I have a couple of orthogonal suggestions.
First, and you may have done this yourself, before you give any assignment you should create a reference implementation yourself and test it in the student's environment. If you did this, then just let it be a warning to others. This is true, actually, for any assignment, not just one that might run up agains limitations.
But for the current situation, simply realize that there are several ways for the students to learn, not just through successfully building software for a problem. While you might be able to change the conditions for a future offering of the course, you need to deal with today's students.
One of the most valuable educational experiences is a Retrospective of a project in which you formally explore what worked well and what needs to be changed (or should have been changed). Instead of a working program per student, a paper per student (or student group) can impart the desired learning. Students could examine the results of other students, for example, and reflect (in writing) on the relationship between the code and the outcomes.
However, if you only want an answer to the stated question (how to provide for computationally intensive projects), then you need to either scale down the exercise to make it reasonable, or you need to provide adequate resources somehow. Upgrading all the laptops is probably not in the works, but you could, perhaps, provide access to a more powerful system (or systems) on which the students all work (individually or in groups).
Scaling down the project might work, actually, at an undergraduate level, since the students aren't expected to build commercial quality software, but only enough so that the appropriate learning occurs. If this were a doctoral program, on the other hand, where the students are involved in serious research, then there doesn't seem to be any alternative to finding the resources - perhaps through grant writing or even begging resources from local organizations.
Note that Retrospectives are a fundamental Agile Software Development practice.