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Introduction

Questions

  • What is the Purpose of Formalism in Computer Science?

  • What is software development life cycle

  • There seem to be many concepts in this course. What do they mean?

Content

We start with a more theoretical introduction covering the software and tools and mindsets for software development.

Learning objectives of 'SDLC tools'

  • Identify the main topics and objectives for the week's lessons.
  • Evaluate the importance of engaging with course content and identify strategies to maintain interest and motivation throughout the week.
  • We will set the start in why a formalized development of software is needed.

Instructor notes

Prerequisites are:

The Pre-requirements: - Learners know basic Git - Learners know basic Python - Learners have installed necessary tools

Teaching goals are:

  • Learners can can understand why a formalized development of software is important.

Lesson Plan:

  • Total 30 min
  • Theory 20
  • Discussions 10 min

TOC

  • What is software?
    • software concepts
    • types
    • outcome
      • correct, reusable, efficient, changable
  • Example
  • SLDC

What is software?

Wikipedia

  • set of computer programs and associated documentation and data.
  • This is in contrast to hardware, from which the system is built and which actually performs the work.
  • User-written software: End-user development
    • Users create this software themselves and often overlook how important it may be to others.

Some software concepts

  • program
  • script (directly interpreted at run time)
  • tool
  • model
  • application

Info

We will not be very definite in the course in when to use scripting, program or tools.

Different types of Scientific software

  • analysis of data
    • statistics
    • figures
    • visualization
  • tools for process data
    • refining data (formatting)
    • bioinformatics
  • workflows
  • modelling (mimic the reality)
    • simulations time-varying behaviour of a system
    • mathematical models of relationships among variables in a system
  • decision assistance
  • Other

Discussion

What do you develop for?

Outcome of a Program

  • Correct
    • and flawless
  • Efficient
    • Utilize the computer system's resources
  • Reusable
    • Finished components
    • Lower development costs
    • Faster
    • Higher quality
    • packaging technology
  • Changeable
    • Maintenance cost
      • Fix errors, bugs
      • Adapt to new requirements
      • Independent modules
      • Encapsulation/information hiding

How to program?

Object oriented programming

  • Object-oriented (OO) programming is
    • a mindset of mimicking the real-world as:
    • entities (objects) that are different
    • or share attributes with each-other (within a **class**)
    • info-hiding mindset...

Objects

Elevator objects

Class

classDiagram
  class Elevator{
    +string direction
    +int floor 

    +goto_floor()
    +stop()
    + which_floor()
  }
Object orientation (OO) in some programming languages
  • OO (built-in classes)
    • C++
    • Java
    • Python
    • Julia
  • OO features
    • Fortran 2003-
    • MATLAB
    • Perl
    • PHP
  • OO object-based (but not class-based)
    • Javascript

Functional programming

  • More classical as it is more focused on the algorithms
  • Functions
  • Modules: a way to gather functions with similar functionality
  • Also to some extent info-hiding mindset

To sum up

  • At its simplest, functional programming uses immutable data to tell the program exactly what to do.
  • Object-oriented programming tells the program how to achieve results through objects altering the program's state.
  • Both paradigms can be used to create elegant code.

See also

Modular coding

  • Modular coding breaks up the code in blocks that could be separate files.
  • Modularity could be within a program but also for a workflow.

Demo: WRF module and a workflow in 'runtime'

Code Example

Exercise: Problems with this code? 7 min

Breakout room, 3-4 people, 7 minutes

Planet application

  • Review this code that simulates the Earth's change of orbit due to the interaction with other planets
  • This was done in Python with no thought of best practices, just trying to solve the problem!
  • Discuss the needs below
  • What are the problems?

  • What can be improved

  • Reusable

    • Finished components
    • Lower development costs
    • Faster
    • Higher quality
    • packaging technology
  • Changeable
    • Maintenance cost
      • Fix errors, bugs
      • Adapt to new requirements
      • Independent modules
      • Encapsulation/information hiding
  • Correct Skip this for now!
    • and flawless
  • Efficient Skip this for now!
    • Utilize the computer system's resources
planet.py 
#planet
import numpy as np
import matplotlib.pyplot as plt 

#constants
G=6.6743e-11
AU=149.597871e9 # 1 astronomical unit (AU) is the mean distance between su
AU1=150.8e9
mj=5.97219e24
mJ=1.899e27
M=1.9891e30
day=86400;
year=31556926;
v0=AU*2*np.pi/year;
Fg=G*M*mj/AU**2
ag=Fg/mj
Fc=mj*v0**2/AU
ac=Fc/mj

L=2

x0=AU1;
y0=0;
u0=0;
x=np.zeros(365*L, dtype=float);
y=np.zeros(365*L, dtype=float);

x[0]=x0;
y[0]=y0;
u=u0;
v=v0;

for i in range(1,365*L):    
    print(i)
    x[i]=x[i-1]+day*u;
    y[i]=y[i-1]+day*v;
    ax=-G*M/(abs(x[i]**2+y[i]**2)**[3/2])*x[i];
    ay=-G*M/(abs(x[i]**2+y[i]**2)**[3/2])*y[i];
    u=u+ax*day;
    v=v+ay*day;

rj=(x**2+y**2)**.5
a=max(rj)
b=min(rj)
e=1-2/(a/b+1)
rel=(a/b-1)


fig=plt.figure(1,figsize=(12,5))
ax=fig.add_subplot(1,2,1)
ax.plot(x,y)
ax.plot (0,0,'o')
#axis equal

ax=fig.add_subplot(1,2,2)
ax.plot(range(0,365*2),rj)

plt.savefig('../Figures/planet_earth.png', dpi=100, bbox_inches='tight')

Software Development Life Cycle (SDLC)

  • We need a workflow in our programming projects!

Some common steps

  • Planning
    • Analysis and design
  • Development
    • Source control
    • Algorithms
    • In-code documentation
    • Optimization
      • Parallelism
    • Tests

  • Deployment and maintenance

    • Documentation
    • Reproducibility and sharing
      • Packaging and dependencies

  • ... and Iterations

  • Agile development

    • Division of tasks into short phases of work and frequent re-assessment and adaptation of plans.

Summary of Introduction

  • Now after the overview you are ready to dig deeper about the tools!

Keypoints

  • A program shall be or have content/components that is:

    • Correct
    • Efficient
    • Reusable
    • Changeable

  • Software development is both series of steps:

    1. Requirements
    2. Analysis and design
    3. Development
    4. Test
    5. Deployment and maintenance
  • ... and iteration of these