A first hires look at tetration \(\lambda = 1\) and \(b = e\)
#8
Hey!

I'll address Ember's concerns later tonight (my best guess is that you should initialize with a larger iteration depth, and add more terms to the series); and I'll do some tests with a larger period of \(\sqrt{2}\) for Sheldon.

I just wanted to quickly post some more graphs. This is for \(b = -\log(2)\)

   

And this is for \(b = 1/e\)

   




Quick update:


Code:
\r beta.gp

init(0.3,log(2)/2,500)            
%18 = 2.631096458622487533105232674332282321448030524841955893353502131514783001693269821395505376936048771562394003877698091183948664395503950719728846995192648240203544746340314048646010273735046291935196447187205197891833410441289897077722816061114574614833820726863519318709419123543937011250057653793313045829282898107397477075103258574939941723388723994967234082096494933055445889786376836670109965964856320731189118240930373227297559517898874450268827432478688622532519326328434535519902544400370535282435395821380154235083221984302198447692568782203961738103919630922937791824800330282245562973498018308523024032096425898239456533257333665783308056501418795810150614147985596084632112448875082019921952766370395725474256550516524405347456420908547124344401325959174335034457762909786158078516732668354654492118136268481379068299711375401508050365205973452994190052522777830795171627139536312574499186117911301251845620498210685451865585871630207402792466855481092330640963332394836791806714011826501 E-66*x^501 - 3.551608728253595611856992486866354231935644548617339428782544749165111641670135678286607591528745865709888943728866606599043785912191090317610385202615324419336808917224921715155621942329560763328537591602432786193428489669819776062644322181081577454680941375493838623380803472953962742842726699575513599825199063403079349021529656789967456653267328092950728075807360119559456377382360484239150491147929831731312248046142278554095557336706118502745368493508061026962242646395504763702494204895868428711474537318225158830603954868577666333308744139067712704148309370221539879773922630051684300138939163387395463361442263559726221004462619641965340490647278284714387726602256224293848926996915219592081672291108929419888740346443257848376798192882821094646609446930738765178576510745669827317290891863621108521232847370796686966725306324613525050941197156930964370126438136717756524147118195370600983652943572721469113764074807254719136666012343113103979899230082947560255071[+++]

beta(1) - exp(base*beta(0))/2
%19 = 0.E-1001

beta(3+I) - exp(base*beta(2+I))/(1+exp(-0.3*(2+I)))
%20 = 0.E-1001 + 0.E-1002*I

Sexp_N(8.57*I)
%21 = 3.999706578082077749667519088239874818457068382888025288693853120133488946393614418201645725102442014092576923221024443376471419942364668796395803908785526738240778062929719298841796957526587565049732889544485044534754733642315154942850182981625655457253805112552151892337520549269311557444341155015995863683684418262299183469233895833797714435999575746795028563095929476238122625874557355853526627606020414478257555557343548924115505421226082999959122482034968924799489255076503343643170779195951524522266609561477137406927033934100918933261558751726142422181650512047937874821400709667986890709225702893596512607881102983605616184694257652120929543100636557296195613735984226923083755862952597448535653336137777306556028092131688101363655212818717279089669730864191713814026860103590563768033399582848655870356519532662995230548571718980135191493838074013816426328947417521073317168584580071771535510106114715944141560246454318770428936985958956520554979520538165555864753664993377530126784943431371 + 0.00016399098349320826274344285773639576466432323053935938101282266586748104908489413418450033227869442673308967030910103025913297888850066784202994025079855245463790879230751569897404878723740662367631569911221429137554122186155482395023245562769064405072787483925649179232448064220188171154785763712415223342269534226015647014767276085435940775657164807001626711574503604030163557890775952363406618798393637734778549372380802838043961537819418247101883807970339880261032065838324326996790136059660463283001587548264474032123874713064683241508027661113872075732230499109682429232691890537542213111382036974048668744537688301371087124445852304764592519460889959088545279634686582440912180582548822946712276932141410533071373347085658813754967128005135289329032678412527975578994706152800185482083338182203427003286526440938309963162050281733939869501283429775674100188019955928635849513033693464077500816089572180569769608950078087973609269514599260766463417004549366061052822813064445[+++]



So yes, Sheldon, the fixed point 4 seems to be appearing for period \(2\pi i / 0.3\) at about \(8.57i\). Fascinating! The entire solution seems to be hovering about 4 too; I'll have to look into this. The best guess I have is that once \(\beta(z) > 2\) (by growing the period) taking successive \(\log\)'s just shoot us to the fixed point 4 very fast.


Ahh! I can get a better estimate. The value Sexp_N(z+36.5) is normalized to two digits and at here, if I write Sexp_N(8.57*I+36.5) we do not aggregate towards 4.  It appears way off in the left half plane we are in a neighborhood of 4; and as we push forward we get closer to 2. I'm making a graph as we speak; to see if any extraneous singularities appear.

It does not appear to produce anymore singularities than the ones at \(\pi i\). We seem to have a zipper effect, though. Where there's a whole lot of overflows very very close to the essential singularity (so its very possible we get a similar kind of singularity wall near these)--but they are no where near as prominent as with \(b=1\).  If I had to guess, there are probably branch cuts for \(|z - \pi i| < \delta\). The rule seems to be, as it explodes it gets too close to zero and creates a cluster of zeroes. For \(b=1\) it explodes almost everywhere; for \(b = \log(2)/2\) it seems much more rare; and only explodes near the singularities; and only really really close to the singularities.


As for your concerns Ember, I'm working on seeing if I use 1000 iterations that this solves the case for \(b \to -\infty\) and \(b \to \infty\) (I presume you are saying about 1 everything seems to be fine? I'm testing this either way. I think the key is just to run more iterations; as we should require far more iterations for these cases either way because \(\exp(b)\) is too small and doesn't contribute enough in each iteration, or \(exp(b)\) is too large and we flatline without gaining enough data; and \(b \to 0\) we definitely need more iterations because \(\exp(b)\) needs to multiply together a lot of times to be significant... I'll look closer though and see if I can get it to work.

