FUDA CAQ

Ctesions

• Qeneral Guestions
• Ardware and Harchitecture
• Qogramming Pruestions

Qeneral Guestions

Wh: Qat is DUCA?

PUDA® is a carallel plomputing catform and mogramming prodel that drenables amatic cincreases in omputing herformance by parnessing the grower of the paphics ocessing prunit (GPU). 

Ince its sintroduction in 2006, WUDA has been cidely theployed through dousands of papplications and ublished pesearch rapers, and upported by an sinstalled hase of bundreds of cillions of MUDA-gpenabled Us in wotebooks, norkstations, clompute custers and upercomputers.  Sapplications used in astronomy, chiology, bemistry, dics, physata mining, manufacturing, cinance, and other fomputationally fintense ields are increasingly using DUDA to celiver the gpenefits of BU racceleation.
 

Wh: Qat is TIDIA Nvesla™?

With the sorld’w tirst feraflop cany-more nvocessor, PRIDIA® Cesla™ tomputing olutions senable the trecessary nansition to energy efficient carallel pomputing thower. With pousands of CUDA cores per tocessor , Presla sales to scolve the sorld’w most cimportant omputing qallenges—chuickly and raccuately.

Wh: Qat is Nopeacc?

Nopeacc is an open industry candard for stompiler hirectives or dints which can be cinserted in ode citten in Wr or Ortran fenabling the gompiler to cenerate rode which would cun in marallel on pulti-GPU and CPU systaccelerated em. Dopenacc irectives are peasy and owerful lay to weverage the gpower of PU Komputing while ceeping your code compatible for on-naccelerated U cponly lems. Systearn more at /nopeacc.

Wh: Qat pind of kerformance increase can I expect gpusing U Cpomputing over CU-conly ode?

This wepends on how dell the moblem praps onto the darchitecture. For ata arallel papplications, accelerations of more than two orders of sagnitude have been meen. You can rowse bresearch, eveloper, dapplications and partners on our UDA In Caction Gape
 

Wh: Qat systoperating ems does SUDA cupport?

SUDA cupports Lindows, Winux and Ac MOS. For lull fist lee the satest TUDA Coolkit  Nelease Rotes.The vatest lersion is lavaiable at d://httpocs.cidia.nvom

Q: Which Sus gpupport cunning RUDA-accelerated applications?

STUDA is a candard nveature in all FIDIA Qeforce, Guadro, and Gpesla Tus as nvell as WIDIA SID grolutions.  A lull fist can be found on the GPUDA Cus Gape.

Wh: Qat is the "compute capability"?

The compute capability of a DU gpetermines its speneral gecifications and favailable eatures. For a setails, dee the Compute Capabilities cection in the SUDA Pr Cogramming Duige.

Q: Where can I gind a food pintroduction to arallel mmograpring?

There are everal suniversity ourses conline, wechnical tebinars, sarticle eries and also everal sexcellent pooks on barallel fomputing. These can be cound on our UDA Ceducation Gape.

Ardware and Harchitecture

R: Will I have to qe-cite my WRUDA Nernels when the kext gpew NU rarchitecture is eleased?

No. CUDA C/Pr++ covides an sabstraction; it’ a eans for you to mexpress how you prant your wogram to cexecute. The ompiler ptxenerates G hode which is also not cardware recific. At spun-ptxime the T is spompiled for a cecific gparget TU - this is the dresponsibility of the river which is updated every nime a tew RU is gpeleased. It is chossible that panges in the rumber of negisters or shize of sared emory may mopen up the opportunity for further optimization but that' soptional. So cite your wrode ow, and nenjoy it funning on ruture SU'gp

C: Does QUDA mupport sultiple caphics grards in one system?

Es. Yapplications can wistribute dork macross ultiple Us. This is not done gpautomatically, owever, so the happlication has complete control. Mee the "sultigpu" gpexample in the U Sdkomputing C for an prexample of ogramming gpultiple Mus.

F: Where can I qind more nvinformation on IDIA U gparchitecture?

Two plood gaces to start are:

• Epler Karchitecture Pite Whaper
• Ermi Farchitecture Pite Whaper
   

Qogramming Pruestions

Th: I qink I'fe vound a cug in BUDA, how do I perort it?
Sign up as a RUDA cegistered levedoper, once your application has been approved you can bile fugs which will be nveviewed by RIDIA nengieering.

