Cloud Cosmology : Building the Web Interface for iCosmo

0.4 MB·English

by  Thomas Kitching

Astronomy&Astrophysicsmanuscriptno.paper (cid:13)c ESO2009
January22,2009
Cloud Cosmology : Building the Web Interface for iCosmo
T.D.Kitching1,A.Amara2,A.Rassat3,A.Refregier3
1 OxfordAstrophysics,DepartmentofPhysics,KebleRoad,Oxford,OX13RH,UnitedKingdom
2 DepartmentofPhysics,ETHZurich,Wolfgang-Pauli-Strasse16,CH-8093Zurich,Switzerland
9 3 IRFU-SAP,Serviced’Astrophysique,CEA-Saclay,F-91191GifsurYvetteCedex,France
0
0 Submitted:January22,2009
2
ABSTRACT
n
a
J Aims.Astronomy and cosmology have embraced the internet. We routinely and successfully use the internet as a repository for
sharing code, publications and information, and as a computational resource. However the interactive nature of the web, for use
1
as an alternative to downloading code has been largely overlooked. In this articlewe will outline a simple framework in which a
2
cosmologicalcodecanbeturnedintoaninteractivewebinterface.Thisispresentedasaresultofcreatingwww.icosmo.orgwhich

isafront-endfortheopen-sourcesoftwareiCosmo.
]
M Methods.WeexplainhowanHTMLpagecanbecreatedandhowacosmologicalcodecanbeincorporatedintoawebenvironment
usingCGIscripts.Weoutlinehowplotsanddownloadabletextcanbemade,anddescribehowhelpanddocumentationcanbecreated.
I Results.ByusingsimpleHTMLandCGIscriptsabasicwebinterfaceforanycosmologicalcodecanbecreatedeasily.Weprovide
.
h aworkedexampleofthemethodsoutlined,whichcanbeusedasasimpletemplatebyanyresearcherwhowantstosharetheirwork
p online.
-
o Keywords.cosmology–observables–numericalmethods
r
t
s
a 1. Introduction tionalfarm(asourceofCPU’sorpeopleusedforaspecificsuite
[
ofproblems),orasasimplerepositoryfordataorcode,towards
Theinternethasbeguntorevolutionisethewaythatastronomi-
1 amodeinwhichtheinteractivityoftheinternetisharnessedto
calresearchisconducted.Onlinepaperarchives(e.gthearXiv1)
v maketheactofperformingusefulcosmologicalcalculationsan
have allowed for the dissemination of articles and results, and
3 online,interactiveexperience.Cloudcomputingisthetermthat
4 data(e.g.SDSS2 Adelman-McCarthyetal.,2006)areroutinely isgiventotheprocessofusinganon-localanonymousmachine
1 made publicly available online for anyone to analyse. We of toperformcomputationaltasks.Wecalltheonlinecomputation
3 course use the internet to communicate via email, voice and
ofcosmologicalproductscloudcosmology.
. video connections.More recently there have been some efforts
1
tousetheresourcesoftheinternettoaidinthecalculationofa Cosmological calculations were originally done using sim-
0
9 specificsuiteofscientificresults;forexampletheGalaxyZoo3 ply paper and pencil. The advent of the computer made more
0 (Lintottetal.2008)andcosmology@home4bothofwhichsolve complexcalculationsquickerandeasier to compute.Theinter-
: particular problems of concern for the authors and simultane- nethasenabledcodetobesharedbetweenthecommunity,and
v
ouslyserveasremarkableoutreachprogrammes. the next step in this evolution is so create an interface for the
i
X The open source code made available through the internet codeitselfontheinternet.
hasenabledcosmologiststousethiscode,savingtheirtimetodo
r The danger in creating web-interfaces for complex code is
a furtherresearch.OfparticularnotearetheCMBpowerspectrum
that a ‘black box’ mentality is encouraged. In this article we
codesCMBfast(Zaldarriaga& Seljak, 2000)and CAMB (Lewis
strongly advocate the opposite approach and work within the
et al., 2000) and some likelihood analysis codes for example
philosophythateverythingcreatedshouldbea‘transparentbox’
COSMOMC(Lewis&Bridle,2002)andBAYESYS5.
by which we mean that the code powering the site should al-
Howevertherehavebeenrelativelyfewonlineresourcesthat
ways be made available and thatdocumentationexplainingthe
cosmologistscanuseintheirresearchasareplacementtodown-
calculationsandthecodeshouldbeprovided.
loadingcode.NotableandexcellentexceptionsincludetheCMB
LAMBDA6toolbox,andtheimpressiveonlinedatareductionin- The aim of this article is to guide the reader through the
terfaceAstroWISE7,therearealsosomebasiccosmologycalcu- process of turning an open source code into a web interface.
lators(e.g.Wright,2006).Theuseoftheinternetinthisfashion This will be done within the context of presenting the interac-
heralds the move away from using the internet as a computa- tive tools on http://www.icosmo.org that we have created
as a front-end web interface for the open source code iCosmo
1 http://arxiv.org/ (Refregier et al., 2008). The website allows cosmological dis-
2 http://www.sdss.org/ tances, Hubble parameter, growth factor, linear and non-linear
3 http://www.galaxyzoo.org/ matter power spectra, cosmic shear power spectra, baryon dis-
4 http://www.cosmologyathome.org/ tancescales,supernovaemagnitudedistances;andlensing,BAO
5 http://www.inference.phy.cam.ac.uk/bayesys/ and supernovaeFisher matricesto be calculated onlinein real-
6 http://lambda.gsfc.nasa.gov/toolbox time. In addition to the interactive web pages, there are links
7 http://www.astro-wise.org/ to the open source iCosmo code and to some tutorial/teaching
2 T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo
resources for cosmology and the probes used to measure cos- it is the web browser that does the compiling when a particu-
mology. lar page is loaded. HTML pages can be created in most word-
In this article, we will notdescribe all possible ways thata processing or text based programmes (e.g. MS Word, Emacs,
webinterfacecouldbecreated.Wewillpresenttheprocessfrom etc.) and just save the file with the extension.html.The web-
theperspectiveofcosmologists(whoarenotexpertsinwebde- pagecan then be viewedby typingin the path to the file. Note
sign)whowanttomaketheircodeeasilyaccessibletoawideau- that when a browser calls a webpage it does so as an exter-
dienceandwantaneasyandquickwaytomakecodeavailable. nal user, so permissions on any files need to be such that a
Wewillbeginbydescribingtherequirementsthataworkingcos- global user can execute the HTML code (e.g. in UNIX using
mologistmay needfroman interactivewebinterface.Then we the chmod command). In general one must be careful about
will describe the particular solution that we have used, along permissions, if a file is writable by a global user then a mali-
withsomealternativesthatwehaveinvestigatedalongtheway. cious user could turn such a file into a virus. However if a file
Thiswillbewritteninapedagogicalstylefromthepointofview is writable but not executable this makes such an attack much
ofanon-expertincomputerscience. moredifficult,indevelopingiCosmowefollowedtheguidelines
TheiCosmoHTMLandCGIwillbereleasediniCosmov1.2 set out on this webpage http://www.oucs.ox.ac.uk/web/
(http://icosmo.pbwiki.com). A description of the interac- faq/index.xml.ID=safeperl.