And just to double check that you're calling everything correctly; recall that \(exp(bz)\) is my use of the value b in the program, not \(b^z\). I know that's confusing; but it does make for easier calculations; maybe I should call this the  log_base as opposed to the base...




Alright, so I see it working fine as I've written it if you do 1000 iterations, ember.

If you write:


Code:
init(1,log(1E13),1000)
%19 = 0.1298145027662377249554599157008877151682143003128644524757079278979362913866331797271701888068439189029209872646053124282157380258921547849503322680507451036011734448253090944559927527910545286015333130026970194332099683907825169797692000972496119598542982846706547311033815441682636620435312863262339908641392125140239246855244370238577057554318278553533344885496257772890926045914841936765733100350171996705751578801989804726133956504302479084323032007236624920688356199425463963007349873891702994687923301634644245859981765881732250210450892897055360680990897102889622121645463886586668151782613732020124539022262802611492957416960566976482150034972447346698347063745676475718520365761009248398644046500678573881216772113382666947611019405347879455445700750287079415002136218255589892403345359942280998188409417125477168811268463839261875676275872368827518089145095330990834954664787696406347928023695805125887443616425438846814665958822805420863277174567671590079176777470528316066082659636306803*x^1001 + 0.147473653053442865631157035427473875080867865829832534094307842262273160987865472789667798585872826705028909719280552151852480469856885972279146254360570603777109162529674839399414745828816933297154150029365357444694185877927574508812875030346865369823581099951894993399184536345315903822915508614797745973254831399717431826306771663307990820071325906154126433059687692945379394787638033500104486234170774527617199550685623554547057368964512626396057683789790726475291903574750343331728182074147135700498493931918915756219722892991984603849846691930385990580664095031201519801733037446841275199193311597043081561480021200639844254242094171930091932297620720336275574979761869970372424005743363470983026536013253019058536121928933420055121589855817764539236186515019925812179793469487936601288843002536394612391253572140129223915057964939964708246737777381152266543649543321701843605237792859647703079607066550372486881891851261130440387687071195091632534917545010042549125092[+++]

beta(0)
%20 = 1414450995945612060947115.320174756681858078057874605652777604893643857656899842844600963717877938156097005878927467624521771990046979564389001621458201307316280575942560885360833844103595073073467887931720315063957621577960489707592328361073821042747896857384772894295035129405458386859341578335548278492081505414799604926955500433383087653381943317601573349313619420005980289805175795845442890404224597322634803403014064158487550885342664377516178216641103991599046006266954512534337714831890884177315822337844298606004186426436051863650453955794783406851318828012079460937975363304619581521101908374132971855046068482249733595123149701247643351796165168357974007223011462677977535292905116259916897495207299586836827826381156556015893685614975389428591552177079245736865258045146262847552724116202126832916282670023587016096471516361895327419549062108248641702076730291867947132230197926184667100688309716636020900211538440589676900988142832395844445552122643741398290903668030316337825122762880688

beta(-1)
%21 = 1.901610016152517836127978333469384205313848906110750808508094436363114688118758605358383118047198930845250681200594120723639141038149107248709281697818058094157264168742309700134388265985357474781592768149778341026299059439784731120149254674959434807295352399322117521569249845868303777151841979920986302517212340090907787534681559432021598636376148785197130397225739780254441199518519742289277107591288431848424980010732274932098939724753124093484522901900359158447771190590225203656901236806994876625732865993018071615444654877883756429033856822812849918891732498892785952037697288153912660327603225963166736773060193081162071736491999611146989321643134859072697118463657038049726913351676697579063292119650620280956874815282245805922922401390587471049844997297665467747849653792639715692709789309451359813102461713401071296247253658303924317304914585609581499805528267876819983247380405155254744063134279789791048897579173416734162054688213666230778813995514168016909704910423171274534392751519390

