I recall that with earlier versions of PVsyst, the "Computes the integrals for diffuse" step was only necessary for the initial simulation run of a variant, so long as no changes were made to the shading scene or orientation settings.
With PVsyst 8.0.6 I'm finding that this step is repeated with every simulation run, even with *no changes in settings*.
Please let me know if there's something that I'm missing. For some of my models with complex shading scenes, each simulation is taking several hours to complete.