Why Go is an important programming language

Why Go is an
Important Language

Prof Russel Winder
email: russel@winder.org.uk
xmpp: russel@winder.org.uk
twitter: russel_winder

Copyright © 2013 Russel Winder 1

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controversial
adjective
of, pertaining to, or characteristic of controversy;
polemical


controversy
noun
dispute, argument, or debate, especially one
concerning a matter about which there is
strong disagreement


polemic
noun
a strong verbal or written attack on
someone or something


Go, made public late 2009.


It's a better C.


Strong, static type checking.


Garbage collected.


Statically linked.


Aware of DVCS repositories.


No classes.


Separation of state and behaviour.


Focus on modern, multicore hardware.


Concurrency is a tool for structuring execution where a
single processor is used by multiple computations.

Parallelism is about making a computation complete
faster than using a single processor.


Parallelism is performance improvement.

Performance improvement requires parallelism.


People should tremble in fear

at the prospect of using

mutable
shared-memory
multithreading.

Locks deny parallelism.

The whole purpose of a lock is to
prevent parallelism.


Locks are needed only if
there is mutable shared state.


Avoid mutable shared state.


Use processes and message passing.


It's all easier if processes
are single threaded.


Applications and tools programmers
need computational models with
integrated synchronization.


Actors Dataflow
Independent processes Operators connected by
communicating via channels with activity
asynchronous exchange triggered by arrival of
of messages data on the channels.

CSP Data Parallelism
Sequential processes
Transform a sequence to
connected by channels
another sequence where all
using synchronous message
individual actions happen
exchange (rendezvous).
at the same time.


Data Parallelism
at the same time.


Actors
Independent processes
communicating via
asynchronous exchange
of messages


Dataflow
Operators connected by
channels with activity
triggered by arrival of
data on the channels.


CSP


Actors Dataflow
Independent processes Operators connected by
communicating via channels with activity
asynchronous exchange triggered by arrival of
of messages data on the channels.

CSP Data Parallelism
at the same time.


Agents
A wrapper for some
Active Objects shared mutable state.
An object that is actually
an actor but looks like a
full service object.
Fork/Join
An toolkit for tree structured
concurrency and parallelism.

Software Transactional Memory
Wrappers for mutable values that uses transactions
rather than locks.

Example.




What is the Value of ?

Easy, it's known exactly.

It's .

Obviously.


It's simples
Александр Орлов 2009


Approximating 
● What is it's value represented as a floating point
number?
● We can only obtain an approximation.
● A plethora of possible algorithms to choose from, a
popular one is to employ the following integral
equation.

 1 1
=∫0 dx
4 1x 2


One Possible Algorithm
● Use quadrature to estimate the value of the integral
– which is the area under the curve.
4 n 1
= ∑i=1
n i−0.5 2
Embarrassingly 1 
parallel. n

With n = 3 not much to do,
but potentially lots of error.
Use n = 107 or n = 109?


Because addition is commutative and
associative, expression can be
decomposed into sums of partial sums.


a+b+c+d+e+f

=

(a+b)+(c+d)+(e+f)


Scatter – Gather

map reduce

Code!


If you want the code, clone the Git repository:

http://www.russel.org.uk/Git/Pi_Quadrature.git


Or if you just want to browse:

http://www.russel.org.uk/gitweb


Multicore and multiprocessor are now
the norm, not the exception.


Parallelism only matters if
computational performance matters.


Unstructured synchronization
of concurrent systems
is not a feasible approach.


Actors, CSP, Dataflow, and
Data parallelism
are the future of
applications structure.


Passing messages between
processes is the way forward.


Shared memory concurrency
is a dead end for applications.


Goroutines

and

channels


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Why Go is an
Important Language

Prof Russel Winder
email: russel@winder.org.uk
xmpp: russel@winder.org.uk
twitter: russel_winder


Why Go is an important programming language

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