Personal blog. I write about what I learn as I am learning it

Security Guard Scheduling Software (Free)

Most security guard scheduling software is built for a company running dozens of sites and dozens of guards, and it prices itself accordingly. A single post that just needs to be covered 24 hours a day with a small team doesn’t need any of that — it needs a rest rule, a rule against a day shift the morning after a night, and someone to spread the weekends around fairly. This is a free tool built for exactly that smaller, sharper version of the 24/7 problem, with a solver underneath it instead of a template.

Bar chart: clustering penalty cuts lone single-day shifts from 27 to 3 on a 3-week, 7-guard security roster, identical coverage — Same 7-guard roster, same coverage — one penalty is the difference between 27 lone shifts and 3.

Nurse Scheduling Software (Free, No Signup)

Search for nurse scheduling software and most of what comes up wants a signup and a credit card before it shows you anything. This one doesn’t, and it’s built for the part of nurse rostering that actually breaks ordinary scheduling tools: a ward runs 24 hours a day, so the rest rule, the consecutive-nights cap, and the no-day-after-a-night rule all have to reach across midnight — a boundary a day-by-day template has no way to see at all.

Bar chart: clustering penalty cuts single-shift blocks from 74 to 14 and day-night switches from 23 to 11 on a 28-day, 16-nurse ward roster, same coverage — Same coverage, same labour cost — whether the roster is livable or not comes down to one extra rule.

Construction Schedule Delay Analysis: I Tested Every Task

Construction schedule delay analysis almost always starts from the same document: the float table. Which activities had slack, how much, and therefore who owes whom the days. It is the number that decides whether a delay was excusable, concurrent, or somebody’s fault, and it is on the front page of every claim I have ever read.

So I tested it. I took a 21-task renovation with three general crew, delayed every single task a day at a time, and re-solved the whole schedule after each one to see when the finish date actually moved. Twenty-one tasks, a few hundred solves. Three of them turned out to have nine days of float on paper and no tolerance at all.

Paired bar chart of twelve renovation tasks comparing total float with the delay each can actually absorb; roofing, driveway and landscaping each show nine days of float and zero days of tolerance. — Every task was delayed a day at a time and the whole plan re-solved. Grey is what the float table promised; blue is what survived contact with three crew.

Resource Leveling Techniques, and Why Yours Guesses

Search for resource leveling techniques and you get lists: level within float, delay non-critical tasks, split tasks, reassign resources, adjust the calendar, fast track, add people. All real things you can do. None of them is what the button in your scheduling software is actually doing when you press it, and the gap between the list and the button is why two tools level the same plan and hand you two different schedules.

Underneath, there is one technique with two moving parts, and a lot of arbitrary choice in the second part. Here is what it did to a 21-task renovation.

Horizontal bar chart of the eleven tasks leveling pushed later, from Driveway and Landscaping at 14 working days down to six tasks at 3 days each. — Five of the eleven tasks that moved had no CPM float at all. A technique that only shifts slack tasks cannot produce this schedule.

Continue reading “Resource Leveling Techniques, and Why Yours Guesses”

Resource Loading: The Chart Under the Gantt Chart

A resource loading chart is the histogram that sits under a Gantt chart: for each day of the plan, how many people that day needs. It is the least glamorous drawing in project management and the only one that ever told me anything I did not already know from looking at the bars.

Here is one for a 21-task house renovation, before and after the schedule was made to fit inside the crew that actually exists. The two panels hold exactly the same amount of work.