tivefeaturesofthewebsitearegiveninAppendixA. AverysimpleHTMLpageisshownhere:
<HTML>
2. Websolutions <head>
<title>Hello World</title>
The needs of the cosmological community are not entirely
</head>
unique to science but are fairly representative in terms of the
<body>
types of productthat are required from a useful web interface.
<font color="yellow">
We willexplainthe requirementsthatwe needas cosmologists
Hello World
andthenstepthroughthesolutionsthatwehavefound.
</font>
</body>
2.1.RequirementsfromCosmology </HTML>
Tobeatruereplacementtodownloadingcodethewebinterface
The first line declares that this is an HTML code, and the
mustbe able to performthe majority of the actions, and create
lastlineistheendthecode.Theheadcontainsinformationthat
alltheproducts,thatonemaywishtomakeusingthecode.
will not appear on the page itself but may affect its attributes.
Ausermustbeabletochangetheinputseasily.Incosmology
The body contains information that will appear on the page,
these are commonly values of cosmological parameters. There
here there is a simple style change made to the font of the
arealsosomenumericallimitsandresolutionsofparticularvari-
text shown. We have found that the following pages were
ablesonwhichcosmologicalfunctionsdepend;forexamplered-
particularlyusefulindocumentingtheHTMLsyntax
shiftz,wavenumberk,azimuthalwavenumberℓ.
The two most useful end-point products are the plot (or – http://www.w3schools.com/html/DEFAULT.asp
graph)thatcanbeusedtovisuallyrepresentsomefunctionalbe- – http://www.htmlgoodies.com/
haviour,andatableofthedatainthegraphinaformatthatcan – http://www.htmlcodetutorial.com/
thenbeusedinsubsequentprogrammes.Thegraphicalinterface – http://en.wikipedia.org/wiki/HTML
should be flexible enough that any aspect of the graph can be
though this is by no means an exhaustive list and typing in
tailoredonline to the users needs.In cosmologywe often need
HTMLand a problemintoanysearchengineusuallyresultsin
toplotfunctionsformultiplevaluesofcosmologicalparameters
findingthesolutionveryquickly.TocheckthattheHTMLpage
includingerrorbars.
thatyouhavewrittenisvalid(nobugs)thereisanonlineHTML
The iCosmocode (Refregieret al., 2008)is a low-redshift,
compiler that will highlightany problemsor inconsistenciesat
darkUniverse,cosmologytoolthatallowsa userto createcos-
http://validator.w3.org/– to use this the website needs
mologicalfunctions,observablesandparameterforecastsforar-
tobeonline.
bitrarycosmologiesand experimentaldesigns. Our task was to
Writing‘bare’HTMLallowsthewebpagetobeexactlytai-
turnthisintoaninteractivewebinterface.
loredtoyourneeds,howeveritisatimeconsumingactivityand
A simple demonstration of the procedures covered in this
thesyntaxneededtocreatecomplexdisplayscanbecomecum-
Sectionareshownon
bersome.Thankfullytherearesomeverygoodwebsitecreators
– http://www.icosmo.org/WebPaper.html availablethatallowwebsitestobecreatedinmuchthesameway
– http://www.icosmo.org/cgi-bin/WebPaper.cgi thata“PowerPoint”(orKeynote)presentationismadee.g.cre-
atingtexboxes,changingfontsandcolours,addingpicturesetc.
andinAppendixB,theseexamplescanbeusedasatemplateto ForthefrontendoftheiCosmositeweusediWebforMacOSX,
createnewcosmologicalwebinterfaces. forWindowsthereisFrontPage,andthereareevenonlineweb-
pagecreatorssuchasGoogleSites.
To enable moreadvancedfeaturesin a webpageone has to
2.2.HTML
usescripts.Therearedifferenttypesofscript,thosethatcanbe
HTML(HyperTextMarkupLanguage)isthelanguageinwhich run within HTML itself and those that cannot. In iCosmo we
web pagesare written. A website consists of a groupof pages, haveusedsomein-HTMLJAVAscriptstoenablesomeadvanced
usually in some directory structure. HTML is akin to the fa- features,forexamplethetabbedenvironment(seeAppendixA)
miliar Latex typesetting language in which a script is written and some more simple things like allowing all checkboxes to
and then compiled to create a document. In this case however be selected at once (see Section 2.6). These in-HTML scripts
T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo 3
are defined in the <head> section of the HTML and are ini- </head>
tialised using <script language=javascript> and ended <body>
using </script>, there are many open-source javascript wid- <font color="yellow">
gets which can be copied and pasted from the web into any Hello World
HTMLpage. </font>
HTML
#this is a comment
2.3.RunningScripts
#do a simple calculation in PERL
$x=2*2+2*2*2;
In creating a web interface for cosmology one will inevitably
#display the calculation on the webpage
have to run some sort of programme that will take inputs (say
print<<HTML;
cosmologicalparameters) and performa cosmologicalcalcula-
2²+2³=$x
tion.Runninganexecutable,orscript,canbedoneeitheronthe
HTML
sideoftheserver(wherethewebpageisstored,seeSection2.4)
#end the HTML
orcanbedonethroughthebrowseritselfonthe‘client’side.We
print<<HTML;
opted for, and recommend,the server-side approachsince cos-
</body>
mologicalcalculationscanbecomplex(aclientscomputational
</HTML>
powermaybeminimal)andserversidescriptsaresaferforthe
HTML
client(theydonotneedtoruna potentiallydangerouscodeon
exit;
theirpersonalmachine).
