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Introduction

This project serves as a basic template for developing multithreaded c++ code using the OpenMP library, as well as some notes from the thinkos.pdf textbook.

A copy of the thinkos.pdf is included in this repository.

The various building option refer to the compiler options described in thinkos.pdf textbook, chapter 1.

Building and Executing

The code can be built into an executable using a variety of ways.

All ways require the clang++ compiler included with llvm 9.0: llvm releases webpage

Plain

Using the clang++ compiler included with llvm 9.0.

  1. Create executable
clang++ main.cpp -o openmp-example -fopenmp -L/usr/local/opt/llvm/lib
./openmp-example
  1. Add optimization flag
clang++ -O main.cpp -o openmp-example-O -fopenmp -L/usr/local/opt/llvm/lib
clang++ -O1 main.cpp -o openmp-example-O1 -fopenmp -L/usr/local/opt/llvm/lib
clang++ -O2 main.cpp -o openmp-example-O2 -fopenmp -L/usr/local/opt/llvm/lib
clang++ -O3 main.cpp -o openmp-example-O3 -fopenmp -L/usr/local/opt/llvm/lib
  1. Generate object code
clang++ main.cpp -c
  1. Generate assembly code
clang++ main.cpp -S
  1. Execute preprocessor only
clang++ main.cpp -E > main.E

cmake project

Requires that cmake be installed: cmake download page

then, simply

cmake CMakeLists.txt
make -Bj16

If you plan on using standard library functions, Qt Creator sometimes gets confused about which c++ lib to use. Specify this as an include flag:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -I/usr/local/opt/llvm/include/c++/v1/")

qmake project

Requires that qt be installed using homebrew like so:

brew install qt5

or

brew upgrade qt5

Followed by

brew link qt5 --force

After that, in a command line run:

qmake q-openmp-example.pro
make -Bj16
q-openmp-example.app/Contents/MacOS/q-openmp-example

In Qt Creator, Need to open the q-openmp-example.pro file, with a kit that uses the clang++ compiler.

Telling cmake about qt5

cmake worked smoothly here in Qt Creator, b/c no QT libraries were actually used.

However, Qt Creator can have a hard time finding installed QT libraries: homebrew configuration issue

This can be solved by creating some symbolic links in /usr/local/:

sudo ln -s /usr/local/Cellar/qt/5.13.2/mkspecs /usr/local/mkspecs
sudo ln -s /usr/local/Cellar/qt/5.13.2/plugins/ /usr/local/plugins

QT libraries could have been incorporated in the CMakeLists.txt file using this syntax:

find_package(Qt5 REQUIRED COMPONENTS Core Widgets)

thinkos.pdf textbook notes

Notes from the textbook.

Memory Segments

(low number memory addresses)
C --> "Code" or "Text", actual program stored in memory
C --> "Constant": string literals
G --> "Global": global variables, declared with "static" keyword
H --> "Heap" dynamic memory allocation. Grows up towards stack
S --> "Stack" auto allocation/deallocation
(high number memory addresses)

Other Definitions

MMU = memory managament unit
TLB = translation lookaside buffer (for page number, page is chunk of memory)

given VA (virtual address), determine page # + offset --> produce PA (physical address)

MCU --> main memory

"inode" --> index node

os thinks of long-term memory as "blocks"

floating point numbers

(−1)^s * c * 2^q