beta(z) - exp(base*beta(z-1))/(1+exp(-mult*(z-1)))
%23 = 0.E-977 + 0.E-975*z + 0.E-972*z^2 + 0.E-970*z^3 + 0.E-968*z^4 + 0.E-966*z^5 + 0.E-965*z^6 + 0.E-963*z^7 + 0.E-961*z^8 + 0.E-959*z^9 + 0.E-958*z^10 + 0.E-956*z^11 + 0.E-955*z^12 + 0.E-953*z^13 + 0.E-952*z^14 + 0.E-950*z^15 + 0.E-949*z^16 + 0.E-948*z^17 + 0.E-946*z^18 + 0.E-945*z^19 + 0.E-944*z^20 + 0.E-942*z^21 + 0.E-941*z^22 + 0.E-940*z^23 + 0.E-938*z^24 + 0.E-937*z^25 + 0.E-936*z^26 + 0.E-934*z^27 + 0.E-933*z^28 + 0.E-932*z^29 + 0.E-931*z^30 + 0.E-929*z^31 + 0.E-928*z^32 + 0.E-927*z^33 + 0.E-926*z^34 + 0.E-925*z^35 + 0.E-923*z^36 + 0.E-922*z^37 + 0.E-921*z^38 + 0.E-920*z^39 + 0.E-919*z^40 + 0.E-918*z^41 + 0.E-916*z^42 + 0.E-915*z^43 + 0.E-914*z^44 + 0.E-913*z^45 + 0.E-912*z^46 + 0.E-911*z^47 + 0.E-910*z^48 + 0.E-909*z^49 + 0.E-907*z^50 + 0.E-906*z^51 + 0.E-905*z^52 + 0.E-904*z^53 + 0.E-903*z^54 + 0.E-902*z^55 + 0.E-901*z^56 + 0.E-900*z^57 + 0.E-899*z^58 + 0.E-898*z^59 + 0.E-897*z^60 + 0.E-896*z^61 + 0.E-894*z^62 + 0.E-894*z^63 + 0.E-892*z^64 + 0.E-891*z^65 + 0.E-891*z^66 + 0.E-889*z^67 + 0.E-888*z^68 + 0.E-887*z^69 + 0.E-886*z^70 + 0.E-885*z^71 + 0.E-884*z^72 + 0.E-883*z^73 + 0.E-882*z^74 + 0.E-881*z^75 + 0.E-880*z^76 + 0.E-879*z^77 + 0.E-878*z^78 + 0.E-877*z^79 + 0.E-876*z^80 + 0.E-875*z^81 + 0.E-874*z^82 + 0.E-873*z^83 + 0.E-872*z^84 + 0.E-871*z^85 + 0.E-870*z^86 + 0.E-869*z^87 + 0.E-869*z^88 + 0.E-867*z^89 + 0.E-866*z^90 + 0.E-866*z^91 + 0.E-865*z^92 + 0.E-864*z^93 + 0.E-863*z^94 + 0.E-862*z^95 + 0.E-861*z^96 + 0.E-860*z^97 + 0.E-859*z^98 + 0.E-858*z^99 + 0.E-857*z^100 + 0.E-856*z^101 + 0.E-855*z^102 + 0.E-854*z^103 + 0.E-853*z^104 + 0.E-852*z^105 + 0.E-851*z^106 + 0.E-851*z^107 + 0.E-850*z^108 + 0.E-849*z^109 + 0.E-848*z^110 + 0.E-847*z^111 + 0.E-846*z^112 + 0.E-845*z^113 + 0.E-844*z^114 + 0.E-843*z^115 + 0.E-842*z^116 + 0.E-841*z^117 + 0.E-840*z^118 + 0.E-839*z^119 + 0.E-838*z^120 + 0.E-838*z^121 + 0.E-837*z^122 + 0.E-836*z^123 + 0.E-835*z^124 + 0.E-834*z^125 + 0.E-833*z^126 + 0.E-832*z^127 + 0.E-831*z^128 + 0.E-830*z^129 + 0.E-830*z^130 + 0.E-829*z[+++]


The polynomial is accurate to about 1000 digits minus a 100 or so digits as you go further out in the Taylor series. So this works fine. Note, that for \(1E13^z\) we have to initialize \( b= \log(1E13)\).

Checking \(\exp(1E-5)\) everything seems to be fine too,

Code:
\r beta.gp
init(1,1E-5,1000)

%18 = 1.867330055199129483817007152110538060781215935289567548234021463168942214723070952518319438765136613995403148935429902384258796625604333525563289395831897344706412053257973078121074881788660653110056171469736600486189406493985861728687934327453061647205840843094381128273217297109896601886658152751270767897513317591536932820453332761119779087095385157289868666305206302376996104361749519689201347997796384813943245756218945129133013164573495328161655118001777903653222494402360106007627775757019651884142637666626524017922341017710344216523730233489789676656227987571164132924764426276951805170446725900830952225016751560028566276355701321607068298293997321006004129750152072144226069346654483291732435339995068922311145155201918512862496656560034151360645770804625885865552651243708886029803146201257801121545404880854114275019620107059968046945842422469617448684073297438526723880689324239609758630715608589289084176161224591052772118525851736242935331821866005175315608471224288553113244292534633 E-435*x^1001 - 5.0759293567832195619630136083908362475908694776195837301533141912936637457889786758986257116260422265063452260171480107148204940963719051340648424441435035678474814977882146675734690588594635177004047014910270176928768838597542076461604833887052188874336490947650419530024592679966528366142117704308090674550191865200147309588323391551062728866285304303543590278770416374807577796752986651982662441295486086053446184784321433604141123144761951206842909395418418039391966341626903834265909429323286332225048527564831163677048518326981444823215096164651843795503620764033806177240603813334343666068633793936666571711501844239447970306093006548282895751750809795318232072502434289358633230094085741399410799370763562817122164707528223796034289907910768546277410484589018556115620693341512349928888062772793109530446328256037828689134132576576692095763686217833484052211485062751436848109509509644671469840883707760349093315928095502131386138569227559129375366790113028450630[+++]