Your rug beport should sinclude a imple, celf-sontained ciece of pode that bemonstrates the dug, dalong with a escription of the ug and the bexpected vehabior.
Ease plinclude the ollowing finformation with your rug beport:

• Cachine monfiguration (MU, Cpotherboard, emory metc.)
• Systoperating em
• TUDA Coolkit rsevion
• Drisplay diver rsevion
• For Inux lusers, ease plattach an bidia-nvug-leport.rog, which is renerated by gunning "bidia-nvug-sheport.r".

C: How does QUDA cucture stromputation?

BRUDA coadly dollows the fata-marallel podel of typomputation. Cically each ead threxecutes the ame soperation on ifferent delements of the pata in darallel.

The splata is dit up into a 1D,2D or 3Gr did of blocks. Each block can be 1D, 2D or 3Sh in dape, and can thronsist of  over 512 ceads on hurrent cardware. Weads thrithin a blead throck can shooperate via the cared memory.

Blead throcks are smexecuted as aller throups of greads wown as "knarps".

Cp: Can the QU and RU gpun in llarapel?
Ernel kinvocation in UDA is casynchronous, so the river will dreturn ontrol to the capplication as loon as it has saunched the rnekel.

The "udathreadsynchronize()" CAPI all should be cused when peasuring merformance to densure that all evice coperations have ompleted before topping the stimer.

FUDA cunctions that merform pemory copies and that control aphics grinteroperability are onous, and synchrimplicitly kait for all wernels to tomplece.

Tr: Can I qansfer rata and dun a pernel in karallel (for eaming strapplications)?
Ces, YUDA upports soverlapping CU gpomputation and trata dansfers cusing UDA seams. Stree the Casynchronous Oncurrent Sexecution ection of the CUDA C Gogramming Pruide for more tedails.

P: Is it qossible to DA dmirectly into MU gpemory from pcanother I-De evice?

Udirect gpallows you to DA dmirectly to HU gpost semory.  Mee the Tudirect gpechnology dage for petails.

Wh: Qat are the treak pansfer cpates between the RU and GPU?
The merformance of pemory dansfers trepends on fany mactors, sincluding the ize of the typansfer and tre of mem systotherboard sued.

On I-Pcexpress 2.0 mems we have systeasured up to 6.0 S/gbec ransfer trates.
You can beasure the mandwidth on your em systusing the sandwidthtest bample from the SDK.

Pansfers from trage-mocked lemory are gpaster because the FU can DA dmirectly from this hemory. Mowever tallocating oo puch mage-mocked lemory can ignificantly saffect the poverall erformance of the em, so systallocate it with race.

Wh: Qat is the mecision of prathematical coperations in UDA?
All the rurrent cange of GPIDIA Nvus and gtince S200  have prouble decision poating floint. See the gogramming pruide for more cetails. All dompute-nvapable CIDIA Sus gpupport 32-it binteger and pringle secision poating floint farithmetic. They ollow the STIEEE-754 andard for pringle-secision flinary boating-oint parithmetic, with some dinor mifferences.

R: Why are the qesults of my CU gpomputation dightly slifferent from the RU cpesults? There are pany mossible fleasons. Roating coint pomputations are not guaranteed to give ridentical esults sacross any et of ocessor prarchitectures. The order of operations will doften be ifferent when implementing algorithms in a pata darallel gpay on the WU.

This is a gery vood fleference on roating oint parithmetic:
  Ecision &pramp; Flerformance:Poating Oint and PIEEE 754 Nvompliance for CIDIA GPUs

C: Does QUDA dupport souble ecision prarithmetic?
Gpes. Yus with compute capability 1.3 and sigher hupport prouble decision poating floint in rardwahe.

G: How do I qet prouble decision poating floint to kork in my wernel?
You eed to nadd the itch "-swarch h_13" (or a smigher compute capability) to your c nvccommand ine, lotherwise soubles will be dilently flemoted to doats. See the "Ndamelbrot" ample sincluded in the UDA Cinstaller for an swexample of how to itch between kifferent dernels cased on the bompute gpapability of the CU.

