GyroMagician (talk) 08:17, 15 October 2010 (UTC)

It is certainly true that the term "finite difference time domain" can be (and is) applied to many PDEs besides Maxwell's equations. It is also true the term "FDTD" appears to be most commonly applied to the electromagnetic application. However, I think it would be helpful to readers to make this distinction clear. Perhaps the article could be retitled to "Finite-difference time-domain method (electromagnetism)", following the usual Wikipedia disambiguation convention. — Steven G. Johnson (talk) 05:40, 16 October 2010 (UTC)

Agreed. I have added edits which demonstrate that the basic method is in fact much older (1928). It is equivalently and often used in scalar wave equation form, so why is this article so heavily focused on the electromagnetics applications? In fact, geophysics (Alterman 1968) and acoustics (Alford 1974) starting using the method in the late 60's early 70's as well. This article seems too biased towards Maxwell's equations and particularly, Allen Taflove's place in that field (too much material is straight out of his textbook). Many of the historical milestones in FDTD (in particular, ADI (much older than Zheng et al), and ABCs (Engquist & Majda (1979) (basis for Mur's ABC), Liao, Lindman (1975))) were not specific to CEM, but formulated by mathematicians. I think the title of this article should reflect the bias towards electromagnetics. — Preceding unsigned comment added by 82.39.75.98 (talk) 13:04, 11 February 2013 (UTC)

'FDTD' should redirect here

But I think that creating a new page with a redirect is above my permissions level as a non-registered user. 165.132.24.183 (talk) —Preceding undated comment added 10:43, 17 November 2011 (UTC).

FDTD already redirects here?! Is that what you intend? -- Crowsnest (talk) 13:36, 17 November 2011 (UTC)

Possible plagiate from book: Computational electrodynamics

The section Popularity contains seven reasons for the popularity of FDTD. This part seems to be copied verbatim from the book "Computational electrodynamics: the finite-difference time-domain method" by Allen Taflove and Susan C. Hagness. In the second edition the text can be found on page 4. It might be somewhere else in the recent third edition, but I don't have access to that.

The source should be indicated or the section removed / rephrased. — Preceding unsigned comment added by 128.131.210.49 (talk) 15:32, 6 February 2012 (UTC)

External links to vendors

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

---

I have removed the very long list of external links to vendors (for the second time). This is probably the worst violation of WP:ELNO#EL14 I have ever seen. It might be useful to somebody, but it has no place in an encyclopaedia. Specifically, it is a breach of the WP:NOTDIR policy. If there is discussion somewhere in reliable sources of the pros and cons of various packages then that can be in the article. But we cannot tolerate a spammy list that is completely open-ended with no clear criteria for inclusion. The link to the Open Directory Project was a reasonable compromise. If a vendor cannot get on that list there may well be a good reason. In any case, it is a list that is filtered by independent editors at ODP. SpinningSpark 20:28, 13 December 2012 (UTC)

Is a long list of software vendors acceptable in the external links section? Requesting input from other editors since the list has been restored. SpinningSpark 06:35, 14 December 2012 (UTC)

I agree that the list violates the WP:NOTDIR policy. But I am personally not bothered by a long list at the end; it doesn't really interrupt the flow of the article. It is a list of FDTD software packages; the best solution may be to put the list into its own page and refer to it in the See Also section. For example, the long List of finite element software packages is separate from the Finite element method page. A separate list page would allow the development of descriptions and comparisons of the packages, which could be invaluable to those who want to implement FDTD methods. Mark viking (talk) 13:42, 15 December 2012 (UTC)

How would you propose to reference such an article? References to the packages themselves do not really count as WP:RS. SpinningSpark 13:58, 15 December 2012 (UTC)

In the List of finite element software packages, most software packages reference their own Wikipedia articles; at present there is one with just an external reference. List of numerical analysis software is the same way, with more external references. Wikipedia articles are not necessarily reliable sources, but people seem OK with citing them in these lists. Vendors/projects can generally be relied upon to provide accurate technical specifications about their own software, it is just that they are not neutral. Perhaps they fall under WP:SELFSOURCE category of reliable sources? I haven't looked at the status of the FDTD packages to see if they have reliable secondary sources available or Wikipedia articles. Mark viking (talk) 14:35, 15 December 2012 (UTC)

What I object to here is the unqualified inclusion of all and sundry. If there were RS doing comparisons of packages that could be included (whether in the main article or a separate list article is irrelevant) but a list of EL without independent RS is not really acceptable. Comparisons with other articles does not really cut it either per WP:OTHERSTUFF. There is a place for article comparison to achieve consistency of style, but for establishing policy it is worthless: there must be millions of pages on Wikipedia that breach policy and guidelines in some way or another. SpinningSpark 17:04, 15 December 2012 (UTC)