beta(z+1) - exp(base*beta(z))/(1+exp(-mult*z))
%19 = 0.E-1021 + 0.E-1021*z + 0.E-1007*z^2 + 0.E-1022*z^3 + 0.E-1008*z^4 + 0.E-1023*z^5 + 0.E-1009*z^6 + 0.E-1024*z^7 + 0.E-1011*z^8 + 0.E-1025*z^9 + 0.E-1012*z^10 + 0.E-1026*z^11 + 0.E-1012*z^12 + 0.E-1027*z^13 + 0.E-1013*z^14 + 0.E-1028*z^15 + 0.E-1015*z^16 + 0.E-1029*z^17 + 0.E-1016*z^18 + 0.E-1030*z^19 + 0.E-1017*z^20 + 0.E-1031*z^21 + 0.E-1018*z^22 + 0.E-1032*z^23 + 0.E-1018*z^24 + 0.E-1033*z^25 + 0.E-1020*z^26 + 0.E-1034*z^27 + 0.E-1021*z^28 + 0.E-1035*z^29 + 0.E-1023*z^30 + 0.E-1036*z^31 + 0.E-1023*z^32 + 0.E-1037*z^33 + 0.E-1024*z^34 + 0.E-1038*z^35 + 0.E-1025*z^36 + 0.E-1039*z^37 + 0.E-1026*z^38 + 0.E-1040*z^39 + 0.E-1028*z^40 + 0.E-1041*z^41 + 0.E-1028*z^42 + 0.E-1042*z^43 + 0.E-1029*z^44 + 0.E-1043*z^45 + 0.E-1030*z^46 + 0.E-1044*z^47 + 0.E-1031*z^48 + 0.E-1045*z^49 + 0.E-1034*z^50 + 0.E-1046*z^51 + 0.E-1033*z^52 + 0.E-1047*z^53 + 0.E-1034*z^54 + 0.E-1048*z^55 + 0.E-1035*z^56 + 0.E-1049*z^57 + 0.E-1037*z^58 + 0.E-1050*z^59 + 0.E-1039*z^60 + 0.E-1051*z^61 + 0.E-1039*z^62 + 0.E-1052*z^63 + 0.E-1039*z^64 + 0.E-1053*z^65 + 0.E-1040*z^66 + 0.E-1054*z^67 + 0.E-1042*z^68 + 0.E-1055*z^69 + 0.E-1043*z^70 + 0.E-1056*z^71 + 0.E-1044*z^72 + 0.E-1057*z^73 + 0.E-1045*z^74 + 0.E-1058*z^75 + 0.E-1046*z^76 + 0.E-1059*z^77 + 0.E-1047*z^78 + 0.E-1060*z^79 + 0.E-1048*z^80 + 0.E-1061*z^81 + 0.E-1049*z^82 + 0.E-1062*z^83 + 0.E-1050*z^84 + 0.E-1063*z^85 + 0.E-1051*z^86 + 0.E-1064*z^87 + 0.E-1052*z^88 + 0.E-1065*z^89 + 0.E-1053*z^90 + 0.E-1066*z^91 + 0.E-1054*z^92 + 0.E-1067*z^93 + 0.E-1055*z^94 + 0.E-1068*z^95 + 0.E-1056*z^96 + 0.E-1069*z^97 + 0.E-1057*z^98 + 0.E-1070*z^99 + 0.E-1059*z^100 + 0.E-1071*z^101 + 0.E-1059*z^102 + 0.E-1072*z^103 + 0.E-1060*z^104 + 0.E-1073*z^105 + 0.E-1061*z^106 + 0.E-1074*z^107 + 0.E-1062*z^108 + 0.E-1075*z^109 + 0.E-1064*z^110 + 0.E-1076*z^111 + 0.E-1065*z^112 + 0.E-1077*z^113 + 0.E-1065*z^114 + 0.E-1078*z^115 + 0.E-1066*z^116 + 0.E-1079*z^117 + 0.E-1067*z^118 + 0.E-1080*z^119 + 0.E-1069*z^120 + 0.E-1081*z^121 + 0.E-1070*z^122 + 0.E-1082*z^123[+++]

beta(0)
%20 = 0.2689417419563710366039719472062873185215020928828650674321273582658311568854302231048803149537725115669719644592365691206024833703045301897804905756961127940104712047578049180583976391795876503241764058281940782410310734537112064321154976730554798700952031985773854188740355169461834265977900484617254533553336430584117575930526696609993354791202354778229856674615022593482430368177769171363496160987180732750808086063903949784337778283041175541285255317781996894878796384571813251925774234953035560127138989095781243264371493256906396384217070715231641943620520770500995971026312972865815795790139999797010542197134103981965377264006463739392027985985185642276544688206021511426727865321224504696377093331210970273315994516193548262696720420057000427947393581818941111820791134295482029254004345757705541869723534080784223288326684428309580168593254754227394719873458643186109020492843037719079618914694627511607000439817514803588350166554987436033554204857212529991108599169640595492976506859763207

And also for \(\exp(1E-5)\) this seems to be working fine, where I've done 1000 iterations again.

Looking at \(\exp(-1E5)\) everything seems fine too, 1000 iterations seems to be the key.

Code:
\r beta.gp
init(1,-1E5,1000)
       
%18 = 9.466881219443518654605370147335949951251837259112187304427745580057432085900873327044139987840663420717783316386290363754656360091342015745092657075911673953262784855213003432585717767942192848902012409484641595920316001151496059574348580665643124765947898493918040650796054455164878618494141749427861236237647398475914155233265601769580250450752576189625338512346513114902606577393235755215036652953055732628116966118989902211831105973626759837602361829038061000228316257010769274960918786321323103138035798512099608429710738181456487098350868520520356438400959339348666900964072585498257771579322568240201530189609307769620004289329749721385782802956381701750213197734241524077054275514604162865490052381917671158035390458000415800630560344705521593734128583470360203765691622573521637742380997943971167584571327292934521761349537602186646384781324780674339800153469113186324721678548032659213522717766812469724848364899424773262678589242417640441864999075477682356078027647351416626681357007313160 E3544*x^1001 - 3.0599953829150688142081242293249888303681584520093663493304439032593179049702875520285452858127147769623184230606469865656375242352479521819403986461698183551076746501539188781221340157735139692402945464989369117607242279733242347391047439188365626082255580048878029177404303035563562380100627597857145478096762915287687601054126071440356506237922183349324127889517739983338966225707203360854361847206752806538514031046514069107827715556229651500460132657334538161709421262347279975925950349908506010871615652871738112399403748268151394423455468182929984351904268668098998041319497812725269922650660393909620981552212901211014036588208344003260113617140154571700876807787903101084575233281192606904915472959432894461210242502091654708909054825573158865441834166136945890528378377472525297584952932241862057413663015312321487787178325466119722395772576688807421855484290847685951771036960626255281005860136883947858659135520087164847526896019219977701047392229656829285362[+++]

beta(0)
%19 = 0.2689414213699951207488407581781637256348553598349434807236340920809595469297953606125254679240187547078255335068592254335588672690652010520214276941920607183354336479166115304013137160346148649813492756957003687952091081940535504266480986153893321591085761333389050293676059934603293561309628998999520352121612007828243337426386436001987833121463197736652484862552352223417798474659899584614026622157472965450918158838274968608551169827677953740491169754122846568846384258169856132825812401694860612081747698667812435006064342201362165251624951611544121351796968796669662868138541682614605142088833395610168874213350871482822493046910113973156096096554920649461710601929290740963614676083778709036887742869953146280360183027838514179142972103901064656367799729101972135969323384280212697664890134818576566327320339551224766083137358268157135685206321004591730269800124610781727476896167628347329246233920429626004145502166780491946937912046971914841015662929646423256253710776395126958520336218064325

