Personal blog on early retirement, selling tradelines, and analytics projects. I write about what I learn as I am learning it.
The staff scheduler I wrote about a few weeks ago was a MILP — a Mixed Integer Linear Program. You define variables, constraints, and an objective function. Hand it to a solver, get an answer. Clean, relatively tractable, runs in seconds on a laptop.
The vehicle routing problem is something else entirely.
When you convert an optimization model from Excel to standalone Python, you expect to do some work. You expect to rewrite the data loading, restructure the variable definitions, test the output. What you don’t expect is for the model to fail in three distinct ways, each one caused by something the Excel version was handling silently without you knowing it.
That’s what happened here. Three bugs. All real. All the kind that would have stayed invisible forever if the model had stayed in the spreadsheet.
Continue reading “Three Bugs That Would Have Stayed Hidden in Excel”PuLP is a Python library for writing optimization models. MILP stands for Mixed Integer Linear Program. CBC is an open-source solver. Together, they’re what makes the Staff Scheduler work — and together, they represent something I find genuinely interesting: the fact that problems that used to require expensive commercial software and specialized hardware can now be solved on a laptop, for free, in a few seconds.
Let me explain what’s actually happening under the hood.
Continue reading “PuLP, MILP, and CBC: The Alphabet Soup Behind Your Schedule”“How many days in five months” is a very strange question to write a post about but I am learning about SEO (Search Engine Optimization). And using Ahrefs keyword research tool I found out the question is a very good keyword to target. At the end, I explain how to calculate it using Excel (or any spreadsheet).
This is what Google tells us:
Have you ever experienced the frustration of working on a large Excel spreadsheet, only to have Excel crash and display the message “Excel ran out of resources”? This message can be caused by several factors, and it can be a real pain to figure out which one is the culprit. In this post, we’ll provide you with a list of possible causes, explain how to check if those causes are the problem, and share some best practices to prevent this annoying issue.