There are a number of ways which we encountered that
allowscriptstoberun.MostsimplyanyCcodecanbecompiled
which can be run in a browser by typing the executable name
The first line declares that this is a PERL script. The
into the command line, though creating an entire webpage out
print<<HTML then says “the following is HTML” where
of a C code quickly becomes complex. Alternatively one can
use JAVA8 and then create a “Applet” (althoughthis is a client the header is created. Calculations can then be done in PERL
anddisplayedon the webpage,in thisverysimple examplewe
side solution). Other alternatives include PHP and API which
calculated 22 + 23. We also show here an example CGI shell
areadditionstoHTMLthatallowscriptstoberunfromwithin
HTML. An example C code, compiled like gcc test.c -o script:
test.cgiisgivenbelow:
1 #!/bin/sh
2 # xmltest.sh
1 #include <stdio.h>
3 # XML-based "Hello World"
2 int main(void) {
4 echo Content-type: text/xml
3 float p,q,r;
5 echo
4 p=2.*2.;
6 echo "<?xml version=\"1.0\"
5 q=2.*2.*.2;
encoding=\"UTF-8\"?>"
6 r=p+q;
7 echo "<message>"
7 printf("Content-Type: text/plain;
8 echo "<text>Hello World!</text>"
charset=us-ascii\n\n");
9 echo "</message>"
8 printf("Hello world\n\n");
10 exit 0
9 printf("2*2+2*2*2=%f\n",r);
10 return 0;
11 }
The easiest solution that we have found is to use CGI
2.4.Servers,URLs,IPAddresses
(Common Gateway Interface) scripts. These are executable
scripts(akintoamorecomplicatedversionofashellscript)that A webpage is hosted on a server which, as far as we are con-
canbewritteninavarietyofdifferentcodelanguages.Whena cerned, is essentially a computer with some specific software
CGI script’s URL is called the server runs the CGI script, that installedthatallowsCGIscriptstoberun,andonwhichtheweb
createsawebpagewhichisthendisplayed.Themostcommon site resides. When you click on the URL of any webpage the
language in which CGI scripts are written, and the one which browserwillberedirectedtoaserver,forasimplewebpagethe
we have chosen for iCosmo, is PERL9. For iCosmo we chose browserwilldownloadthewebpageHTMLfromtheserverand
PERL over Shell scripts because PERL is a full programming displayit,foraCGIscripttheserverwillrunthescriptandthen
language with many available libraries, and as such is some- sendthe HTML createdto the usersbrowser.Serversarenoth-
whatmoreflexible.AnexamplePERLCGIscriptisshownhere: ingmorethananormalcomputerswithextrasoftwareinstalled,
indeedevena laptopcan becomea server(thisis actuallyvery
#!/usr/bin/perl easywithsomerecentoperatingsystemse.g.MacOSXLeopard,
print<<HTML; where serversoftware is includedas standard).The most com-
<HTML> monformofserversoftwareisApache10.Awebpageonaserver
<head> typically consists of a number of folders : one containing the
<title>Hello World</title> staticpages(frontpageofwebsiteetc.),onecontainingtheCGI
scripts,onecontainingsomesharedfiles.
8 http://java.com/en/
9 http://www.perl.com 10 http://www.apache.org/
4 T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo
ForiCosmowedevelopedthesiteusingApacheinstalledon print<<HTML;
aMacBooklaptop,toturnthelaptopintoaserveralloneneeds <HTML>
to do is turn on “web sharing” once Apache is installed. Later <head>
wetransferedthesitetoadedicatedserver. <title>Hello World</title>
Every computer and every server connected to the inter- </head>
net has a unique numerical indentifier called an IP (Internet <body>
Protocol) address. To connect to a servers website from a <font color="yellow">
browser the IP address of the server needs to be known. The Hello World
keythingtorealisehereisthatIPaddresses(computers/servers) </font>
useports,throughwhichtheycommunicate.Whentwocomput- HTML
ers interact the IP address says where the machine is, the port #this is a comment
sayswhattypeofinteractionwilloccur.HTML webpagesuse #do a simple calculation in PERL
port 80. So the server needs to have port 80 open to allow IP $x=2*2+2*2*2;
addressestoaccessesHTMLpagesstoredontheserver. #display the calculation on the webpage
If a computer is connected to a network then it may have print<<HTML;
an internal IP for the network and the router will have an ex- 2²+2³=$x
ternalIPaddress.Whendevelopingawebsiteathome,through HTML
arouterforinstance,therouterssoftwareshouldbechangedto
openport80.Thereisa veryusefulwebsiteherethatwillpro- use IPC::Open3;
videastep-by-stepguidetodothisforalmostanyrouteravail- $ENV{’PATH’} = ’/Applications/itt/idl70/bin/’;
ablehttp://www.PortForward.com,therouterthenneedsto $progName = "idl";
re-routeanyincomingtrafficthroughtheportto theinternalIP open3(WRITEIDL,READIDL,ERRORIDL, $progName);
of the machine. Once port 80 is open then typing in the exter- print WRITEIDL "x=2ˆ2+2ˆ3+2ˆ4 \n";
nal IP to a web browser will take the browser to your servers print WRITEIDL "print,x \n";
webpage. $y =<READIDL>;
AURL(UniformResourceLocator)isanalpha-numericre- print<<HTML;
placement for an IP address. When developing a website you 2²+2³+2⁴=$y
will be able to use the IP as an address for the webpage e.g. HTML
typing http://193.168.0.1will take you to your webpage. #end the HTML
If you want to create a URL instead of using the IP address print<<HTML;
then DNS (Domain Name System) server can be used which </body>
will reroute any traffic using a given URL to your IP address. </HTML>
There are a number of free services that do this, when de- HTML
veloping iCosmo we used DynDNS www.dyndns.com which close(WRITEIDL);
is a dynamical DNS server. Dynamical servers are particu- close(READIDL);
larly useful if your IP address may change over time, this is close(ERRORIDL);
almost always the case for a home computer that is linked exit;
to the internet via an ISP (Internet Service Provider). Later,
once your website is at a mature stage more suitable domain
namescanbebought,foriCosmoweusedthecommonservice
http://www.123reg.com. In this example an IDL script is initialised by the Open3
command, when the command WRITEIDL is called (which is
named as the inputto the IDL) actual IDL commandlines can
2.5.LanguageChoice
be entered which can then be read back into the PERL script
using READIDL. The result can then be printed into an HTML
Whendevelopingawebinterface,andanopensourcesoftware
package,thechoiceofacodinglanguageisimportant.iCosmo pageintheusualway.Notethatanycodepackagecouldberun
inthisway,weuseIDLasanexample.
