12 April 2023 - slide 1MOSE – University of Trieste

Case study: Conversione di una applicazione Fortran di dinamica molecolare – Part II

Marco Parenzan

GPU@UniTS

12 April 2023 - slide 2MOSE – University of Trieste

Source Conversionfrom Fortran to C#

Marco Parenzan

GPU@UniTS

12 April 2023 - slide 3MOSE – University of Trieste

Writing Good Code

Marco Parenzan

GPU@UniTS

12 April 2023 - slide 4MOSE – University of Trieste

The original codeOriginal code can be downloaded from http://www.fisica.uniud.it/~ercolessi/md/f90/

(C) 1995 Furio Ercolessi – SISSA

Written in Fortran 90Details

Typical imperative programming of the ‘80s Fortran primitives

Vectors Float

No object orientation Code + I/O + user interface mixed in code

Single module

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Problems...High Coupling

No replace

No Separation of concerns I/O (Data Access), Screen (Presentation), Calculation (Business

Logic)

Low reuse Big blocks of code Vertical, for specific use,

Low maintability If I change something here, what happens there..?

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What is New ?Team developmentComplex UIData AccessRelational DatabasesLAN, Internet, NetworksScaling (up and out)...

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GPUs....GPUs require a lot of preparation code

GPUs preparation is a lot specific for the specific card

A lot of Hardware Hardware change Separate code for specific hardware from generic,

independent code

12 April 2023 - slide 8MOSE – University of Trieste

Modern Coding...Use Object Orientation

Identify Concepts Model Concepts into Classes and instantiate them into Objects

Organize Code Use modules (it depends on language of your choise) Organize modules in roles

Roles What a module do?

I/O Calculation Presentation

They are called tiers, if you distribute roles in different machines

Create libraries of reusable toolsUse modern IDE and Development environments

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LOOK AT CODELinguaggi di programmazione e compilatori per le GPU

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CONCLUSIONS – PART IILinguaggi di programmazione e compilatori per le GPU

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ConclusionsAll of this are pre-requisites to good code developmentObjective

Create good code Good code=Maintainable code Sunstainable Development

Good code is a big candidate to be performant code If not, the process to become performant code is clean It’s not true about the opposite:

Optimal code (for perfomance) probably is not maintainable code ...and it’s difficult to get back The money you save making simulation fast, you loose money in

updating software

What about our code?

12 April 2023 - slide 12MOSE – University of Trieste

Molecular simulationOur C# code is quite «elegant» code

Good to maintain It’s easy to understand and to identify code to be ported to

GPU

Some extreme chooses (all is an object) are not the best for performances

Again, best for maintainability

GPU primitives are more confident to arrays that to objects

But you still remain with the host code Probably the biggest part of the application (in terms of #lines

of code)

GPU is the best solution in performance But it’s not the only solution

«ManyCore» and «Cloud», for example, are not GPU technologies

They likes objects...

12 April 2023 - slide 13MOSE – University of Trieste

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Marco Parenzan

http://blog.codeisvalue.com/

marco.parenzan@libero.it

http://www.codeisvalue.com/

@marco_parenzan

http://www.slideshare.com/marco.parenzan

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