The free lunch is over

The Free Lunch Is Over

The Free Lunch Is OverA Fundamental Turn Toward Concurrency in Software

(By Herb Sutter)

Presenter

Muhammad Rizwan

Sr. Software Engineer

muhammad.rizwan@techlogix.xom

+92 51 111 859 859 Ext 108

Agenda

• Moore's Law

• Amdahl's law

• Performance Factors

• Free Lunch

• Power Wall

• Free Lunch is Over

• Conclusion

• Future

• References

Moors Law

Moor’s Law

• Over the history of computing hardware,

the number of transistors on integrated

circuits doubles approximately every two

years Transistor

Count

If the current trend continues

to 2020, the number of

transistors would reach 32

billion.

Amdahl's law

Amdahl's law

The speedup of a

program using

multiple processors

in parallel

computing is limited

by the sequential

fraction of the

program. For example, if 95% of the program can

be parallelized, the theoretical maximum

speedup using parallel computing would

be 20× as shown in the diagram, no

matter how many processors are used

Performance Factors

Performance Factors

Clock Speed

Execution Optimization

Cache

Free Lunch

What Free Lunch Is Actually?

Free Lunch

Programmers haven't really had to worry much about performance or concurrency because of Moore's Law

The traditional approach to application performance was to simply wait for the next generation of processor; most software developers did not need to invest in performance tuning, and enjoyed a “free lunch” from hardware improvements.

Why we did not see 4GHz

processors in Market?

Power Wall

Power Wall

Power Wall

Power Wall

This Free Lunch is Over

Right Now…

Free Lunch is Over

Your free lunch will soon be over. What can you do about it?

What are you doing about it?

The major processor manufacturers and

architectures, from Intel and AMD to Sparc and

PowerPC, have run out of room with most of their

traditional approaches to boosting CPU performance.

Instead of driving clock speeds and straight-line

instruction throughput ever higher, they are instead

turning toward hyper threading and multicore

architectures

Chip designers are under so much pressure to

deliver ever-faster CPUs that they’ll risk changing

the meaning of your program, and possibly break

it, in order to make it run faster

Conclusion

The free lunch is over

Performance Free Lunch

Moore’s law has changed

Futurists such as Ray Kurzweil, Bruce Sterling, and Vernor Vinge believe that the

exponential improvement described by Moore's law will ultimately lead to a technological

singularity: a period where progress in technology occurs almost instantly.

Amdahl’s law demands shift in software

concepts

Factors Hyper threading

Multicore

Cache

Future

Now ball is in programmers

court

-> With multicore processors, programs written in sequential mode will no longer

surf on the wave of this generation processors.

-> To surf in new wave, programs need to be well written parallel.

-> Programming language and system will increasingly be forced to deal well

with concurrency.

-> Concurrency is the next major revolution in how we write software.

-> Applications will increasingly need to be concurrent if they want to fully exploit

continuing exponential CPU throughput gains.

-> Efficiency and performance optimization will get more, not less, important.

New Law

Only Parallel Applications

Will Survive

References

References

The Free Lunch Is Over By Herb Sutter

A Fundamental Turn Toward Concurrency in Software

The Free Lunch Is Over By Ricardo Hermann , Thadeo Carmo

Developing Concurrent Software

Is the free lunch really over? Scalability in Many-core Systems By Michael Wrinn

The Price of Free LunchProgramming in Multicore Era

Any Question?