Self-Assessment Quiz: The Fortran Ecosystem

Twenty questions to confirm you can navigate the ecosystem before Part IV. Aim for 16 or more. Answers and a topic map are at the end — try the whole quiz first.

Question 1

LAPACK and BLAS are written primarily in which language? - A. C - B. Fortran - C. Assembly - D. Python

Question 2

In the BLAS level scheme, a matrix-matrix multiply (gemm) is a: - A. Level-1 operation (vector-vector) - B. Level-2 operation (matrix-vector) - C. Level-3 operation (matrix-matrix) - D. Level-0 operation (scalar)

Question 3

Decode the LAPACK routine name dsyev. - A. Double, symmetric, eigenvalues/eigenvectors - B. Double, general, solve - C. Single, symmetric, SVD - D. Double, Hermitian, factorize

Question 4

LAPACK is written once, portably, yet runs fast on many chips because: - A. It is recompiled from scratch for each machine by the user - B. It calls the BLAS interface, and whichever tuned BLAS is installed supplies the fast kernels - C. It contains hand-written assembly for every processor ever made - D. It runs only on supercomputers

Question 5

The reference BLAS from Netlib is slower than OpenBLAS or MKL because the tuned versions: - A. Compute a less accurate answer - B. Use cache blocking and hand-issued vector instructions for the specific hardware - C. Skip most of the arithmetic - D. Are written in Python

Question 6

FFTW is a library for: - A. Solving linear systems - B. Fast Fourier transforms - C. Writing HDF5 files - D. Message passing

Question 7

Which two formats are the standard, portable, self-describing containers for large scientific datasets? - A. CSV and JSON - B. NetCDF and HDF5 - C. TXT and XML - D. ZIP and TAR

Question 8

MPI is best described as: - A. A single Fortran library you use - B. A standard/specification with several implementations (MPICH, Open MPI, …) for message passing - C. A compiler - D. A file format

Question 9

fpm stands for, and is: - A. "Fast Program Maker," a profiler - B. "Fortran Package Manager," a build tool and dependency manager driven by fpm.toml - C. "Formatted Print Module," an I/O library - D. "Fortran Physics Model," a solver

Question 10

In an fpm project, a program unit that should become the executable belongs in which directory? - A. src/ - B. test/ - C. app/ - D. bin/

Question 11

Which fpm command builds (if needed) and runs the executable? - A. fpm compile - B. fpm exec - C. fpm run - D. fpm start

Question 12

A git dependency in fpm.toml must be written as: - A. A bare string: stdlib = "https://…" - B. An inline table: stdlib = { git = "https://…" } - C. A list: stdlib = ["https://…"] - D. A comment

Question 13

stdlib is: - A. Part of the ISO Fortran standard, always available - B. A community-developed standard library (stats, sorting, strings, I/O, math) you depend on as a package - C. A replacement for gfortran - D. A text editor

Question 14

A program using use stdlib_stats, only: mean will not compile with a bare gfortran file.f90 because: - A. mean is a reserved word - B. The stdlib_stats module must be compiled and linked first (fpm handles this) - C. gfortran cannot compile functions - D. stdlib requires Python

Question 15

fortls is: - A. A file-listing command - B. The Fortran Language Server — editor autocomplete, go-to-definition, live diagnostics via LSP - C. A LAPACK routine - D. A build system

Question 16

FORD is a tool that: - A. Runs unit tests - B. Generates browsable HTML documentation from source and special !!/!> comments - C. Manages dependencies - D. Profiles code

Question 17

pFUnit is: - A. A plotting library - B. A unit-testing framework for Fortran (parallel-capable, from NASA Goddard) - C. A package registry - D. A Fourier transform library

Question 18

True or false: adding FORD documentation comments (!!, !>) can break your program's compilation.

Question 19

For a brand-new Fortran library where you control the layout, the lowest-friction build system is: - A. A hand-written Makefile - B. CMake - C. fpm - D. Meson

Question 20

What does this print?

real(dp) :: x(4) = [2.0_dp, 4.0_dp, 6.0_dp, 8.0_dp]
print '(a, f6.2)', 'mean = ', sum(x) / real(size(x), dp)
  • A. mean = 4.00
  • B. mean = 5.00
  • C. mean = 20.00
  • D. mean = 2.50

Answer Key

Q Ans Why
1 B LAPACK and BLAS reference implementations are Fortran — the floor is Fortran.
2 C Matrix-matrix (gemm) is Level 3; $O(n^3)$ flops on $O(n^2)$ data.
3 A double · symmetric · ev = eigenvalues/eigenvectors.
4 B Portable LAPACK calls the BLAS interface; the installed tuned BLAS supplies speed.
5 B Same answer, but blocked for cache and hand-vectorized for the chip.
6 B FFTW = Fastest Fourier Transform in the West.
7 B NetCDF and HDF5 are the portable, self-describing scientific formats.
8 B MPI is a standard with multiple implementations.
9 B Fortran Package Manager; manifest is fpm.toml.
10 C app/ holds programs (executables); src/ the library; test/ tests.
11 C fpm run.
12 B A git dependency is an inline table with a git key, not a bare string.
13 B stdlib is a community package, not part of the ISO standard.
14 B The module must be built/linked first; fpm does that via the dependency.
15 B fortls is the Fortran Language Server (LSP).
16 B FORD generates HTML docs from source + doc comments.
17 B pFUnit is a (parallel-capable) unit-testing framework.
18 False Doc markers are ordinary comments; the compiler ignores them.
19 C fpm is the least friction for new projects.
20 A $(2+4+6+8)/4 = 20/4 = 4.00$; f6.2 prints 4.00.

Topics to review by question

  • Q1–5 → §16.1 (LAPACK/BLAS, the levels, separation of concerns, tuned vs reference).
  • Q6–8 → §16.2 (FFTW, NetCDF/HDF5, MPI).
  • Q9–12 → §16.3 (fpm: layout, commands, dependency syntax).
  • Q13–14 → §16.4 (stdlib and why it needs fpm).
  • Q15–19 → §16.5 (fortls, FORD, pFUnit, build systems).
  • Q20 → §16.4 / Chapter 5 (array intrinsics; also hand-computed output).

Scored below 16? Reread the flagged sections. The one idea worth over-learning is §16.1's separation of concerns — it explains why you call tuned libraries instead of hand-optimizing, a theme that returns in Chapter 21 and Chapter 29.