A transient heat-transfer run in PrePoMax can keep a workstation busy for most of an hour. During that hour the machines around it, a colleague's desktop or the spare workstation in the corner, mostly sit idle.
The OmnibusCloud Solver puts those machines to work on that run. It is a small program that takes CalculiX's place in PrePoMax. Point PrePoMax at it once, and the Run button sends heat-transfer analyses to the machines of your group, or of a project others have joined. The result comes back as an ordinary .frd file and opens in PrePoMax's own Results view. Everything else, a static stress analysis for example, runs on your CalculiX as before.
How it looks in PrePoMax
You install the solver for your Windows user (no administrator rights needed), sign in, choose the group your solves go to, and paste one path into PrePoMax's solver settings. The getting started page → shows each step.
From then on, PrePoMax's monitor shows what happened to each run. A steady model that goes to the cloud looks like this:
Deck accepted: Stationary solve on a 9×9×9 node lattice.
compute target: group 'Demo Group'
job submitted: 5202048f-… (SchwarzSolve)
progress: 100%
cloud solve converged in 1 Schwarz round.A model the cloud doesn't take gets its reason printed first, and then CalculiX takes over:
Deck rejected — outside the subset the cloud solver takes:
[UnsupportedProcedure] Procedure *STATIC is not a heat-transfer solve …
falling back to local CalculiX: the analysis is outside the cloud-supported subset (see above)The same applies when you're offline, signed out, or your group isn't available: the analysis is computed locally, with the reason printed. Kill in PrePoMax stops waiting for a cloud job without cancelling it. Press Run again and the solver picks that job up; if you changed the model in between, it cancels the old job and solves the new one.
What it solves today
The cloud takes heat conduction with temperature as the one field. The table shows where each kind of model runs:
| Solved in the cloud | Runs on your CalculiX | |
|---|---|---|
| Analysis | heat transfer, steady or transient, one step | static, modal, buckling, dynamic, coupled thermal-structural; anything with more than one step |
| Geometry | 3D solids, plane 2D, axisymmetric; structured meshes exactly, other meshes sampled onto a grid | box meshes with uneven spacing |
| Loads | prescribed temperatures, surface heat flux, volumetric sources (also varying in time), convection | films or prescribed temperatures that change during a transient |
| Radiation | to a fixed ambient temperature, steady state | between surfaces (view factors); during a transient |
| Materials | constant conductivity; conductivity that depends on temperature, steady state | density or specific heat that depend on temperature; anisotropic conductivity |
| Contact | — | contact, tied surfaces, gap conductance |
Radiation and temperature-dependent conductivity are solved as a short series of linear cloud solves. To check a particular model, run it: if the cloud doesn't take it, the monitor names every keyword that kept it out.
A steady model is split into overlapping parts that several machines solve at once and then reconcile along their overlaps. A transient one is split along time: slabs of the time range advance on several machines together and are corrected until the whole history is consistent.
When it pays off
On a large transient model, 32,768 nodes and 4,000 time steps, CalculiX on a 32-core workstation took 49 minutes (its log shows it ran on one CPU). The cloud took under three minutes, about 19 times faster, with the server reached over the internet. Most of that comes from the method: for a linear heat problem the cloud solver sets the system up once and reuses it at every time step, so the more steps a run has, the more it gains. A faster pool, or an on-premise server close to the machines, leaves room for more.
Small models are a different matter. Sending a model out and coordinating several machines takes time of its own, so a steady model that your workstation solves in seconds can take longer in the cloud. For a run that short, the difference rarely matters. The cloud makes itself felt where a run would otherwise keep your workstation busy for an hour.
So the choice comes down to your practice. If heat-transfer analyses are a regular part of your work, point PrePoMax at the solver once and leave it there: whatever the cloud doesn't take still runs on CalculiX. If you rarely run them, keep PrePoMax pointed at CalculiX as it is.
How close the answers are
We checked the cloud path against CalculiX 2.22 on 21 decks from CalculiX's own example and test collection, comparing node by node. On structured box meshes the two agree to the precision of the .frd file. Transient results differ by about 3 × 10⁻⁵ relative, because the two use different time integrators.
Tetrahedral meshes behave differently, and it helps to see how before you try one. The cloud solves on a regular grid, so a model meshed with tetrahedra is sampled onto that grid, solved there and returned on it. PrePoMax then shows the grid cells. Below, a tube with a round bore came back with a stepped opening:
The temperature along the tube is right. Near curved and sloping surfaces the geometry is a first-order approximation, typically a few percent off, and every such run prints a warning about it. When that matters, point PrePoMax back at CalculiX for that model. In two cases sampling would change the problem itself, a boundary the grid never touches and a material layer thinner than one cell, so the solver refuses those and they run locally on their own.
What leaves your machine
The solver reads the analysis locally and sends only the problem it describes: the grid, materials, loads and boundary conditions. Your .pmx and the files in PrePoMax's work directory stay where they are. The problem is solved on machines of the group or project you chose, and the result comes back into PrePoMax's work directory. Sign-in goes through your browser.
The solver can also work with an on-premise OmnibusCloud server. With an office pool behind it, models and results never leave your network. If that is what your data needs, get in touch →.
Beyond heat transfer
Heat conduction from PrePoMax is the first simulation workload on OmnibusCloud. If you work with other analyses or another solver and wonder whether they could run on your team's machines in the same way, tell us about it →. We'll look at it together.
Try it
The solver is in beta, for Windows 10 and 11, tested with PrePoMax 2.5.0 and 2.6.0. You need an OmnibusCloud account and a group or project to solve on; a group made of your own machines running the OmnibusCloud client is enough to start.
- Download the solver →
- Getting started with the solver for PrePoMax →
- Getting started with private groups →
If the solver refuses a model you think it should take, post it in r/OmnibusCloud →. Every refusal names the keyword that caused it, which makes it quick to tell a gap we should close from a model that belongs on CalculiX.