Fortran Programming for Scientific Computing: A Beginner's Guide, Slides of Mechanical Engineering

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• INTRODUCTION

History of Fortran…

1. 1 st^ version: 1950’s…IBM

2. Fortran 66…

3. Fortran 77…

4. Fortran 90…fairly big changes but…

Fortran

Fortran

• Usually much harder
  • example: weather forecasting (numerical weather prediction, NWP)
  • Involves simultaneous solution of multiple equations at multiple locations in the atmosphere at multiple times to get a forecast

• Solving a scientific/engineering problem

ALWAYS involves many steps.

• Many of these steps do not involve Fortran!!!
• So we will learn much more than just Fortran

in this class!

• The first step is to do as much work as

possible on paper

• make sure you have defined the problem properly
• make sure you have as much information as possible

• Example: Suppose we wish to calculate how

much kinetic energy is in hurricane Irene.

• Think first about how you would do this with pen and pencil.
• Recall that kinetic energy is defined as:

(speed)^2 /

• Now we can take real wind data (e.g., from research aircraft, forecast models etc.) and compute “K” using our formula.
• Computers are VERY good at these tasks.
  • Note that wind speed could be both horizontal winds (“large” numbers) and vertical winds (“small” numbers)

• The next step is to break the calculation down

into small bite-sized pieces.

• Typically we do this on paper (or in your head

when the problem is easy AND you have lots

of experience)

• In our KE example…

• And now - translate each step in the list above

into Fortran!

• This is like translating into Spanish.
• You need to know two things:
  • Vocabulary
    • Words like: IF, STOP, GO TO, PRINT » They all look pretty obvious!
  • Rules
    • Things like: the commands “STOP” and “END” must appear in your program.

• Computers are very smart!
  • They can do many things
    • they can remember lots of stuff (via memory)
    • they are VERY fast

• Once you have your Fortran program written,

the next step is to present the program to a

computer!

• If you are on a laptop with Fortran software

installed, this will be straightforward.

• If you are on a department machine (including

laptop), there are extra steps…see later.

• Computers are very dumb!
  • They don’t know what Fortran is!
  • They have to translate your Fortran program into a low-level machine language. - Fortran is machine-independent. - Machine language is machine-dependent.

• The compiler digests this and produces an executable file – a file called program.exe
• This is what then “runs” on the computer to solve your problem (e.g., make a forecast)

Putting it all together…

• With a computer that has Fortran software

installed, you would:

• Open up the Fortran software (just like opening up Word)
• Type in your Fortran code using a text editor
  • MS Word is a very fancy text editor; we use simpler ones (see later)