beta(1)
%20 = 5.265557792007748655013092371115806082275788083416767092496807686592646318537349838483082957100807697218634715319914617704079125086410923234779061912897693893915319405948476744902352809614410679494663556344851261085928796868356161949249788828717970604243208924621885557001698203363492134961277837011039856345709922644830790268853421336362576162637971908867335599081278989117876710855805837490367919748669368851066150925882766842582649502470781362709861327653560440689558366042310067084121811240184550799349338313216643491636985749804150282634637249487948908137242809141972073901749714815054656102612403666513896432868358039293215264007471728269804057238755943449106129986465966520551220746527764744415797766770918594388459299772014589292694325536755469770364737152952317211470609361970934307614032515242052181700066886368133325937543598698081176307158189735878908122321654065616007171452444077885812332265243448236602221279147025327081648155219743599331955969230771630055466922331114770725228656394136 E-11681

beta(z+1) - exp(base*beta(z))/(1+exp(-mult*z))
%21 = 0.E-12682 + 0.E-12677*z + 0.E-12673*z^2 + 0.E-12669*z^3 + 0.E-12666*z^4 + 0.E-12662*z^5 + 0.E-12658*z^6 + 0.E-12655*z^7 + 0.E-12652*z^8 + 0.E-12648*z^9 + 0.E-12645*z^10 + 0.E-12642*z^11 + 0.E-12639*z^12 + 0.E-12636*z^13 + 0.E-12632*z^14 + 0.E-12629*z^15 + 0.E-12626*z^16 + 0.E-12623*z^17 + 0.E-12620*z^18 + 0.E-12617*z^19 + 0.E-12614*z^20 + 0.E-12611*z^21 + 0.E-12608*z^22 + 0.E-12605*z^23 + 0.E-12602*z^24 + 0.E-12599*z^25 + 0.E-12596*z^26 + 0.E-12594*z^27 + 0.E-12591*z^28 + 0.E-12588*z^29 + 0.E-12585*z^30 + 0.E-12582*z^31 + 0.E-12580*z^32 + 0.E-12577*z^33 + 0.E-12574*z^34 + 0.E-12571*z^35 + 0.E-12568*z^36 + 0.E-12566*z^37 + 0.E-12563*z^38 + 0.E-12560*z^39 + 0.E-12558*z^40 + 0.E-12555*z^41 + 0.E-12552*z^42 + 0.E-12550*z^43 + 0.E-12547*z^44 + 0.E-12544*z^45 + 0.E-12542*z^46 + 0.E-12539*z^47 + 0.E-12536*z^48 + 0.E-12534*z^49 + 0.E-12531*z^50 + 0.E-12529*z^51 + 0.E-12526*z^52 + 0.E-12524*z^53 + 0.E-12521*z^54 + 0.E-12518*z^55 + 0.E-12516*z^56 + 0.E-12513*z^57 + 0.E-12511*z^58 + 0.E-12508*z^59 + 0.E-12506*z^60 + 0.E-12503*z^61 + 0.E-12501*z^62 + 0.E-12498*z^63 + 0.E-12496*z^64 + 0.E-12493*z^65 + 0.E-12491*z^66 + 0.E-12488*z^67 + 0.E-12486*z^68 + 0.E-12484*z^69 + 0.E-12481*z^70 + 0.E-12479*z^71 + 0.E-12476*z^72 + 0.E-12474*z^73 + 0.E-12471*z^74 + 0.E-12469*z^75 + 0.E-12466*z^76 + 0.E-12464*z^77 + 0.E-12462*z^78 + 0.E-12459*z^79 + 0.E-12457*z^80 + 0.E-12455*z^81 + 0.E-12452*z^82 + 0.E-12450*z^83 + 0.E-12447*z^84 + 0.E-12445*z^85 + 0.E-12443*z^86 + 0.E-12440*z^87 + 0.E-12438*z^88 + 0.E-12436*z^89 + 0.E-12433*z^90 + 0.E-12431*z^91 + 0.E-12429*z^92 + 0.E-12426*z^93 + 0.E-12424*z^94 + 0.E-12422*z^95 + 0.E-12419*z^96 + 0.E-12417*z^97 + 0.E-12415*z^98 + 0.E-12412*z^99 + 0.E-12410*z^100 + 0.E-12408*z^101 + 0.E-12406*z^102 + 0.E-12403*z^103 + 0.E-12401*z^104 + 0.E-12399*z^105 + 0.E-12397*z^106 + 0.E-12394*z^107 + 0.E-12392*z^108 + 0.E-12390*z^109 + 0.E-12387*z^110 + 0.E-12385*z^111 + 0.E-12383*z^112 + 0.E-12381*z^113 + 0.E-12378*z^114 + 0.E-12376*z^115 + 0.E-12374*z^116 +[+++]


It actually works exceptionally well here! We get 12000 digit accuracy--though that's probably because it's in the neighborhood of zero already!!