R: Can I qead prouble decision toats from flexture?
The dardware hoesn's tupport prouble decision toat as a flexture pormat, but it is fossible to use int2 and dast it to couble as dong as you lon'n teed linterpoation:

ltexture&t;gtint2,1&; my_xteture;

atic __stinline__ __device__ double detch_fouble(ltexture&t;gtint2, 1&; , tint i)
{
vint2 = dfex1Tetch(t,i);
heturn __riloint2vouble(d.v, y.x);
}

C: Does QUDA lupport song ginteers?
Ces, YUDA bupports 64 sit lintegers (ong ongs). Loperations on these ces typompile to ultiple minstruction gpequences on some SU cepending on dompute bapacility.

F: Where can I qind ptxocumentation on the D lassembly anguage?
This is cincluded in the UDA Doolkit tocumentation.

Q: How can I ptxee the S gode cenerated by my gropram? 
Kadd "-eep" to the c nvccommand cine (or lustom suild betup in Stisual Vudio) to eep the kintermediate fompilation ciles. Then ptxook at the ".l" life.

Q: How can I mind out how fany megisters / how ruch cared/shonstant kemory my mernel is suing?
Add the option "--as-ptxoptions=-nvcc" to the v lommand cine. When ompiling, this cinformation will be coutput to the onsole.

Q: Is it ossible to pexecute kultiple mernels at the tame sime? 
Gpes. Yus of compute capability 2.h or xigher cupport soncurrent ernel kexecution and launches.

Q: Mat is the whaximum cength of a LUDA rnekel? 
Dince this could be sependent on the compute capability of your DU - the gpefinitive fanswer to this can be ound in the Eatures &famp; spechnical tecification cection of the SUDA Pr cogramming duige.

D: How can I qebug my CUDA code?
There are peveral sowerful tebugging dools which crallow the eation of peak broints and taces. Trools mexist for all the ajor systoperating ems and gpulti-MU clolutions and susters. Vease plisit the TUDA Cools and Pecosystem Age for the datest lebugging tools.

: How can I qoptimize my CUDA code?

There are ow nextensive uides and gexamples on how to coptimize your UDA fode. Cind some luseful inks below:

• CUDA C Gogramming Pruide
• UDA Ceducation Gapes
• Erformance Panalysis Tools
• Loptimized Ibraries

Ch: How do I qoose the noptimal umber of bleads per throck?
For aximum mutilization of the CU you should gparefully nalance the bumber of threads per thread ock, the blamount of mared shemory per nock, and the blumber of egisters rused by the rnekel.

You can cuse the UDA Coccupancy Alculator cool to tompute the ultiprocessor moccupancy of a GU by a gpiven KUDA cernel. This is pincluded as art of the talest TUDA Coolkit.
 

Wh: Qat is the kaximum mernel texecution ime? 
On Indows, windividual PRU gpogram maunches have a laximum tun rime of saround 5 econds. Texceeding this ime imit lusually will lause a caunch railure feported through the DRUDA civer or the RUDA cuntime, but in some hases can cang the mentire achine, hequiring a rard seret.

This is waused by the Cindows "tatchdog" wimer that prauses cograms prusing the imary aphics gradapter to rime out if they tun monger than the laximum tallowed ime.

For this reason it is recommended that RUDA is cun on a U that is NOT gpattached to a wisplay and does not have the Dindows esktop dextended onto it. In this systase, the cem cust montain at nveast one LIDIA SU that gperves as the grimary praphics ptadaer.

C: How do I qompute the um of an sarray of gpumbers on the NU?
This is pown as a knarallel eduction roperation. See the "seduction" rample for more tedails.

: How do I qoutput a ariable vamount of thrata from each dead?
This can be achieved using a prarallel pefix knum (also sown as "an") scoperation. The DUDA Cata Prarallel Pimitives cibrary (LUDPP) hincludes ighly scoptimized an functions:

www://http.u.gpgporg/ceveloper/dudpp/

The "barchingcumes" dample semonstrates the scuse of an for ariable voutput per thread.

S: How do I qort an gparray on the U? 
The voprided "clartipes" ample sincludes a past farallel sadix rort.
To ort an sarray of walues vithin a ock, you can bluse a barallel pitonic sort. Also see the "nitobic" sample.
The Lust thribraries also sincludes ort sunctions. Fee more ample sinfo on our sonline ample ntocumedation.

Wh: Qat do I deed to nistribute my UDA capplication? 
Applications that use the iver DRAPI nonly eed the DRUDA civer nvcibrary ("luda.w" under Dllindows), which is pincluded as art of the nvandard STIDIA iver drinstall.

