Getting Started with the OmnibusCloud Solver for PrePoMax

The OmnibusCloud Solver takes the place of CalculiX in PrePoMax. You point PrePoMax at it once, and from then on the Run button works as it always has. When the analysis is a heat-transfer problem the cloud can take, the solver sends it to the machines of your group or project and writes the result back as an ordinary .frd file, which PrePoMax opens in its own Results view. Any other analysis, a structural one for example, runs on your own CalculiX as before, and the monitor names the reason.

There is no plugin and no new menu in PrePoMax, and the solver never edits PrePoMax's settings.

Before you start

  • An OmnibusCloud account, the same one used on the portal and in the client. If you don't have one, you'll create it during sign-in.
  • Machines to solve on. The solver sends work only to a group or a project your account belongs to: a private group → pooling your team's workstations, or a project → others have joined with their machines.
  • PrePoMax on Windows 10 or 11 (x64). The solver is tested with PrePoMax 2.5.0 and 2.6.0.

The solver does not need the OmnibusCloud client on your machine. The client is what lends a machine to the network; the solver only sends work to it. If you install the client → as well, your workstation becomes one of the machines solving your group's jobs.

1. Install the solver

Open the Solver downloads page →. There are two installers, and the only difference is whether CalculiX travels with them:

  • OmnibusCloud Solver, the usual choice when PrePoMax is on the machine. Analyses that run locally use the CalculiX that comes with PrePoMax.
  • With CalculiX bundled, for a machine with no CalculiX of its own. It carries CalculiX 2.22, redistributed unmodified under GPL-2.0.

The installer needs no administrator rights: it installs for you alone, into %LOCALAPPDATA%\Programs\OmnibusCloud\Solver. Upgrades keep the solver in the same place, so the path you give PrePoMax stays valid.

2. Sign in

Start OmnibusCloud Solver from the Start menu. Its window opens on the sign-in screen, with a status card underneath: Cloud needs a sign-in, and Local solver uses the host's CalculiX. Until you sign in, every analysis runs on your own CalculiX.

Click Login with Browser and complete the sign-in in your browser. Back in the solver window, Account shows who the solver runs as: your name, your email and the sign-in server.

You sign in once. The session survives restarts and upgrades. Sign out clears this machine's session; until you sign in again, analyses run locally.

3. Choose where your solves run

Open Configuration and find Compute target. The list comes from the server and holds only what your account may use: your groups and your projects. The first entry, Automatic, names the one it would pick right now.

Pick a group or a project and press Save. The choice belongs to this machine's solver and applies to every analysis you run from PrePoMax. If you join a group on the portal while the window is open, the reload button next to the list fetches it again.

The solver checks the choice before every submission. If the group was renamed or you left it, the solver sends nothing, lists what you can use instead, and runs that analysis locally.

The other rows of Configuration are for scripted setups and troubleshooting. Leave them as they are.

4. Point PrePoMax at the solver

Open Host setup in the solver window. It shows the exact path PrePoMax needs. Press Copy.

In PrePoMax, open Tools → Settings → Solver and find Executable under CalculiX. In PrePoMax 2.5 the same field is under Tools → Settings → Calculix → Executable. Write down its current value first: pasting it back is how you undo this. Then paste the solver's path and press OK. This is PrePoMax's one global solver setting, so from now on every analysis goes through the solver.

After your first run, Host setup confirms that PrePoMax called the solver and where that analysis went.

5. Press Run

Build or import a heat-transfer model with a steady-state step, create the analysis, and press Run. The analysis dialog still says CalculiX; its executable is the solver now. PrePoMax's monitor opens as usual, and the solver speaks in it:

 omnibuscloud-solver 1.1.2-beta — OmnibusCloud FEA solver
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.

The solver read the model and found that it is a problem the cloud can take. It names the group the work goes to, submits the job and names the method. SchwarzSolve splits the model into overlapping parts, solves them on several machines at once and repeats until the parts agree along their overlaps. The solver writes converged only when that solve met its tolerance. If it doesn't, nothing from the cloud is written, and the analysis runs locally.

Press Results. The temperature field opens in PrePoMax's own Results view, like any CalculiX result.

Now run something the cloud doesn't take, a static stress analysis for example. The monitor names the reason by the keyword that caused it, and then plain 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)
 local solver: PrePoMax 2.6.0 that runs this solver

CalculiX's own output follows, and Results opens as usual. The solver makes this decision before it contacts the server, so the outcome is the same whether you are signed in or not, online or offline. If several things keep a model out of the cloud, the monitor lists all of them in the same run.