For fun, I tried a negative value too; so here's \(\exp(1E-5+\pi i) \approx -1\):

Code:
\r beta.gp
init(1,1E-5+Pi*I)
%18 = (6.370542742196280583271196011243055529609616969230416418975693471398271256043809855993588966505844008389430073737333624266272315633971391655020238482289133595693603849790128084325849637962018872778105017781045480944105604404928676704220427083454387083174477194028999771721571824304859910948562893234920920144238260266350548946099572300884919501437655419713569084209637174288915301918557676343391028562876220465491003641203916859245637484901596954001267485931828154549822425601127129480258643144133494835531165837467795638548699283010420808905842684274737267878448077630692084009235093601932309417771074465417168611782862529727540585132533424491509111741165342825341702392648620450351697075130677239674525456173761513139933256484527047373904372381671987450941491160974330261434292971439612825007000742556997028841204139096302316396801379176073556530669543809836490102472143883833429375843678290681961061786627858276086720738123020158264971460586756379130763600803819506362335324386508437435173940198640 E-133 - 8.6549194480179078100250356345375662348390403555734463835315064376278081499758091500079127306832798907291609062661381712675245507350531109736502841315863489658788498409250059265884559523014613982402318213204231080001663718229688196798536016094468032225248382907146440490053534536410115061902555327014878060445767814975103641891965247332011805290470169038006302564869743161505133388888531891975103328661652195878003788082926247129659460462172601793592185341287957734218570913345834989073506021404355393802218199263964905227287527043730098365560759171303032685191198709337109427768800315090286880478269055132089734416302064455191741029679806382276824957409921233674716860952588358701357623946504131292729532641423056357018916165650135801711621547809500122867461275373315997341423076112373305671715081307618825141353738979258738320844623051734445651256480092346950377444886604644471088066558448113134178559381767100696435986739483353591480146473561984685169132214906681535804556646[+++]

beta(0)
%19 = 0.2375809024724632975931570104134484867590810055377534726198893919385751544178949333395340493896414265874058610553215106647052057476004312632239759730305903724988350505822127659060244001810496771526834792898470436413854627348062344741800766541510386799572850273625881766731045316881717781376884077104629297745796850622489298177157696740715924505522201335340104258491145231928135946513019751526285542662796319506791371260538978245943968874823927374650933450397200252003238071313253518071332519529765302726989086439398983628581832897877877535591696974241053053623206330489162050396076961506060441217031638048093151172796857184320175795491643132621937621268903072058647815847074925659299113730152378921450929911232876840002420169225419555271117534123275624337359455074230383313687703613616526240346067470689485904450631352357308928108531908127200480336073422071294722670143902549013070236970724521446507905856675203577220922350710987648100335114125423256916248941252806521725577434198559366687155902338519 + 0.0914015925546030014730606778290236333082793068389504132259911445426104166804664779693079675099388861302950360451592473789813354601984899401430480532468820712158281550841024734533911551593106026551662132277066773050792140318549211747008089221344268485579245727742427214148724359229884663331324871544739201087645372177984182730568027126464807774116974358665260800166032216872940602837146027068197900592897963555197795563699033530234133464068864523956743629614065004651033493059194964840869270710178161617809675441126828150974368954311512911309379295983492259332145803850233923844524569761070331532032193571628199858154702158749263665225922403233114321898310677821409327450750545895589556487992546829874535978667939264319268174663128229577657022340777438373002106866318296584170322357518557153799787221688500953744796687284847624166263013588410913447941141348130426153487798196522337622793446136258974003169534569567235301905633392963605504982103509995380854991596366827880655819017457[+++]

beta(z+1) - exp(base*beta(z))/(1+exp(-mult*z))
%20 = (0.E-1002 + 0.E-1002*I) + (0.E-1002 + 0.E-1002*I)*z + (0.E-1002 + 0.E-1002*I)*z^2 + (0.E-1002 + 0.E-1002*I)*z^3 + (0.E-1002 + 0.E-1003*I)*z^4 + (0.E-1003 + 0.E-1003*I)*z^5 + (0.E-1003 + 0.E-1003*I)*z^6 + (0.E-1004 + 0.E-1003*I)*z^7 + (0.E-1003 + 0.E-1004*I)*z^8 + (0.E-1004 + 0.E-1003*I)*z^9 + (0.E-1003 + 0.E-1004*I)*z^10 + (0.E-1004 + 0.E-1004*I)*z^11 + (0.E-1004 + 0.E-1004*I)*z^12 + (0.E-1004 + 0.E-1005*I)*z^13 + (0.E-1005 + 0.E-1004*I)*z^14 + (0.E-1005 + 0.E-1005*I)*z^15 + (0.E-1005 + 0.E-1005*I)*z^16 + (0.E-1006 + 0.E-1005*I)*z^17 + (0.E-1005 + 0.E-1007*I)*z^18 + (0.E-1006 + 0.E-1006*I)*z^19 + (0.E-1006 + 0.E-1006*I)*z^20 + (0.E-1006 + 0.E-1006*I)*z^21 + (0.E-1007 + 0.E-1006*I)*z^22 + (0.E-1007 + 0.E-1007*I)*z^23 + (0.E-1007 + 0.E-1007*I)*z^24 + (0.E-1007 + 0.E-1007*I)*z^25 + (0.E-1007 + 0.E-1008*I)*z^26 + (0.E-1009 + 0.E-1008*I)*z^27 + (0.E-1008 + 0.E-1008*I)*z^28 + (0.E-1008 + 0.E-1008*I)*z^29 + (0.E-1009 + 0.E-1009*I)*z^30 + (0.E-1009 + 0.E-1011*I)*z^31 + (0.E-1009 + 0.E-1009*I)*z^32 + (0.E-1009 + 0.E-1009*I)*z^33 + (0.E-1010 + 0.E-1010*I)*z^34 + (0.E-1012 + 0.E-1010*I)*z^35 + (0.E-1010 + 0.E-1011*I)*z^36 + (0.E-1011 + 0.E-1011*I)*z^37 + (0.E-1011 + 0.E-1011*I)*z^38 + (0.E-1011 + 0.E-1012*I)*z^39 + (0.E-1012 + 0.E-1011*I)*z^40 + (0.E-1012 + 0.E-1012*I)*z^41 + (0.E-1012 + 0.E-1012*I)*z^42 + (0.E-1013 + 0.E-1012*I)*z^43 + (0.E-1012 + 0.E-1013*I)*z^44 + (0.E-1013 + 0.E-1013*I)*z^45 + (0.E-1014 + 0.E-1013*I)*z^46 + (0.E-1013 + 0.E-1014*I)*z^47 + (0.E-1014 + 0.E-1014*I)*z^48 + (0.E-1014 + 0.E-1014*I)*z^49 + (0.E-1014 + 0.E-1015*I)*z^50 + (0.E-1015 + 0.E-1015*I)*z^51 + (0.E-1015 + 0.E-1015*I)*z^52 + (0.E-1015 + 0.E-1015*I)*z^53 + (0.E-1016 + 0.E-1015*I)*z^54 + (0.E-1016 + 0.E-1016*I)*z^55 + (0.E-1016 + 0.E-1016*I)*z^56 + (0.E-1017 + 0.E-1016*I)*z^57 + (0.E-1016 + 0.E-1017*I)*z^58 + (0.E-1017 + 0.E-1017*I)*z^59 + (0.E-1018 + 0.E-1017*I)*z^60 + (0.E-1017 + 0.E-1019*I)*z^61 + (0.E-1018 + 0.E-1018*I)*z^62 + (0.E-1018 + 0.E-1018*I)*z^63 + (0.E-1018 + 0.E-1019*[+++]


