Groovy, GPars, @CompileStatic and invokedynamic. And Java 8.

Copyright © 2014 Russel Winder 1
Groovy, GPars, @CompileStatic and
invokedynamic. And Java 8.
Russel Winder
email: russel@winder.org.uk
xmpp: russel@winder.org.uk
twitter: @russel_winder
http://www.russel.org.uk

is a programming language.

is a dynamic programming language.

Dynamic language rarely
exhibit high performance.

This is generally not a problem as
most dynamic languages are
usually used in I/O-bound contexts.

In CPU-bound contexts however,
it is a REAL problem.

The biggest issue for Groovy performance
is that floating point values are
BigDecimal by default.

We need an example.



What is the Value of ?
Easy, it's known exactly.
It's .
Obviously.

Putative joke involving Alexander Orlov (*)
and the phrase It's simples. elided as UK“ ”
television-related comedy doesn't travel.
(*) A fairly cute meerkat.

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.

4
=∫0
1 1
1x2
dx

One Possible Algorithm
● Use quadrature to estimate the value of the integral
– which is the area under the curve.
=
4
n
∑i=1
n 1
1
i−0.5
n

2
With n = 3 not much to do,
but potentially lots of error.
Use n = 107
or n = 109
?
Embarrassingly
parallel.

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
fork join
Data parallel

Back to the BigDecimal issue…

…to the code:

As with (almost) all programming language,
Groovy is focussed on sequential activity.

In a multicore world, we harness all the
cores to improve performance.

The Java Platform offers threads,
Java, and hence Groovy, can use them.

Shared memory multithreading is an
infrastructure technique.

java.util.concurrent

Concurrency can be used for
I/O-bound systems, but…

…concurrency can also be used
for CPU-bound systems.
Parallelism.

Parallelism is about performance.

Look at some code…

Dynamism and parallelism are
rarely good bedfellows.

@CompileStatic is about…
…eliding dynamism.
…about performance.

invokedynamic is about…
…supporting dynamism.
…performance.

Java 8
The greatest revolution of
Java since 1994.
A far bigger revolution of
Java than Java 5.

Java 8
Introduces various things, the most
important of which are:
Lambda expressions.
Default methods in interfaces.

Java 8
as a consequence of
lambda expressions introduces:
Streams†
.
†
And parallelism, and parallelism is about performance.

More codes…

Needs You…

Groovy, GPars, @CompileStatic and
invokedynamic. And Java 8
Russel Winder
email: russel@winder.org.uk
xmpp: russel@winder.org.uk
twitter: @russel_winder
http://www.russel.org.uk

Groovy, GPars, @CompileStatic and invokedynamic. And Java 8.

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