DIVA & DIVAnd interpolation tools

All you need to know about them

gher-ulg
@GHER_ULiege
0000-0002-0265-1021

What (who?) is DIVA?

Data
Interpolating
Variational
Analysis

Software tool to interpolate in situ observations

What is [not] DIVAnd?

= n dimensional version of DIVA

≠ not a new release of DIVA,
but a brand new code

What's the goal of DIVA{nd}?

Get gridded field from in situ data

What are the differences
between them?

Mathematical formulation

Programming language

User interface

Who wrote the code?


and a few others since 1991

Why ,
why not or ?


Source: http://daftpunk.wikia.com, No copyright infringement is intended

Better...


Multiple dispatch
Math-friendly syntax
Unicode support: π, η, ∫ϵα 


julia> 🌊 = 1./3.
julia> cos(🌊*π)
0.5000000000000001

Faster

Just-in-time (JIT) compiled
Parallelism 


function fib(n::Int)
f=Vector{Int}(undef, n+1)
f[1]=f[2]=1;
for i=3:n+1
f[i]=f[i-1]+f[i-2]
end
return f
end
ff = @time fib(400000000);
1.158971 seconds (18.52 k allocations: 2.981 GiB, 0.84% gc time)

Stronger

Metaprogramming:
Julia programs can read, analyse, generate other Julia programs

"Easy" interfacing: R, Python, ... 


@pyimport numpy.random as nr
nr.rand(3,4)

Harder

Learning a new and evolving language
Transition from 0.6 to 1.0


How can I get the code?


https://github.com/gher-ulg/DIVA
https://github.com/gher-ulg/DIVAnd.jl

Who's using it?

SeaDataCloud regional leaders, creating climatologies

https://www.seadatanet.org/Products/Climatologies

EMODnet Chemistry regional leaders

http://www.emodnet-chemistry.eu/products

EMODnet Biology (specific products)

http://www.emodnet-biology.eu/data-products

Example: zooplankton count in the Baltic Sea

BioOracle: http://www.bio-oracle.org/index.php

Can I test it without installing it?

DIVA (2D) within Ocean Data View

http://odv.awi.de/

DIVA-on-Web (2D)

http://ec.oceanbrowser.net/emodnet/diva.html

Jupyter notebooks inside the Virtual Research Environment

DIVAnd REST API (2D)

Why (do we think) it is better than any other method?

Fast, robust, specific to ocean
Separation of sub-domains
Associated error field

Can I interpolate velocity measurements?

## High-frequency radar interpolation Synthetic velocity field, red arrow = measurement ![synthetic:](images/current1.png)
## High-frequency radar interpolation Adding the influence of the coast ![Coastline:](images/current2.png)
## High-frequency radar interpolation Low horizontal divergence of currents ![Divergence:](images/current3.png)
## High-frequency radar interpolation Including Coriolis force and geostrophically balanced mean flow
![Coriolis:](images/divand_hfradar_3D_Coriolis_geo.png) Test areas: Ibiza Channel, Gulf of Trieste

Would you help me use it?

Why may I not be able to use it?

Hofstadter's Law:
It always takes longer than you expect,
even when you take into account Hofstadter's Law.

How to cite?

Barth, A., Beckers, J.-M., Troupin, C., Alvera-Azcárate, A., and Vandenbulcke, L.: DIVAnd-1.0: n-dimensional variational data analysis for ocean observations, Geosci. Model Dev., 7, 225-241, doi:10.5194/gmd-7-225-2014, 2014.

One DOI per code release

2.3.1 →
2.3.0 →
...

Who is Julia?

Julia Child (1912-2004)

By Lynn Gilbert - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=51678880

Thanks for your attention