Theory
The two parts of a project
<name>.spsim: every setting, the CAD model and the boundary assignment. Save writes only this file, so saving is quick even when the results are large.<name>_files: the working folder. The mesh is generated and the solver runs directly in it, so results are on disk the moment they are computed, whether or not the project has been saved since. Queued runs, parameter sweeps and mesh studies of the project are also kept inside it.
Before the first save
A new project, a sample or a model loaded from a CAD file works in a temporary folder (the scratch folder, File > Settings). You can mesh and solve before saving. The first Save asks where to put the project and moves the working files beside the project file. When a project that was never saved is closed, its temporary folder is deleted after the question whether to save it.
Save As
Save As writes a new project file and copies the _files folder to the new place; you then work on the copy. The original project stays as it was.
Opening a project
The program uses the _files folder beside the project file and puts the saved settings over it. A project file received on its own opens with its settings only; its _files folder is created and filled again when you mesh and solve. A project file in a folder that cannot be written to (an e-mail attachment, a read-only share) opens in the scratch folder; use Save As to keep your work.
Unsaved setting changes
Closing a saved project without saving discards the setting changes made since the last save. Results already computed stay in _files.
Sending a project to someone
File > Archive project (with results) writes one self-contained project file with the results inside. It opens like any project file; on first opening its _files folder is created from it.
After a crash
The program keeps a recovery copy of the settings of a project with unsaved changes, every few minutes (File > Settings). At the next start it offers to open it with the working files it was using, or to discard it. A temporary folder that nothing refers to any more is deleted at start-up.
Valid range
Path length
Windows limits a file path to 260 characters, and the solver writes files up to about 140 characters below the _files folder. Save warns when the path of the _files folder is longer than 110 characters; choose a folder with a shorter path then.
Network and synchronised folders
A project saved on a network drive or in a folder synchronised to the cloud works, but the solver writes many files while it runs, which is slower there and makes the synchronisation busy. A local folder is recommended while a case is being solved.