Coding Tidbit

January 16, 2020

C#: Never Test For NaN With Equality Test

Let's write a simple program to test. To get a NaN, we do a 0/0 and store it in num. First of all, the divisor has to be a float-point type because DivideByZeroException shall be thrown for integer or decimal zero divisor. Note: Non-zero number divided by zero (float) gives an infinity number. In our […]

January 9, 2020

No Code is the Fastest Code

Optimization of finding a point with shortest distance w.r.t. a point of interest The benchmark source code is hosted at Github. Table of Contents Introduction Shortest Distance Benchmark Results History Introduction When it comes to optimization, majority of developers turn to parallelism but per CPU core isn’t cheap. We could look to eliminate some operations […]

January 2, 2020

C++14/20 Heterogeneous Lookup Benchmark

Download the benchmark code on GitHub. C++14 introduced ordered transparency lookup which enables const char* and string_view lookup without string instantiation on map/set objects. C++20 introduced unordered transparency lookup that allows to do same thing with unordered_map/unordered_set. We are officially in 2020 but as of writing time, the C++20 Standard is yet to be ratified […]

August 15, 2019

C++: Size Matters in Platform Compatibility

Introduction For file storage and data communication to work interoperably, the width of datatype must stay invariant across platforms. This tip discusses the pitfalls of platform-dependent data width and their solution. Endianess, deserving a tip of its own, is not covered here. time_t time_t stores the number of seconds since 1st January 1970. It is […]

April 1, 2019

C++23: fullptr to replace nullptr

Coming in C++ 2023, detailed in the AF0401 proposal, fullptr_t is fully recommended as the invalid pointer type to replace current nullptr_t which first standardized in C++11. nullptr is defined as a pointer value with all its bits set to zeroes while fullptr has its bits set to ones (the address of the last addressable […]

January 14, 2019

C++11 std::div() Benchmark

Download source at Github Update: rand() overhead in benchmark has been removed by filling the array with random values beforehand. C++11 standard introduces std::div() and its siblings on the premise of some compiler can take advantage of the available machine code that compute quotient and remainder of division together. The C++ reference noted, and (updated) […]

January 14, 2019

Not Every Memory Allocation Failure is OOM

Introduction As with many C++ programmers with C background, bring their C habits to C++ programming as shown in the below code where a massive array is allocated and pointer is then checked for failed allocation in presence of null address. It works this way for C malloc. Unfortunately, C++ new does not work like […]

June 7, 2018

Floating Point and Integer Arithmetic Benchmark

Introduction This is not much of a tip, just a posting of benchmark result to compare integer and floating point arithmetic timing. All the integer and floating point types used in Benchmark are 64bit. Timing is based on looping 100 million times. Clarification: SmallInt and SmallDouble refers to small values (10-10000) stored in int64_t and […]

June 6, 2018

C++: Simple Permutation and Combination Parallelism

Primary Motivation Single Threaded Permutation Multi-Threaded Permutation Single Threaded Combination Multi-Threaded Combination Primary Motivation My Github repository, Boost Concurrent Permutations and Combinations on CPU, has been up since January 2017. However, download is close to none while my older single threaded next_combination has plenty of downloads. So I figured it must be the code usage […]

June 6, 2018

Improved Next Combination with State

To speed up next_combination, we can store the state of generated combination so that it does not have to find which current combination elements correspond to the bigger collection. One way to do it is to store this state inside a class but this violates the design of STL algorithms. Another way to do it, […]