iswritteninIDL,whichimmediatelycreatedsomeobstaclesto
creatinga web interfacesince IDL cannotbe run directlyfrom
within a CGI script. Languages which are more conducive to
web interface programming are C (which can be run directly
within a browser), JAVA, PERL and python. One option for You may want to run some code on a machine that is
iCosmowasthereforetore-codethe entirepackageintosome- not the server. For example this may occur if you cannot in-
thinglikeJAVAorC,howeverthiswouldhavemeantlosingthe stall some particular library or if more computing power is
featuresforwhichwechoseIDLinthefirstplace–easysyntax, needed. The IPC::Open command can be used so that when
vastscientificlibraries,easyplottingroutines. a particular CGI script is run the server can ssh into a ma-
When developing iCosmo we found a way to call any chine that has the required software, perform the calcula-
programme from within a PERL CGI script. IPC::Open311 (or tion on that machine and then output the results to the web-
Open2) creates a “child” process from the main PERL script page. This is done by stacking the commands on the $prog-
whichthenruns(onthecommandline)andcanreturnvaluesto Name line e.g. $progName = "ssh server@machine ’cd
thePERLscript.Anexampleisgivenbelow: WebServer/CGI-Executables; command’" which connects
toamachineundertheusernameserver,changesdirectorytothe
#!/usr/bin/perl CGI folder and then runs some command. Most servers should
come with some common software already installed, although
11 http://www.perl.com/doc/manual/html/lib/IPC/Open3.htmlinstallingsomecomplexastronomicalsoftwaremaybedifficult.
T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo 5
2.6.InputandOutput pgscr(0, 1.0, 1.0, 1.0);
pgscr(1, 0.0, 0.0, 0.0);
We have now outlined how to create a simple webpage and a
CGIscriptthatcanrunaparticularcosmologycodeandoutput
pgsci($linecolour);
resultstoawebpageinatextformat.Herewillwilldiscusshow
pgline($number, @x, @y);
inputscanbetakenfromawebpageandputintoaCGIscript.
pgend;
The key to web interactivity is the HTML form. Forms
allowawebusertoinputinformationintoawebpagewhichcan
thenbereadbytheserver.Youwillfindformsonalmostevery
This would create a gif showing the data in the arrays @x
web page (from online shops to airline bookings). A form is
[email protected]
basically a set of inputs and a ‘submit’ button (forms can also
canbeused
be automatically submitted – using javascript) when a form is
submittedanewscriptisrunwhichisgiventhevariablesinput
<img src="icosmo plot.gif" width="500px" alt=""/>
asarguments.Thefollowingexamplewouldcreatesomeboxes
inwhichnumberscouldbeinputandthensentto thenewCGI
script.
To create a downloadable text file the following PERL
syntaxwouldwritethestructures$xand$ytoafile
<form action="cgi-bin/newscript.cgi" >
<input type="text" name="omega m" size="5"
$file="file.txt";
value=0.3>
open (MYFILE, $file);
<input type="text" name="omega de" size="5"
for($start=1;$start<$number;$start++){
value=0.7>
<input name="submit" type="submit" value="Begin
$valueF=$x[$start];
Calculations">
printf MYFILE "$valueF";
</form>
$valueF=$y[$start];
printf MYFILE "$valueF \n";
The variables omega m and omega de are submitted to
}
newscript.cgi(the variablescan be seen in the URL delim-
ited by &’s or can be hidden using METHOD=“POST” in the
ThefollowingHTMLwouldcreatealinktofile.txt
firstline).Therearemanytypesofforminputthemostcommon
are
<a href=’file.txt’> Download Text Output</a>
– text:inputatextvalue,numericaloralphabetical
– checkbox:atick-boxwhichcantakeoneoftwovaluesde-
pendingonwhetheritisselectedornot
– radio:anexclusive‘or’i.e.valuecantakeanumberofdif-
2.7.BrowsersandStyling
ferentvalues
– select:adrop-downboxiscreatedwhichgivesanumberof
When creating a web interface one must always be care-
exclusiveoptions
ful with respect to browser compatibility. Issues can arise
from even simple things such as choosing a font such that
Thereisextensiveonlinehelpforallthesetypesofforminput.
it will appear the same in each browser (we found this
In iCosmoto read form data into a CGI script we used the
website particularly useful http://dustinbrewer.com/
ReadParsePERLcommandwhichworksinthefollowingway
fonts-on-the-web-and-a-list-of-web-safe-fonts/,
there are only a handful of fonts available) to an entire page
&ReadParse(*input);
appearingincorrectly.
$omm = $input’omega m’;
Incompatibility issues are usually created when obsolete
$omv = $input’omega de’;
HTML methods are used, this means that some new browsers
will not recognise certain HTML commands and will render
them in a differentway than intended. The most up-to-date(c.
which would read in the submitted variables from above
2008)standardforwritingbrowser-proofHTMListousestyles.
intothenewPERLscriptasthevariables$ommand$omv.
TocreateplotsusingPERLweusedthecommonPGPLOT12 Stylesareessentiallysmallscriptsthatcanbewrittensepa-
software (we installed this foruse in PERL using the excellent rately(intheheader)orwithincertainbasicHTMLcommands
astronomical suite of tools provided by SciKARL13). Within thattell the browserhow to renderthe objectin question- that
PERLaplotcaneasilybecreatedusingthefollowingsyntaxor couldbesometext,atable,animageetc.Ansimpleexampleis
similar givenbelow
#Create a graph: <a href="http://www.icosmo.org"><font
$ENV{’PGPLOT PS BBOX’} = "MAX"; color="#66000">iCosmo</font></a>
pgbegin(0,"icosmoplot.gif/gif",1,1);
pubplot($xmin,$xmax,$ymin,$ymax,0); <a style="color: #660000"
#black-on-white plots: href="http://www.icosmo.org">iCosmo</a>
12 www.astro.caltech.edu/∼tjp/pgplot/
13 http://astronomy.swin.edu.au/∼karl/SciKarl These two lines ostensibly do the same thing (create a red
6 T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo
coloured hyperlink to iCosmo) but the first line does not use Finallyvideo(oraudio)tutorialscanbeprovidedinaddition
stylesandassuchmayappearincorrectinsomebrowsers. totextbasedandinteractivehelp.Videotutorialscanallowthe
Other problemscan occurif, for example,a tableswidth is web site to be demonstrated to the user and for all the aspects
definedin%,whichsomebrowsersrecognise,whereasitshould of the site to be presented. For iCosmowe choose YouTubeto
be defined in terms of pixels (px). When writing a web in- host the videos online - YouTube also allows videos to easily
terface you should constantly check that whatever changes are be embedded directly into HTML. Alternatively you can host
made are accurately reproduced in all browsers. This can be you own videos, or publish audio as a pod-cast. To record on-
donemanuallybyinstallingsomeofthemostcommonbrowsers screen video and audio there are many cheap software options
(Firefox, Opera, Safari, Internet Explorer) or by using an on- available;wechoseiShowUforMac.
line browser checker - we found this site particularly useful
http://browsershots.org/.
