The logic behind the course planner

Credit hours vs. difficulty points

Every course in the planner carries two numbers. One of them is official and on display. The other works quietly in the background, and it is the reason the auto-arrange feature can do anything useful.

Credit hours are the official figure. They count toward the 128 credits you need to graduate, and they are what the progress bar and the per-semester credit totals report.

Difficulty points are an estimate of how much work a course is, which is a different question from how many credits it carries. A three-credit thermodynamics course and a three-credit elective look identical on a transcript, but they do not take the same toll on a given week. Difficulty points let the planner even out that real workload across your semesters instead of just evening out credit counts. You never see a difficulty-point number anywhere in the tool. What you see is the balanced plan it produces, plus a plain difficult or very difficult label on the heavier courses.

A course's difficulty points are its credit hours times a factor that depends on its tier:

General-education courses sit a little under a full credit hour for two reasons. They tend to be lighter at the same credit count, and the small discount also lets the auto-arranger tell a gen-ed apart from a major course of the same weight when it has to break a tie. Every other course is placed in one of the three tiers above, assigned by hand.

Senior design is weighted on purpose

Senior design gets a higher weight that is set by hand rather than read off the tiers above. Capstone design is mostly project work, and the team meetings, prototyping, and testing that go into it eat up far more time than three credit hours would suggest, most of it outside of class. To leave room for that, the planner counts Senior Design I as twice its credits and Senior Design II as three times its credits, which pushes the auto-arranger to keep the rest of the senior year on the lighter side.

Because these weights are plain multiples of credits, senior design does not belong to a difficulty tier and carries no difficulty label, so you will not see one on it. The extra weight is just a way to nudge the auto-arranger, not a claim that the course is academically harder than anything else in the curriculum.

The recommended plans

The planner starts from the department's recommended four-year sequences, one for the standard track and one for the pre-med track, both matching the official flowcharts. From there, you can rearrange courses by hand, mark off work you have already finished (AP and transfer credit included, which are automatically marked as completed), and add summer semesters or a fifth and sixth year.

The recommended sequence is also the layout the auto-arranger leans back toward when nothing else argues for moving a course. The rest of this page is about what the auto-arranger does.

The auto-arranger

The Auto-arrange button takes every course you have not yet finished and drops it into the semesters you have open. It does not shuffle the flowchart or fall back on rules of thumb. It works the whole plan out from scratch, searching through the valid arrangements for the one that scores best against the priorities laid out below.

It works from wherever your plan already is. Anything you have marked complete stays put and counts as a prerequisite for what comes after it, and any semester you have opened is fair game, summers and extra years included. From there, it treats the job as two layers: a set of rules it will not break, and a set of preferences it balances as well as it can.

Rules it never breaks

These are hard constraints. The auto-arranger will not return a plan that violates any of them:

• Prerequisites. A course is always placed in a later semester than every prerequisite it requires.
• Corequisites. A course is placed in the same semester as its corequisite, or later.
• Semester availability. A course only lands in a semester it is actually offered in, according to the catalog, whether that is fall, spring, or summer.
• Senior design sequence. Senior Design I and II are always back to back, fall then the following spring of the same year.
• Junior/senior standing for design electives. A design elective is only placed once at least 60 credits have been earned in earlier semesters (counting AP and transfer credit).

Because these are enforced directly, the resulting plan is always internally valid. The same checks that flag a problem when you drag a course into the wrong place come up clean after an auto-arrange.

What it balances, in order

Everything that is a preference rather than a hard rule is rolled into a single score. A plan picks up penalty points whenever it falls short of one of these preferences, weighted by how much that preference matters, and the auto-arranger hunts for the valid plan with the lowest total. In practice, that sets up a priority order: when two preferences pull in opposite directions, the stronger one wins. Strongest first:

How the optimization works

Laying out a few dozen courses across up to about a dozen semesters opens up an astronomical number of possible arrangements, far too many to check one at a time. Rather than guess, the planner solves the problem exactly, with a method called mixed-integer linear programming.

The whole problem gets turned into math. Every question of the form "does this course go in this semester?" becomes a yes or a no, written as a 1 or a 0. The hard rules become equations and inequalities those answers have to satisfy, and the scorecard above becomes a single number to drive as low as possible. A solver then chews through all of it. The planner uses HiGHS, a well-regarded open-source optimizer. It does not look at every arrangement one by one. It uses mathematical bounds to rule out entire families of options that cannot beat the best one it has already found, throwing them out in bulk, and that is how an otherwise impossible search finishes in a few seconds.

A few things follow from doing it this way:

• It is effectively optimal. The solver stops as soon as it can prove the plan is within a small margin, about 5%, of the theoretical best. That trades a little quality for a lot of speed, and for arranging courses, the result is indistinguishable from optimal.
• It is deterministic. The same starting plan always produces the same result. Nothing about it is random.
• It handles a late start or a fifth year. The "stay close to the recommended sequence" preference looks only at where a course sits relative to the rest of your plan, not at the calendar year it falls in. If you begin partway through the sequence or spread the degree over five or six years, the whole thing can slide together at no cost. Only real reorderings get charged.

Current settings

The table below lists the planner's main settings and the values they are set to now.

Other design decisions

Gen-eds and electives float freely

Humanities, social science, art, free electives, technical electives, design electives, and the English-composition courses are not tied to their flowchart position. Where they fall in the sequence does not carry the academic meaning that the core science and engineering chain does, so the auto-arranger can put them wherever balances the plan best. It still respects their hard rules, like the 60-credit gate on design electives and the prerequisite tying the two English courses together. The core STEM courses, by contrast, are gently biased to stay close to their recommended order.

Summers are relief valves

The auto-arranger never puts courses into a summer on its own. Opening a summer semester is a deliberate move on your part. Once one is open, though, it becomes the preferred place to offload work, which is what makes genuinely lighter fall and spring semesters possible. With no summer semester at all, the eight regular semesters are already close to full just to fit a complete degree, so there is not much room to lighten any single one of them.

The pre-med track

The pre-med track carries a different course set. It adds the medical school prerequisites and gives up the free and technical electives to make room, and it brings in the timing preference described above so those prerequisites land before the MCAT window. Everything else about the auto-arranger is the same.

Difficulty flags you do see

Although the point values stay behind the scenes, each course's tier still shows up as a small flag on difficult and very difficult courses, and each semester shows a count of how many heavy courses it holds. That gives you a quick read on whether a semester is loaded with hard material.

Scope, privacy & caveats