Still good convergence, even at 300 iterations as opposed to a thousand.

For a thousand iterations I also tried \(-1E13\) which is super damn slow; but it does work too:


Code:
\r beta.gp
init(1,log(1E13)+Pi*I,1000)

 *** _/_: Warning: increasing stack size to 16000000.
%18 = (-53.31037925066047495673165268607566441060365320209951830282670512703518311905332670954897290121003340367347357576638427942737937756655593614601607209759121030827503565619841325761556391154604610468510111965458382814985131009223932810190407029070225046430545584912318250790448362245942045049589331809730923269574870470808442360621205470709671079952557682950082377712860589176605123968802154554734000105549388030404295316238939643391885358072412563342930139553870241956852147318635128124613345132482589609663508679636901029548496969223908804339500375971626672237476164305355270359838440298473570362628525868412276194237242950046140483531073862807263539616812016414375959857346896994961152631401213145192600901338040934890407376745125523095576228691417792767330796837166899072370248841196971299551592644226081860927266078051497827472465470925766117713227577958701379764648555273059609762185926282045081233463183367564336086542437082503942918649096826001301885423724496810234803512440043964146286728517128 + 7.360266450946606755625339770333231845245059316767878834707669433349582579698705679375088260495642617530138134733551116609406241839542768326904283548473193366268015016236391417670521530789415025484177693337625047940864134806104301477874738357730591534309267298242545400362573090174920086990930087883201651066035998874856241974667003733583794984431919667503280401579565890660180885110352758965608649621892896628823826387686651376173038190006643295198267568951320772835250914368680685144195847990332390454391664023197210059921009043869594981012419398126609816378029130401222839254538445489315570569158347806383311635394703364574744427001475653431583018626887827292355366900932956410596875556787885032085517908966247663803954384614231433279941473399453185838093758720609524468331781270517531376035978375037197341661166859383409145433415621020965772586879920235580416461369413113234746973780911738844491642489800874273806242745638250827972967975133116570641137577661640280561683165401241[+++]

beta(0)
%19 = 2374786044089840508.270373732865472285161792703072583005034504320194897296670573110837203240279256081603942183319086677183028720843243531229080010474875678012148164186407880707264009247341200758940123967501889134191088819836203819151942790043384826476009729913001256798782503297239819612701552141094212367233331987156005900798669827615011526079851801418585799459663265262065925001088311871574944475351457536161876312855082668765883319410744297287166301817905127131824786913560241493155729102734137130829472327012483773922021894397483083518132348322081855704229075884480068444292825646493944435428204498018092081992912750648714796294317067892154584099765754346599471091643393589821244659627753355167664220649837539570592103625993817252995195926049446520380000176743009232682257740186300752443747231498644777960983344214054213595393039498642586066617782041493170862407846964185575572988554713651335008417734348579556114781395708037760841032713748786400309843845537758122524885122150228658261517857919834 + 4103623123749473973.77728961531082338601381620270223050426065179658586676471486781023594905770724546208806728913012470253528330712440772348740692386065753947275211882773979185553712127352488560584076021548247602435327719315128445422846410838075144506147848173745705489759100070528788111089114078298687234615770483038268330317730680651015174044978417912556449706058880110023542141150933432447054585877303105295951859118461159487083443343032691616075402317101699240702237036638782629937777499675331913132106350591130331295590070392742833578660053346373961233824343131598078636100549664866772994222781709660482396108992013277206912876928659542609210140342933860308136321735405671588789826106094862856327524425212212835254195036686261387010949756552535112210452939802962300058237302499026159029271324620999032863078078327531539208025619546338237108521308011704072267286403155882050199810730426205621810436995668027051933842025940389759417587400088586359661074532932782240888482666250711293[+++]