2.10.AWorkedExample
Asaworkedexamplewehaveprovidedsomesimpletemplates
2.8.VersionTracking
ofanHTMLpageandaCGIpageinAppendixB.Workingver-
When creating a web interface keeping track of different ver- sionsofthesecanbefoundon
sions, and what changes have been made is important so that
– http://www.icosmo.org/WebPaper.html
the site can be restored to any point in its creation if thingsgo
– http://www.icosmo.org/cgi-bin/WebPaper.cgi
wrong.Therearemanycommerciallyavailableandopensource
wayswhichcanbackupwebsitesandcode,themostcommonly
In these examples we show how each of the components de-
usedisSVN(SubVersioN).
scribedinthisSectioncanbebroughttogethertocreateasimple
For iCosmo,creatinga web site in collaboration,we found
cosmologyinterface.Weshowhowstylesandformsareusedas
that using a self-made wiki page was the optimalsolution. We
well as some other HTML tricks, for exampleinserting an im-
used the public wiki pages http://www.pbwiki.comand on
age,creatingGreeklettersandmakinglists.IntheCGIexample
our iCosmo wiki page created a “Blockbuster” style table. If
we take some data from the HTML page and use this data to
one personwanted to editthe site they “checkedout” the code
performacalculationusingtheiCosmoIDLsoftware.
(downloadedasazippedfile),andmadeanoteonthewiki.They
Wehaveoutlinedhowtocreateawebinterfaceforcosmol-
would then “check in” and upload a new version. All versions
ogycalculationsfromscratch.Thiscanbedonebythroughthe
are stored on the wiki page and this preventedmultiple people
following3steps:
workingonthesamecodesimultaneouslyaswellassavingthe
oldversionsforbackup. – Create a static HTML site to collect user in-
put. This can be done using the forms discus-
sion in Section 2.2 or the template provided
2.9.HelpSolutionsandDocumentation
http://www.icosmo.org/WebPaper.html.
Whencreatingawebinterfaceforcosmology,andfollowingthe – Write a CGI script to run your program
‘transparentbox’approachthatwehavetakenwithiCosmo,suf- (e.g. an IDL .pro file). This is discussed in
ficientmaterialshouldbeprovidedandlinkstorelevantpublica- Section 2.6, and an example can be found at
tionsmade(attheveryleastlinkstoothersitesthatcontaingood http://www.icosmo.org/cgi-bin/WebPaper.cgi.
materialshouldbeadded). – Create an interface for displaying the results. See
For iCosmo we have made a multi-layered suite of help http://www.icosmo.org/cgi-bin/WebPaper.cgi for
resources. The simplest is to add help directly as text to the anexample
webpages in question. Links can easily be made to publica-
Someusersmaywish to simplyextendthe capabilityofan
tions available on online archives. The next layer is to cre-
existingsite,suchasiCosmo,thiscanbedonebyusingthetem-
ate more information on a different page and make this an
plates provided. The iCosmo website source code will be re-
evolving and interactive document. The most common forms
leasediniCosmov1.2(http://icosmo.pbwiki.com).
of these interactive documents are wiki pages and online
word processors (e.g. GoogleDocs).For iCosmowe have used
http://www.pbwiki.com to create a number of wiki pages
3. OnlineCosmology
that are edited and updated by a group of experts in each field
wehavecovered.TheGREAT08challenge(Bridleetal.,2008; Theinternethasbeenharnessedinastronomyandcosmologyas
http://www.great08challenge.info) has made good use a communicationtool and as a source of processing power for
ofGoogleDocstoprovideonlinedocumentation. individualcalculations.The movetowardsusing the interactiv-
The next layer of interactivity is to provide an online ityoftheinternetadvocatedhereissimilarinmotiveandresult
forum for users of your site to discuss the science, results tocloudcomputingwherecomputationalprocessesarenotper-
and the webpage. In cosmology we are fortunate to have formed locally but within the cloud (remote, anonymous, ma-
http://www.cosmocoffee.info. For iCosmo we have pro- chinesontheinternet).Werefertotheuseoftheinternetinthis
videdadiscussionforumhostedbycosmocoffee. fashion,forcosmologicalcalculations,ascloudcosmology.
Tomakepostingawebsiteontonetworksites(e.g.Facebook, It may appear strange to an expert in web design or cloud
MySpace)andbookmarksites(e.g.Twitter,Digg)easyforauser computingthatweareusingtherelativelywellknownCGIap-
itiscommontoaddsmalllinksatthebottomofapagethatwill proachtowritingwebpagesasanexampleofcloudcomputing.
automatically post to these websites. For iCosmo we used the Howeverthedefinitionofcloudcomputingdoesnotstipulatethe
free service providedby http://www.sharethis.comwhich methodbywhichthecloudiscontacted.Weadvocatetheuseof
providesasnippetofHTMLthatoncepastedintoawebsitecom- CGIscriptsbecauseoftheirsimplicity,easy-of-useandthevast
pressesallthepostinglinksintoonebutton. amountofscientificlibrariesthatareavailableforthem.
T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo 7
Otherrecentsuggestionsforusingtheinteractivityofthein- Acknowledgments
ternettoincreaseproductivityinastronomyandcosmologyare
TDK is supported by the Science and Technology Facilities
3D environmentsand the virtualobservatory.3D environments
Council, research grant number E001114. We thank all the
(e.g.Hut,2007)canbeusedforoutreachactivitiesandasvisu-
iCosmocontributorsFilipeAbdalla,DavidBacon,SarahBridle,
alisationtoolsforcomplexdatasets.Theconceptofthevirtual
AlainGueguen,BenjaminJoachimi,DanielKubas,JustinRead,
observatory (e.g. Szalay & Brunner, 1999) is that astronomers
ShaunThomas,JochenWelleraswellasLucaAmendola,Nabila
canaccessvastlibrariesofpre-observeddata,whereanydesired
Aghanim, Anna Cibinel, Marian Douspis, Robert Feldman,
observationhasahighprobabilityofalreadyexisting,thusmak-
OliverHahn,AlanHeavens,OferLahav,AndyTaylor.Forhelp
ingtheneedforanewobservationredundant.
in comparing Fisher matrix calculations we also thank Jiayu
Wehaveoutlinedtheparticularsolutionsthatwehavefound
Tang, Peter Schneider, Martin Kilbinger, Jan Hartlap, Martin
thatwillenablecosmologiststoturntheircodeintoawebinter-
Kunz and Fransico Castander. For help in hosting the website
face.Lookingaheadweenvisageamovetoamoreopenculture
we thankETH Zurichand AxelBeckertfor invaluableand ex-
ofsoftwaredisseminationwherenotonlyarticlesarepublished
perthelp.
butthecodeusedtocreatethescienceinthearticleisalsomade
public.Herewedefineanumberoftierspossibleofinvolvement
– Asaminimumonecanpublishthecode,relatedtoanarticle,
References
online.