6. Run a transient analysis

A transient analysis uses the same heat-transfer step with Steady state off. Set its time span in the step itself: open Step → Step → Edit, set Incrementation → Type to Direct, then fill in Time period and Initial time increment.

This matters because PrePoMax 2.5 and 2.6 import a transient step with Type: Default and then write the analysis without its time data. The solver can't tell what span you meant, so that analysis runs locally as a single increment, and the monitor points you to the setting above.

Run it. The monitor now names PararealSolve: the time span is split into slabs that several machines advance together, corrected until the whole history is consistent.

Deck accepted: Transient solve on a 6×6×6 node lattice.
 compute target: group 'Demo Group'
 job submitted: 6dabebcc-… (PararealSolve)
 progress: …
 cloud solve converged in 5 parareal corrections.

The result is a time series with the same moments CalculiX would write for this analysis: every increment by default, or every Nth if you set Output frequency in the step, plus the last one. PrePoMax opens it at the last moment. Step back through the others with the increment controls, or animate them. The first frame PrePoMax offers, increment 0, is its own empty placeholder; the solution starts at increment 1.

What the cloud solves

Heat conduction, with temperature as the one field:

  • Steady state or transient, one step per analysis.
  • Loads and boundaries: prescribed temperatures, surface heat flux, volumetric heat sources (a source may follow an amplitude curve over time), concentrated heat on structured meshes, and convection with a film coefficient and sink temperature. Faces you leave unset stay insulated, as in CalculiX.
  • Geometry: 3D solids, plane 2D and axisymmetric models. A structured box mesh is solved exactly on that grid. Other meshes (tetrahedra, wedges, distorted bricks, triangles) are sampled onto a regular grid, which approximates curved and sloping surfaces to first order; every such run says so in a warning.
  • Two nonlinear cases, steady state only: radiation to the environment at a fixed sink temperature, and conductivity that depends on temperature. Both are solved as a short series of linear cloud solves until the temperatures stop changing, and the monitor shows each pass.

A model meshed with tetrahedra comes back on the grid the cloud solved on, and PrePoMax shows those grid cells. On the tube below, the round bore became a stepped opening. The temperatures along the tube are right; near curved and sloping surfaces they are a first-order approximation of your geometry. When that matters, point PrePoMax back at CalculiX for that model, as in step 4.

Out of scope, so these run on your own CalculiX: structural, modal, buckling and dynamic analyses, coupled thermal-structural analyses, cavity radiation with view factors, contact, tied surfaces and gap conductance, density or specific heat that depend on temperature, anisotropic conductivity, box meshes with uneven spacing, analyses with more than one step, and films, radiation or prescribed temperatures that change during a transient step.

Two more cases are refused on purpose, both on meshes sampled onto a grid: a prescribed surface the grid would never touch, and a material layer thinner than one grid cell. Sampling would change the problem itself there, so these run locally too.

To check a particular model, run it: if the cloud doesn't take it, the monitor names every keyword that kept it out.

While it solves, and after

The monitor shows progress as the job runs, and PrePoMax stays yours meanwhile.

Kill in PrePoMax stops the waiting; the job keeps running in the cloud, and no local run starts. Run the same analysis again and the solver picks up that job instead of submitting a new one. If you changed the model in between, the solver cancels the old job, solves the new model and notes this in the monitor.

Your model and your data

The solver reads the analysis on your machine and sends only the problem it describes: the grid, materials, loads and boundary conditions. Your .pmx, the .inp PrePoMax writes and the other files in its work directory are not sent. The problem is solved on the machines of the group or project you chose, and the result comes back into PrePoMax's work directory.

Sign-in happens in your browser, and the session is stored encrypted in your Windows profile.

If something goes wrong

Open Doctor in the solver window. It checks the configuration, the local CalculiX, the server, your sign-in and your compute target, and each check that fails names the fix.

  • The monitor shows CalculiX's banner and no omnibuscloud-solver line at the top. PrePoMax's Executable still points at CalculiX. Repeat step 4.
  • The monitor says you're not signed in. The session has ended, and the analysis runs locally. Sign in again from the Start menu.
  • The network is down. The solver waits about five seconds for the server, says it didn't answer, and runs the analysis locally.
  • The chosen group or project is no longer available to you. The monitor lists what is, and the analysis runs locally. Pick another one under Compute target.

For scripted and automated setups, Configuration → Require cloud turns every local fallback into an error. For everyday work, leave it off.

About opens the solver's log folder, which is what to send if you ask for help.

What's next

Questions, or a model the solver refused that you think it should take? Ask in r/OmnibusCloud →. We read everything.

Let's build the ultracomputer together!