intro update

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2021-01-26 13:04:57 +08:00
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@@ -10,34 +10,46 @@ active, quickly growing and exciting field of research -- we want to provide
a starting point for new researchers as well as a hands-on introduction into
state-of-the-art resarch topics.
```{figure} resources/overview-pano.jpg
---
height: 240px
name: overview-pano
---
Understanding our environment, and predicting how it will evolve is one of the key challenges of humankind.
```
## Motivation
From weather forecasts (? ) over X, Y,
... more ...
to quantum physics (? ),
From weather and climate forecasts {cite}`stocker2014climate`,
over quantum physics {cite}`o2016scalable`,
to the control of plasma fusion {cite}`maingi2019fesreport`,
using numerical analysis to obtain solutions for physical models has
become an integral part of science.
At the same time, machine learning technologies and deep neural networks in particular,
have led to impressive achievements in a variety of field.
Among others, GPT-3
has recently demonstrated that learning methods can
achieve astounding accuracy for processing natural language.
Also: AlphaGO, closer to physics: protein folding...
This is a vibrant, quickly developing field with vast possibilities.
have led to impressive achievements in a variety of fields:
from image classification {cite}`krizhevsky2012` over
natural language processing {cite}`radford2019language`,
and more recently also for protein folding {cite}`alquraishi2019alphafold`.
The field is very vibrant, and quickly developing, with the promise of vast possibilities.
The successes of DL approaches have given rise to concerns that this technology has
At the same time, the successes of deep learning (DL) approaches
has given rise to concerns that this technology has
the potential to replace the traditional, simulation-driven approach to
science. Instead of relying on models that are carefully crafted
from first principles, can data collections of sufficient size
be processed to provide the correct answers instead?
In short: this concern is unfounded. As we'll show in the next chapters,
it is crucial to bring together both worlds: _classical numerical techniques_
and _deep learning_.
Very clear advantages of data-driven approaches would lead
to a "yes" here ... but that's not where we stand as of this writing.
Given the current state of the art, these clear breakthroughs
are outstanding, the proposed techniques are novel,
One central reason for the importance of this combination is
that DL approaches are simply not powerful enough by themselves.
Given the current state of the art, the clear breakthroughs of DL
in physical applications are outstanding, the proposed techniques are novel,
sometimes difficult to apply, and
significant difficulties combing physics and DL persist.
significant practical difficulties combing physics and DL persist.
Also, many fundamental theoretical questions remain unaddressed, most importantly
regarding data efficienty and generalization.
@@ -47,22 +59,23 @@ been developed to solve fundamental model equations such
as the Navier-Stokes, Maxwells, or Schroedingers equations.
Seemingly trivial changes to the discretization can determine
whether key phenomena are visible in the solutions or not.
Rather than discarding the powerful methods that have been
carefully developed in the field of numerical mathematics, it
is highly beneficial for DL to use them as much as possible.
```{admonition} Goal of this document
```{admonition} Goals of this document
:class: tip
Thus, a key aspect that we want to address in the following in the following is:
Thus, the key aspects that we want to address in the following are:
- explain how to use DL,
- how to combine it with existing knowledge of physics and simulations,
- **without throwing away** all existing numerical knowledge and techniques!
- and how to combine it with existing knowledge of physics and simulations,
- **without throwing away** all existing numerical knowledge and techniques.
```
Rather, we want to build on all the neat techniques that we have
at our disposal, and use them as
much as possible. I.e., our goal is to _reconcile_ the data-centered
Thus, we want to build on all the powerful techniques that we have
at our disposal, and use them wherever we can.
I.e., our goal is to _reconcile_ the data-centered
viewpoint and the physical simuation viewpoint.
Also interesting: from a math standpoint ...
''just'' non-linear optimization ...
## Categorization
@@ -124,8 +137,9 @@ each of the different techniques is particularly useful.
A brief look at our _Notation_ won't hurt in both cases, though!
```
---
## A brief history of PBDL in the context of Fluids
<!-- ## A brief history of PBDL in the context of Fluids
First:
@@ -135,7 +149,7 @@ Chu, descriptors, early but not used
Ling et al. isotropic turb, small FC, unused?
PINNs ... and more ...
PINNs ... and more ... -->
## Deep Learning and Neural Networks
@@ -160,4 +174,5 @@ we only deal with _regression_ problems in the following.
maximum likelihood estimation
Also interesting: from a math standpoint ''just'' non-linear optimization ...