– Secondly the code can be published as part of a coherent Adelman-McCarthyetal.,2006,ApJS162,38
Albrechtetal.,2006,astro-ph/0609591
software package e.g. iCosmo. In this case, in order to be-
AmaraA.,RefregierA.,2007,MNRAS,381,1018
comeintegratedintothepackageboththecodeandthesci- BartelmannM.,SchniederP.,2001,Phys.Rept.,340,291,472
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tency MNRAS,365,255,264
Bridle,B.,etal.,2008,arXiv0802.1214
– Thirdlythecodecanbepublishedandturneditintoawebin-
Chevallier,M.;Polarski,D.;2001,IJMPD,10,213
terface,thiscouldbeasanextensionofanexistinginterface
DESCollaboration;2005,eprintarXiv:astro-ph/0510346
(e.g. http://www.icosmo.org) or as a stand alone inter- EisenstienD.,HuW.,1997,ApJ.,511,5
face. HeavensA.,2003,MNRAS,343,1327
HeavensA.,KitchingT.,TaylorA.,2006,MNRAS,373,105,120
TheiCosmosourcecodeitself(Refregieretal.,2008)isan HutP.,2007,Prog.Theor.Phys.Suppl.164,38-53
exampleofthethirdtier,bothopensourceandwebinteractivity. HutererD.&TurnerM.,2001,Phys.Rev.,64,123527
Kitchingetal.(2008)(acosmologicalsystematicsinvestigation) HutererD.,etal.,2006,MNRAS,366,101,114
IvezicA.,etal.,2008,eprintarXiv:0805.2366
is an example of the second tier, some source code which has
KaiserK.,2004,SPIE,5489,11
been integrated into an existing software package as an addi- Kitching T. D., Amara A., Abdalla F., Joachimi B., Refregier A., 2008,
tionalmodule. arXiv:0812.1966
iCosmo can be used as a platform for all three tiers. The LewisA.,ChallinorA.,LasenbyA.;2000,ApJ,538,473,476
LewisA.,BridleS.,2002,Phys.Rev.D66,103511
source code is very modular and can easily be extended, and
Linder,E.;2003,Phys.Rev.Lett.,90,091301
because iCosmo is an existing software package new add-on PeacockJ.,DoddsP.,1996,MNRAS,280,19
modulescanbepublishedineachnewrelease.Finallythemeth- RefregierA.,AmaraA.,KitchingT.,RassatA.,2008,submittedtoA&A
odsoutlinedinthisarticleshowhowaniCosmomodulecanbe RefregierA.,etal.,2008b,Proc.ofSPIE2008,Marseille,France
Smail,I.;Ellis,R.S.;Fitchett,M.J.,1994,MNRAS,270,245
turned into an interactive webpage. New interactive webpages
SmithR.E.,etal.,2003,MNRAS,341,1311
couldeitherbeentirelyindependentorcouldbeincorporatedin
TegmarkM.,EisensteinD.,HuW.,1998,arXiv:astro-ph/9804168
themainsite. Tegmark,M.;TaylorA.,HeavensA.;1997,ApJ,440,22
TysonA.;2006,AIPC,870,44
RassatA.,etal.2008,arXiv:0810.0003
4. Conclusion SzalayA.,BrunnerR.,1999,FGST,16,63
SNAPCollaboration,2005,eprintarXiv:astro-ph/0507460
Cosmologyhadmadegooduseoftheinternetsofaraseithera WrightN.,2006,PASP,118,1711
publicrepositoryforarticlesandcode,orasalarge-scalecompu- Zaldarriaga,M.;Seljak,U.,2000,ApJS,129,431
tationalfarm.Howevertheinteractivepotentialoftheweb,that
canallowcosmologiststoperformcomplexcalculationsonline,
hasthusfarbeenlargelyoverlooked. AppendixA: UserGuideforhttp://www.icosmo.org
We envisage a move towards cloud cosmology in which
InthisAppendixwedescribetheinteractivefeaturesofiCosmo,
computationallydemandingandcomplexprocessescanbeper-
the products available from the website and how to access the
formednon-locally.
mainfeaturesofthewebinterface.
In this article we have outlined the some simple processes
thatwehavelearntinthecreationofanonline,interactive,low-
redshift(darkUniverse)cosmologycalculator.Wehaveoutlined
A.1.BeginningCalculations
howa simple webpage is created,and hosted,andshownhow
cosmological code can be turned into an interactive web site. TheiCosmointeractivewebsiteallowsyoutocalculatecosmo-
Throughout we have used the example of the interactive web logical functions, cosmology observables and Fisher matrices.
site http://www.icosmo.orgwhich is powered by the open These are summarised in Table A.1. We always calculate the
source software iCosmo – for a description of the interactive cosmologyfunctions.Thethreedifferentcalculationscopeswill
featuresonthissiteseeAppendixA. bedescribedinmoredetailinSectionA.6.
Finally we described three levels integration that could be Throughoutallcalculationsweusethefollowingsetofcos-
adoptedbyacosmologistwantingtomaketheircodeeasilyac- mologicalparametersΩ ,Ω ,w ,w ,σ ,Ω ,handthespec-
m DE 0 a 8 B
cessibleonline. tral index n . The curvature density Ω is determined through
s K
8 T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo
Scope Products
CosmologyFunctions Distances,H(z),GrowthFactor
LinearPowerSpectrum,Non-LinearPowerSpectrum
CosmologyObservables LensingPowerSpectrum,BaryonDistanceScales
SupernovaeType-IaMagnitudeDistanceRelation
CosmologyErrors LensingFisherMatrix
BAOFisherMatrix,SupernovaeType-IaFisherMatrix
Table A.1.Therangeofproductsavailableonthewebsite.CosmologyFunctionsarealwayscalculated.Theusercan investigate
theeffectofchangingcosmologicalparametersinthecaseofCosmologyFunctionsandCosmologyObservables.