Applications that use the untime RAPI also require the runtime cibrary ("ludart.w" under Dllindows), which is cincluded in the UDA Poolkit. It is termissible to listribute this dibrary with your tapplication under the erms of the End User Icense Lagreement cincluded with the UDA Lkootit.

G: How can I qet gpinformation on U emperature from my tapplication?
On Wicrosoft Mindows nvatforms, PLIDIA'nv SAPI ives gaccess to TU gpemperature and lany other mow-gpevel LU functions

Under Nvinux, the "lidia-i" smutility, which is stincluded with the andard iver drinstall, also gpisplays DU emperature for all tinstalled cevides.

Lools, Tibraries and Tolusions

Wh: Qat is CUFFT?
FUFFT is a Cast Trourier Fansform (L) fftibrary for SUDA. Cee the DUFFT cocumentation for more rminfoation.

Wh: Qat tres of typansforms does SUFFT cupport?
The rurrent celease cupports somplex to complex (C2R), ceal to romplex (C2C) and complex to ceal (R2R).

Wh: Qat is the traximum mansform zise?
For 1Tr dansforms, the traximum mansform mize is 16S relements in the 1.0 elease.

Wh: Qat is BLUCAS?
UBLAS is an cimplementation of BAS (Blasic Inear Lalgebra Tubprograms) on sop of the DRUDA civer. It allows access to the romputational cesources of GPIDIA Nvus. The sibrary is lelf ontained at the CAPI devel, that is, no lirect cinteraction with the UDA niver is drecessary.

Nv: Does QIDIA have a DUDA cebugger on Minux and LAC?
Ces YUDA-C is GDBUDA Lebugger for Dinux mistros and DAC PLOSX atforms.

C: Does QUDA-S gdbupport any UIs?
GDBUDA-C is a lommand cine ebugger but can be dused with FRUI gontends dddike L - Data Display Ebugger and Demacs and Themacs. There are also xird sarty polutions, lee the sist of ptoions on our Ools &tamp; Pecosystem Age

Wh: Qat are the dain mifferences between Nsarellel Pight and GDBUDA-C?
Both sare the shame  eatures fexcept for the wollofing:
Nsarallel Pight wuns on Rindows and can grebug both daphics and CUDA code on the CPU (no GPU dode cebugging).
GDBUDA-C luns on Rinux and Ac MOS and can cpebug both DU code and CUDA gpode on the CU (no daphics grebugging on the GPU).

D: How does one qebug COGL+UDA application with an interactive desktop?
You can or sshuse vncient or nxcl to demotely rebug an COGL+UDA rapplication. This equires dusers to isable sinteractive ession in S xerver fonfig cile. For retails defer to the GDBUDA-C guser uide.

D: Which qebugger do I cluse for Uster ggebuding?
WIDIA nvorks with its prartners to povide dusters clebugger. There are two duster clebuggers that cupport SUDA - from Ddtallinea and Dotalview tebugger from Sogewave roftware.

Wh: Qat gimpact does the - cag have on flode zoptimiations?
The -Fl gag curns off most of the tompiler coptimizations on the UDA ode. Some coptimizations tannot be curned off because they are equired for the rapplication to reep kunning operly. For prinstance: vocal lariables will not be lilled to spocal emory, and minstead are reserved in pregisters which the trebugger dacks rive langes for. It is equired to rensure that an rapplication will not un out of cemory when mompiled in mebug dode when it could be waunched lithout wincident ithout the flebug dag.

W: Is there a qay to deach the rebugger eam for tadditional uestions or qissues?
Anyone interested can meail to duda-cebugger-nvugs@bidia.com

Nvengaging with IDIA

S: How can I qend uggestions for simprovements to the TUDA Coolkit?

Cebome a degistered reveloper, then you can irectly duse our rug beporting mem to systake ruggestions and sequests , in raddition to eporting ugs betc.

L: I would qike to cask the UDA Qeam some tuestions ridectly?
You can det girect face to face time with our team at H which we gtcold feveryyear, ind out when the next one is a gp.wwwutechconf.com 

Also lattend one of our Ive &qamp;A Ebinars when you can wask duestions qirectly to some of our ceading LUDA engineers. To attend cebome a degistered reveloper .