Many scientific computing applications consist of processing data and then writing out to disk. Often the application will be I/O bound, which means that the computation time is shorter that the time it takes to read or write data to disk. Even though modern OSes do their best to write efficiently to the hardware, there… Read More Buffering writes
One of the unexpected side-effects of our attempt to fire-break #COVID19 with #PhysicalDistancing , is the absence of laughter in the late night shows I like to watch. This lack of laughter taught me some interesting things about my reactions to these shows, and gave me extra admiration for how @StephenAtHome and @iamjohnoliver
are now doing the shows with no live feedback. … Read More Laughter, groupthink and physical distancing
Compilers have options that allow you to retain and inspect a disassembly of the generated machine code. On macOS, passing the gcc compiler the options -fverbose-asm -save-temps will tell the compiler to write out a file with the assembly code interspersed with the original source code. As an example, the file compiled with c++ -c… Read More Stream-of-consciousness note on disassembly
Using matrix multiplication as an example, we explore how computation speed is dramatically affected by how data is laid out in memory.… Read More CPU caches and data locality: a small demonstration
C++ is an object oriented language. So is Python. Python in my opinion handles most object oriented concepts much more elegantly than C++. Here is a small example. (Well, both are sold as multi-paradigm languages, which means they do a bit of everything. C++ has tail call optimization and Python has lambdas and functions are… Read More A certain awkwardness with C++ inheritance
If you define a function in a header file (i.e. have it’s implementation in the header) and statically link your program, you need to declare it inline if the header is used in multiple files. This is different from issues you get when a header file is included multiple times in a compilation unit. Consider… Read More static linking, duplicate symbol error and inlineing
Mixing up units is a very common problem everywhere. A formula takes meters, you put in feet and your Mars probe crashes. It happens. In C++ there are “zero cost” libraries to handle full-fledged dimensional checking, conversions and safeguards. How do they work? Are they really zero cost? Let’s explore using a simple limited example,… Read More Simple units checking for cheap in C++