Step1allowstheusertospecifythecosmology,orcosmolo-
gies(seeSectionA.5)thattheywishtouseinthecalculation.In
thissteptherangeofproductsthatwillbecalculatedisalsocho-
sen, the productsare arrangedinto the three scopes detailed in
TableA.1.Toadvancetothenextstagetheuserclickson“Begin
Calculations”.
Step2willshowsomefurtheroptionsrelevanttotheprod-
ucts chosenin Step 1. The baselineoptionsforthe Cosmology
Functionsare the minimum and maximumredshiftfor the dis-
tance,Hubbleparameterandgrowthfactorcalculations.Forthe
matterpowerspectrumtheminimumandmaximumk-rangeas
wellasthefunctionalformusedinthecalculationscanbecho-
sen. The types of option available are shown in Table A.2. For
Fig.A.1.TheFrontPageoftheiCosmowebsite.TheQuickStart thematterpowerspectrumthelinearformcanbecalculatedus-
Calculatorpanelcanbeseeontherighthandside.Toaccessthe ingeitherEisenstien&Hu(1997)(withorwithoutbaryonoscil-
stepwiseinteractivepagesclickonthe“CosmologyTools”link lations)orBardeenetal.(1986).Thenon-linearpowerspectrum
oronthe“Tools”linkinthenavigationbaracrossthetopofthe canbecalculatedusingeitherPeacock&Dodds(1996)orSmith
page. etal.(2003).
IfeitherCosmologyObservablesorCosmologyErrorswere
choseninStep1thenthechoiceofsurveywillbegiveninStep
2. If “Make Custom” is chosen then the user will be taken to
the choice of Ωm and ΩDE where ΩK = 1 − Ωm − ΩDE at all a furtherStep where thesurveyparametersrelevantto thetype
times. ofproberequiredcanbecustomised.Alternativelyapre-defined
There are two ways in which the interactive part of the surveycan be chosen,the available pre-definedoptionsare de-
iCosmowebsitecanbeaccessed.EitherthoughtheQuickStart tailedinSectionA.4.
panel on the front page or through a step-by-step process that Step3 will appearif “Make Custom” is selected in Step 2.
allowsthe userto customisethe exactscopeand detailsofcal- In Step 3 the user will be shown survey parameters specific to
culationsrequired. thetypeofprobethatisrequired,eitherlensing,baryonacoustic
oscillations (BAO) or type-Ia supernovae. The details of the
optionsavailableforeachoftheprobesare:
A.2.QuickStart
Lensing:
You will find the QuickStart panel on the front page of the
iCosmowebsite, see FigureA.1. To startsimply fill in the val-
– Theareaofthesurveyinsquaredegrees
ues of the cosmological parameters and click on “QuickStart
– Thenumbernoftomographicredshiftbinsusedtoconstruct
Cosmology”.Youwillbetakentoawaitingpagewhilstthecal-
lensingpowerspectra,n(n+1)/2spectrawillbecalculated.
culations are performed. When the calculations are completed
Note that the bin boundaries will be chosen such that the
you will be redirected to the Cosmology Functions interactive
numberofgalaxiesineachbinisapproximatelyconstant
tabdescribedinSectionA.6.
– The surface number density of galaxies in galaxies per
squarearcminutethatcanbeusedforacosmicshearanalysis
– Theintrinsicvarianceinthemeasuredellipticityofgalaxies,
A.3.Step-by-Step
here we use the convention that the variance in measured
TostartyourcalculationandtochooseCosmologyObservables shearisσ =σ /2asexplainedinBartelmann&Schnieder
ǫ γ
andErrorsoptionsfromthebeginningtheusercanbeginastep- (2001)
wisecustomisationofthecalculationsneeded.Thisisreachedby – The uncertainty δ (z) in the redshift of each galaxy, using
z
clickingonanyofthelinksto“Tools”onthefrontpage,Figure the common (1 + z) scaling σ (z) = δ (z)(1 + z). A typ-
z z
A.1, and then clicking on “Interactive Web Tool”. Throughout ical broad band photometric redshift survey should have
the stepwise process the user will only be shown options rel- σ (z)/(1+z) ∼ 0.02to0.05whereasaspectroscopicsurvey
z
evant to the calculations requested, for example if the lensing mayhaveσ (z)/(1+z)<0.001.
z
powerspectrumor lensingFisher matricesare notrequiredthe – The median redshift for the number density distribution of
userwillneverseeanylensing-relatedoptions.Thestructureof galaxies.WeemploythecommonlyusedSmailetal.(1994)
thisflowisoutlinedinFigureA.2. formula
T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo 9
Supernovae:
– Theareaofthesurveyinsquaredegreesthatismultiplyim-
agedtoallowsupernovastudies
– Thesurfacenumberdensityofsupernovaeinsupernovaeper
squarearcminute.Notethatthisdependsonthetotaltimeof
thesurvey,thedepthofthesurvey(magnitudelimit)andthe
intrinsicefficiencyofagalaxyinproducingsupernovae
– The intrinsic variance in supernovae apparent magnitude,
thisistypicallyσ ∼0.15.
m
– The uncertainty δ in the measured apparent magnitude of
m
agivensupernovae,thisvaluewilldependontheparticular
instrumentthatisusedintheobservations.Foraspace-based
instrumentδ ∼0.02andforaground-basedinstrumentthe
m
uncertaintymaybeδ ∼0.05.
m
– The minimumandmaximumredshiftsfor the numberden-
sity ofsupernovae.Note thatforsimplicity we will assume
that the number of supernovae in each redshift bin is con-
stantinredshift.Tocalculatethenumberofredshiftbinswe
set the shotnoise uncertaintyonthe apparentmagnitudein
a givenbintobe1/1000theintrinsicmagnitudedispersion
asistypicallyassumedTegmarketal.(1998)andHuterer&
Turner(2001).
BAO:
– Theareaofthesurveyinsquaredegrees
– The number of redshift bins in which to measure the BAO
scale.Notethatthebinboundarieswillbechosensuchthat
thenumberofgalaxiesineachbinisapproximatelyconstant
– The median redshift for the number density distribution of
galaxies.WeemploythecommonlyusedSmailetal.(1994)
formula
Fig.A.2.Theoutlineofthewebsiteintheformofaflowdiagram
A.4.Surveys highlightingthe inter-relationsbetweenthe optionalinputsand
the resultant outputs. A diamond represents a logical ‘for’ i.e.
