Jeff Armstrong
President at Approximatrix, LLC
Westlake, Ohio, United States
Summary
🤩
Rockstar🎓
Top SchoolJeff Armstrong is a technically deep president and principal developer with 15+ years building numerical and scientific software, blending expertise in CFD, econometrics, multithreading and low-level systems in languages from Fortran and C to Java and Python. As founder of Approximatrix he has translated advanced math and control theory into production-grade code for aerospace and controls applications, and contributed substantive backend improvements to high-profile open-source projects such as SciPy and Open Watcom (including Schur decomposition sorting, discrete LTI support, and C99 math functions). He is comfortable across the stack of algorithm design, LAPACK integration and signal-processing tooling, and has a track record of adding rigorous tests and numerical solvers like TRSYL to shared libraries. With graduate training in mechanical engineering and economics and hands-on aerospace experience, he combines theoretical rigor with practical engineering judgment. Based in Westlake, Ohio, he also brings unconventional leadership lessons from coaching high-school varsity soccer, reflecting a collaborative, mentoring approach to technical teams.
15 years of coding experience
10 years of employment as a software developer
MS, Mechanical Engineering, MS, Mechanical Engineering at Case Western Reserve UniversityMA, Economics, MA, Economics at Cleveland State University
Github Skills (14)
numpy10
algorithms10
scipy10
c-programming10
python10
linear-algebra10
scientific-computing10
signal-processing10
compiler-development10
lapack9
error-handling9
data-analysis8
posix7
posixct7
Programming languages (9)
Github contributions (5)
open-watcom/open-watcom-v2
Oct 2013 - Jan 2023
Open Watcom V2.0 - Source code repository, Wiki, Latest Binary build, Archived builds including all installers for download.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:142 commits, 22 PRs, 31 pushes in 9 years 5 months
Contributions summary:Jeff primarily focused on enhancing the Open Watcom C/C++ compiler's math library by implementing new math functions, including the error function (erf), complementary error function (erfc), and the logarithm of the gamma function (lgamma). They also worked on improving the existing library by fixing errors and ensuring compatibility with both 16-bit and 32-bit targets. Furthermore, they added new functions such as remquo, and incorporated C99 math error handling and standard library functions.
installersbuildscode-repositorywatcomwiki
scipy/scipy
Apr 2011 - Feb 2012
SciPy library main repository
Role in this project:Backend Developer & Data Scientist
Backend Developer & Data ScientistContributions:9 commits, 1 comment in 10 months
Contributions summary:Jeff implemented features for the Schur decomposition routine, adding sorting functionality based on eigenvalue properties, as well as fixes to existing code. They added zeros-poles-gain support to discrete LTI functions, enabling new representations and functionality. The user also enhanced the signal processing module, adding discrete LTI systems, and continuous-to-discrete transforms. They further exposed LAPACK's TRSYL Sylvester equation solver and added tests.
scipypythonscientific-computing
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