Ah, I was simply suggesting a solution to an ungainly large software list that is the conventional solution to such problems at Wikipedia; there are many more lists of software pages and comparison of software pages than the two examples I gave. There are enough articles that are lists of software on Wikipedia that it is a convention and the warning against comparisons to arbitrary pages in WP:OTHERSTUFF doesn't really apply. Regarding external links not being cited by reliable independent sources, that is just about all of them at Wikipedia. As far as I can tell, the external links here fall under WP:ELMAYBE: the links may not be reliable sources themselves, but they still have useful information about FDTD modeling capabilities of their own software. Mark viking (talk) 18:21, 15 December 2012 (UTC)

I am not saying that EL should be reliably sourced, I am saying that EL should not be used as a substitute for a properly sourced list. SpinningSpark 23:04, 15 December 2012 (UTC)

Comment I am not inclined to suggest that I am much bothered. Both sides have merit, and my sympathies are mainly with MV, but I must say that if anyone raised formal objections to the list, it would be hard to sustain support for retaining it. Possibly pruning it to a list of "notable" packages or something?... Dunno. JonRichfield (talk) 21:03, 16 December 2012 (UTC)

Split I would start by splitting the list off to List of FDTD software. That seems to have worked well for List of numerical analysis software and List of PTP implementations, for instance. If that's not a fully acceptable solution you can then nominate the new article for deletion and debate it there. -—Kvng 15:18, 18 December 2012 (UTC)

• Split to List of finite-difference time-domain software as proposed above by Kvng, keeping only ones with sourcing. (I'm uninvolved, called by RFC bot) --Cyclopia^talk 10:54, 21 December 2012 (UTC)

For the record, RFC bot brought me here too. -—Kvng 13:23, 21 December 2012 (UTC)

Despite the verbiage, I am uninvolved with the FDTD article and came via RfC as well. Mark viking (talk) 14:09, 21 December 2012 (UTC)

• Comment. As EL, all the entries are already referenced to themselves, but currently, there are no independent sources discussing or comparing them. As it stands, I would be inclined to AfD such a list article were it to be created. SpinningSpark 21:39, 21 December 2012 (UTC)

We're not speaking of cut-and-paste the list as it is; it should be referenced to third party sources etc. --Cyclopia^talk 11:24, 24 December 2012 (UTC)

Do you have a source(s) that a list could be be based on? SpinningSpark 11:49, 24 December 2012 (UTC)

There are probably hundreds of lists on WP that are not collectively cited (there are three referred to in this discussion above). If you don't believe such lists should exist on WP, that's a larger issue that needs to be taken up elsewhere. -—Kvng 17:18, 24 December 2012 (UTC)

The list as it stands now does not belong. A list that consists of links to articles about the packages would be ok (but if too long should be its own article). Most of the linked software would not merit its own article at present, as not being notable enough. [the result is a list that isn't really useful to anyone except the target sites.] I recommend starting a page similar to List of numerical analysis software, and including one or two canonical examples as external links (say, to the largest open source projects, or to a third-party site that reviews and compares such software). – SJ + 21:47, 24 December 2012 (UTC)

Oh, and I <3 RFC-bot, which brought me also. – SJ +

Is it not very simple to understand in accordance to Wikipedia:External links as it states "Some external links are welcome (see What can normally be linked, below), but it is not Wikipedia's purpose to include a lengthy or comprehensive list of external links related to each topic." I have removed many long lists of external links from hundreds of articles. That means those must be reverted as what here is being discussed. I think Spinning is in right direction.Links should be removed except few.Thanks. Justice007 (talk) 17:05, 25 December 2012 (UTC)

I don't think anyone is supporting the external links section as it currently exists. The question is whether to just delete most of it or salvage it some way. -—Kvng 20:05, 25 December 2012 (UTC)

• Split - This method has worked in the past for similar articles. --Sue Rangell ✍ ✉ 21:12, 28 December 2012 (UTC)

• Trim the list mercilessly. Wikipedia is not web directory. Wikipedia lists are ususllay lists of wikipedia articles. Lists of software of unknown notability is not an option. Staszek Lem (talk) 17:44, 2 January 2013 (UTC)

• So... splitting didn't work, since there were too many redlinks. The list was deleted. Restoring just the major tools, in narrative form rather than as external links. – SJ + 00:38, 11 February 2013 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Deleted links to software / vendors

Since the conversation about external links to vendors which reached the conclusion that they should be deleted (see below), the links starting cropping up again. Deleted them again. — Preceding unsigned comment added by 80.176.222.197 (talk) 11:20, 27 January 2014 (UTC)

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Too much Frederick Moxley

Reading through this article, there is too much Frederick Moxley. There are three mentions of him in the section about important historical developments in fdtd(along with people like Yee and von Neumann), and the article ends with his "suggestion" to do other things with fdtd. Compared to someone like Taflove, who appears to be a major player, Moxley appears to have a minor academic record and not many citations for fdtd work. I suspect this is a case of self-promotion. — Preceding unsigned comment added by 128.149.87.38 (talk) 09:56, 28 September 2018 (UTC)

References