BoththeobservablesandtheFishermatrixparametererrorpre-
foroptionAdothisorforoptionBdothat.Atrianglerepresents
dictionsdependon the designof the experiment.The user will
alogical‘if’i.e.ifCischosenthendothis.
findonStep2thatforeachlensingobservableandFishermatrix
requiredwehaveprovidedthechoiceofeitheracustomsurvey
oracurrent/futuresurvey.Thereferencesforthesurveysshown
are:
– DarkEnergySurvey(DES):DESCollab(2005)
– DarkUNiverseExplorer(DUNE):Refregieretal.(2008b)
– Large Synoptic Survey Telescope (LSST): Tyson et al.
(2006),Ivezicetal.(2008)
– Panoramic Survey Telescope & Rapid Response System
(Pan-STARRS1):Kasieretal.(2004)
– SuperNovae Acceleration Probe (SNAP) : SNAP Collab
(2005),Hutereretal.(2005)
The suite of surveys available will continually be updated and
[email protected]
Fig.A.3.Thefirststepinthestepwiseprocessofspecifyingthe
A.5.MultipleCosmologies inputstothecalculation.
InStep1theusercanchoosebetweenoneortwocosmologies.
Thisfeatureistoenablethesensitivityofcosmologicalfunctions
and observablesto certain cosmologicalparameters(or combi- AfterthelastStep(eitherStep2orStep3dependingonthe
nation or parameters) to be investigated.By selecting two cos- productsandlevelofcustomisationneeded)theuseristakento
mologiesfromthedropdownbuttononStep1theusercanfill a waitingpagewhilst thecalculationsare performed.Note that
in the values of each cosmological parameter. On the interac- there are certain ‘illegal’ values of the cosmology parameters
tive pages the user will then see two lines, one for each cos- andcustomisablevariablessuch asΩ < 0 or k > k that
m min max
mology,aboveeitherthecosmologicalfunctionsorobservables the iCosmo source code will not accept. If an illegal value is
beingplotted. passedtotheinteractivecalculatorthewaitingpagewilldisplay
10 T.D.Kitching,A.Amara,A.Rassat,A.Refregier:CloudCosmology:BuildingtheWebInterfaceforiCosmo
Product(s) Options
Distances,HubbleParameter,GrowthFactor z ,z
min max
MatterPowerSpectrum k ,k
min max
Linear:Eisenstien&Hu(1997)(withorwithoutbaryonoscillations)
orBardeenetal.(1986)
Non-Linear:Peacock&Dodds(1996)orSmithetal.(2003)
LensingPowerSpectrumorLensingFisherMatrix ℓ ,ℓ ,Survey
min max
BAODistanceMeasureorBAOFisherMatrix Survey
SupernovaeMagnitude-DistanceorSupernovaeFisherMatrix Survey
TableA.2.TheoptionsgiveninStep2relevantforeachoftheproductschoseninStep1.
amessagedetailingthevaluesthatarediscrepantanddisplaya
buttonwithwhichtheusercanreturntothepreviousstep.After
thecalculationstheuserwillberedirectedtotheInteractivere-
sultspagesdescribedinthenextSectionA.6.
A.6.InteractivePages
InthisSectionwewilldescribetheInteractiveresultswebpages.
When the user arrives at the interactive results page they will
be presented with a number of tabs one can change between
anyofthe tabssimplybyclickingontherelevantheaders.The
CosmologyFunctionstabwillalwaysbepresent,sincetheseare
always calculated, in addition there may also be a Cosmology
ObservablesandaCosmologyErrorstab.Theusercanclickon
anytabandchangebetweentabsinanyorderorcombination.In
additionthenavigationbaratthetopofthepageallowstheuser
tolinktootheriCosmopages.
The options that are given on each tab are shown in Table Fig.A.4. The Interactiveresults tabs in iCosmoweb site. Here
A.3,wherean“&”meansthateachoptioncanbeshownsimul- weshowtheCosmologyFunctionstab,inthisexamplewehave
taneouslyandan“OR”meansthattheoptionsaremutuallyex- chosentwocosmologiesandthedistancesbuttonisshown.
clusive.
The results tabs are all arranged using a common template
whichbeseeninFigureA.4. Thistemplateissplitintoa num-
Below the plot, in each tab, is a “Download Text Output”
berofregions.Thetopregionisdedicatedtotheinputcosmol-
link. By clicking on this link the user can download the data
ogyused,thesurveyparameters(inthe case oftheCosmology
plottedatthepresenttimeinanasciitableformatforlateruse.
Observables and Errors tabs) and the options available for the
Theformatoftheasciifileisshowntotherightofthelinkand
particulartab.
isupdatedsothatitisalwaysrelevanttotheparticularfunction
Associatedwitheachcosmologicalparameterisa boxcon- beingplotted.
tainingthecurrentfiducialvalue.Tochangethefiducialvaluethe To the right of the plot in each tab are the options that are
usercansimplyenteranalternativevalueandclickon“Change relevanttotheparticularproductsthatarebeingplotted,wewill
Cosmology”.Theuserwillthenberedirectedtocalculationpage nowexplaineachtabinturn.
wherethecosmologicalproductswillbere-calculatedusingthe
newcosmology.
A.6.1. CosmologyFunctionsTab
Thecentralpartofeachtab isthegraphicalwindow.When
anyoftheoptionsinatabarechangedtheplotwillbeautomat- The cosmology functions tab presents the calculations of
ically updated.The plotis providedon screen in gif format,to the basic cosmology functions, and will always be present
savetheplotasagifmostbrowsersprovideasaveoptionwhen in the interactive section. To change between the functions
an image is right-clicked.In additionto the gif formatwe pro- the user can click on the relevant button. When the button is
videanencapsulatedpostscriptversionofeveryplot,thiscanbe changedthe“CosmologyOptions”ontherighthandsideofthe
downloadedbyclickingontheplot. graphwillchangetoreflectthenewoptionsavailabletotheuser.
In every tab, to the left of the plot, there are the graphical
optionsthesegivetheusertheabilitytocontrolthexandy-axis Distances When the distances button is selected the angular
ranges of the plot using the “Re-Scale” button. By default the diameter, luminosity, comoving and light travel distances can
autoscalebuttonisselected.Whenautoscaleisselectedtheplot be plotted. Any combination of these distances can be plotted
willbeautomaticallyscaledsuchthatthefunctionplottedwillfit byselectingtherelevantcheckboxes–coloursforeachfunction
withintheviewport.Werecommendthattheautoscalefunction can also be chosen independently using the drop down menu.
isenabledin mostsituations.Inadditiontorescalingthegraph Thesefunctionscanbeplottedasafunctionof:redshiftz,scale
thetypeofaxiscanalsobechanged–fromlineartologarithmic factor1/(1+z)orlook-backtime.
(base10)orviceversa–byclickingontherelevantbuttons.