ALICE vs. CPM Scheduling, a primer:

At ALICE, we often get asked the question: “How is ALICE different from CPM Scheduling?” or “How is ALICE different from Primavera P6?”. In this post, we address some of the main ways in which ALICE is unique.

At ALICE, we often get asked the question: “How is ALICE different from CPM Scheduling?” or “How is ALICE different from Primavera P6?”. In this post, we address some of the main ways in which ALICE is unique.

Some historical context

Despite the fact that it was introduced in the 1950s and has barely evolved in the last few decades, Critical Path Method (CPM) Scheduling is still one of the most widely used scheduling techniques in construction today. This scheduling technique is used to plan and control a project and to calculate the minimum completion time for the project, along with the possible start and finish times for project activities. 

 


While this technique seemed adequate in the absence of more sophisticated alternatives, the fact is that it has failed to adapt to the increasing scale and complexity of modern projects (especially mega projects).

As a result, planning and scheduling shortcomings are a contributing factor to budget overruns and schedule delays on a vast majority of large projects.

So let’s break down some of the key differences between the way ALICE works and the traditional CPM scheduling method.

ALICE: more than scheduling software

First and foremost, it is important to note that ALICE is much more than scheduling software. ALICE is a comprehensive construction simulation and optimization platform, of which one of the outputs is fully resource-loaded schedules. In that sense, it is unfair to even compare ALICE with traditional CPM scheduling software such as Primavera P6 or Microsoft Project. But since people asked, we are here to answer.

Perhaps the most fundamental difference is in how the methods are used.

In traditional CPM scheduling, your objective is to create a schedule. You take a look at some drawings to understand what you’re building, and start transferring your understanding of the project into individual tasks. You then add precedence logic and durations for each task, repeat hundreds of times, and at last, you have a single schedule.

Automatic schedule creation

ALICE is quite different. You start by defining an objective (e.g.: “I want to create an early master plan for my project” or “I want to figure out my crane strategy”).

You then bring all the necessary information in one place, such as your 3D model (if you have one, but it’s not necessary), your labor, equipment, material quantities and costs, production rates, etc. and finally you assign sequence logic to create what we call “recipes.” From that point on, ALICE automatically generates fully resource-loaded schedules for you, alongside a 5D representation of your project (3D + cost + time).

 

Recipes contain all the information required for ALICE to understand how to complete elements of your construction project (labor, material, equipment, durations, production rates, etc.)

Ease of rescheduling

Because ALICE is parametric, exploring new scenarios and rescheduling take minutes instead of days or weeks. All the user does is to define new parameter values (e.g.: adjust the number of available crews, or change productivity rates based on how a project is actually progressing) and click a button whenever they want to reschedule.

“It could take you weeks or months in P6, what ALICE can do in seconds"

Ifan Williams Senior Projects Control Scheduling Manager at Parsons Corporation

Bringing transparency to the process

In P6, it is impossible to know whether your schedule is a good schedule. Why? Because it is the only one you have and you have nothing to compare it with. Secondly, it’s very difficult to assess. On what criteria? It is hard to peel the layers of the onions and to compare alternatives.

But the most notable difference is that P6 and traditional CPM scheduling software make it possible to create infeasible schedules. How so?  In conventional CPM software logic, ties are built manually, and therefore it is 'allowed' to create broken logic, e.g. a cyclical precedence relationship between activities. In most cases, the software will give a warning or notification to the user, but nonetheless the schedule is intact and can be presented to clients. On this basis, assessing schedule quality becomes very challenging, as deciphering all these logic links and the assumptions behind them is almost impossible to do.

Moreover, due to the fact that CPM schedules are very rarely resource loaded, one can never be certain that the schedule logic would be sensible when adding resource limitations to the schedule.

Because ALICE is a parametric platform that takes every single data point and constraint into account, ALICE does not allow you to build with the wrong logic and generate infeasible schedules. So when you let ALICE crunch the numbers, your team can rest assured that the results are correct and sound without breaking any constraints. This is a huge improvement from a de-risking perspective. Furthermore, ALICE resource-loads the schedules it generates.

All in all, ALICE as a system takes into account a superset of constraints as compared to traditional CPM software, which governs everything with precedence. ALICE schedules are built on resource and sequence logic that satisfies the limitations the user has defined. Moreover, the solutions generated by ALICE are tied to the design and cost elements, making the schedule an even more insightful tool for decision making.

In brief, ALICE crunches a lot more complex data and ... does it right. Therefore the schedules generated are always correct. You might not like them, but they are calculated correctly.

From one scenario to millions

Mathematically there are thousands and thousands of ways to build a project, even with the simplest design. The options and construction strategies are vast.

With CPM scheduling, the user is predefining the sequence of work as part of the process i.e. adding precedence. In that way, without even realizing it, one is locking themselves in a particular solution (sequence), i.e. let's do A->B->C. But what if B->A->C was a more efficient sequence?

Traditional CPM simply does not allow you to gain visibility into these other options, let alone enable you to answer the above questions. To illustrate the point, to explore one or two more sequences usually results in an extra 2-3 months of work. So it makes sense that no additional construction options are explored; the unit economics do not allow it.

In contrast ALICE -- utilizing a parametric schedule model -- is able to explore a vastly broader set of solutions, and through optimization it displays the 'best' of them to the user. Notice that I used plural? Exactly. ALICE with a single optimization run will give you many solutions and different options to choose from. The platform did the crunching for you. All you need to do is analyze and learn from it.

A unique visual interface

Another fundamental difference is the visual nature of ALICE vs. the spreadsheet-like interface of P6, MS Project and other traditional CPM scheduling software. 

With ALICE, project teams can gather around a fully resource-loaded 5D model, which greatly improves collaboration. Humans are visual creatures, so having an interface that allows them to plan visually greatly reduces the chances of mistakes and miscommunication. In fact, research largely indicates that waste during the construction phase is largely caused by pre-construction preparations. Leveraging a modern visual planning platform like ALICE can solve these issues.

In conclusion, the differences between ALICE and CPM scheduling are vast. ALICE offers significant advantages over traditional CPM scheduling methods, both in terms of process and output. While traditional fixed CPM scheduling constrains you to manually create a single, non-optimized schedule, ALICE’s AI-powered platform allows teams to explore the entire universe of possibilities and automatically generates the most efficient schedule for your project.

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