beta(-1)
%20 = 1.576927162543843683068676760531718814822676338730656516858579136595788492336132800688293070762318508803138981429985818207717876685777173540104705735493304044602143662714041753915901499441871830797655458287381942237208238006028239196034539114521063996187434879456085514663475002603080289341187107347379136418718491622433949286386943489133450506037351512496306100716860422064673398852077728896733104048944816918756931635901605002968459407626434986399542103024780503455698037774609695784019103816792650864238081070496134250435841850684175060109760834843284449877884593909003311744000138384827209182731737328621450698785092722445774104906417562212910767991147633060421070587927783404796862485803332925874247439338578443863571197868749406043782778201644845953260106098970969834226568228710767682072090896343931733216100371833233703348527813026390577088844355856550462352053325103816786875145210473159004521311146503879351667580014866187239592247699557138608304072426314741198659815901269899955587941507821 + 0.91896866246456071337594185222758607751752647337614380119720677653580272914954942654699823210612636646678742823800966153758960585768562198708046128351172038047209266517745169324938203255244932413360323056951736133483210002582399249115831421733469902532555663262519396684115822251219309063861779847348494904983356350175166765104559202284566339520452103462607779906833212116763992784055947994757762915392633079210177899853383809859777735039269561791035667012008461589924735530411927153705866644238669553801206045657130084494295175351029908889739292137063644831833949990685958384429820159378175373542791410364485183699889572233145669015140271491329016767271717181663979721485668418543142789692030876826854801072945975232474794780933726134912039585800265903628995121213980072187330836497064185989816381753518631788889033816066079032476399083457939758032760305694674429287839139838697683600154515082462556644226036616469952855715518373530609971769339341771115734711654580087267671583295840[+++]

beta(z) - exp(base*beta(z-1))/(1+exp(-mult*(z-1)))
%21 = (0.E-983 + 0.E-983*I) + (0.E-981 + 0.E-980*I)*z + (0.E-978 + 0.E-978*I)*z^2 + (0.E-976 + 0.E-976*I)*z^3 + (0.E-974 + 0.E-974*I)*z^4 + (0.E-972 + 0.E-972*I)*z^5 + (0.E-970 + 0.E-971*I)*z^6 + (0.E-969 + 0.E-969*I)*z^7 + (0.E-967 + 0.E-967*I)*z^8 + (0.E-966 + 0.E-965*I)*z^9 + (0.E-964 + 0.E-964*I)*z^10 + (0.E-962 + 0.E-963*I)*z^11 + (0.E-961 + 0.E-961*I)*z^12 + (0.E-960 + 0.E-959*I)*z^13 + (0.E-958 + 0.E-958*I)*z^14 + (0.E-956 + 0.E-957*I)*z^15 + (0.E-955 + 0.E-955*I)*z^16 + (0.E-954 + 0.E-953*I)*z^17 + (0.E-952 + 0.E-952*I)*z^18 + (0.E-951 + 0.E-951*I)*z^19 + (0.E-950 + 0.E-950*I)*z^20 + (0.E-948 + 0.E-948*I)*z^21 + (0.E-948 + 0.E-947*I)*z^22 + (0.E-946 + 0.E-946*I)*z^23 + (0.E-944 + 0.E-945*I)*z^24 + (0.E-943 + 0.E-943*I)*z^25 + (0.E-942 + 0.E-942*I)*z^26 + (0.E-941 + 0.E-941*I)*z^27 + (0.E-939 + 0.E-940*I)*z^28 + (0.E-938 + 0.E-940*I)*z^29 + (0.E-937 + 0.E-937*I)*z^30 + (0.E-936 + 0.E-936*I)*z^31 + (0.E-935 + 0.E-934*I)*z^32 + (0.E-933 + 0.E-934*I)*z^33 + (0.E-932 + 0.E-935*I)*z^34 + (0.E-931 + 0.E-931*I)*z^35 + (0.E-930 + 0.E-930*I)*z^36 + (0.E-929 + 0.E-928*I)*z^37 + (0.E-928 + 0.E-928*I)*z^38 + (0.E-926 + 0.E-927*I)*z^39 + (0.E-925 + 0.E-925*I)*z^40 + (0.E-924 + 0.E-924*I)*z^41 + (0.E-924 + 0.E-923*I)*z^42 + (0.E-922 + 0.E-922*I)*z^43 + (0.E-921 + 0.E-921*I)*z^44 + (0.E-920 + 0.E-920*I)*z^45 + (0.E-919 + 0.E-919*I)*z^46 + (0.E-919 + 0.E-917*I)*z^47 + (0.E-917 + 0.E-916*I)*z^48 + (0.E-915 + 0.E-916*I)*z^49 + (0.E-914 + 0.E-915*I)*z^50 + (0.E-913 + 0.E-913*I)*z^51 + (0.E-913 + 0.E-912*I)*z^52 + (0.E-912 + 0.E-911*I)*z^53 + (0.E-910 + 0.E-910*I)*z^54 + (0.E-909 + 0.E-910*I)*z^55 + (0.E-908 + 0.E-908*I)*z^56 + (0.E-907 + 0.E-907*I)*z^57 + (0.E-907 + 0.E-906*I)*z^58 + (0.E-905 + 0.E-905*I)*z^59 + (0.E-904 + 0.E-904*I)*z^60 + (0.E-903 + 0.E-905*I)*z^61 + (0.E-902 + 0.E-902*I)*z^62 + (0.E-901 + 0.E-901*I)*z^63 + (0.E-901 + 0.E-900*I)*z^64 + (0.E-899 + 0.E-899*I)*z^65 + (0.E-897 + 0.E-898*I)*z^66 + (0.E-897 + 0.E-897*I)*z^67 + (0.E-896 + 0.E-896*I)*z^68 + (0.E[+++]

And it still works; though I suspect 1000 iterations is the key again.




Either way, I don't see the errors you are talking about. But remember I'm running \(\exp(bz)\) as opposed to \(b^z\); whereas my old code ran with the latter. It fixes a good amount of issues.

PS: I think I figured out how to solve the normalization process; it requires renormalizing each step of the way. So that every \(F_n(0) = 1\) including \(F_0(z) = \beta(z+k_0)\). So in reality, we want to run the program \(F_n(z) = \log^{\circ n} \beta(z+n+k_n)\). I'm just trying to find an efficient manner at the moment. This solves the problem of runaway normalization constants for multipliers and bases; where the final normalization constant can move in the thousands by doing slight adjustments to the code.


Regards, James
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RE: A first hires look at tetration \(\lambda = 1\) and \(b = e\) - by JmsNxn - 10/25/2021, 06:07 PM



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