hi,

i have a vellum cloth setup, nothing special a simple dress (made with marvelous and remeshed for houdini), about 10K prims, so fairly low-poly.
vellum solver settings are mostly default, time step 4, 250 constraint iter...
when i simulate, it takes about 1.2 sec per frame, which leads on a 200frames simu in about 4-5min simulation time and the simu i consider not final, since it flickers when it comes to rest, so settings should be raised up...

nevertheless, when i simulate in marvelous, the dress then contains about 50K prims and it simulates (in cpu mode) in about 30secs, no flicker and it looks awesome...simulation settings fairly high (for animation)...

i am wondering why vellum solver is sooo slow (opencl is enabled in the solver)...and how can be it improved? somethin in the solver settings that has to be enabled to make it faster?
i would like to simulate in houdini, since it has more flexibility on settings things up or art direct the cloth...but the simulation speed is sooo slow, comparing to marvelous designer...

Marvelous Designer is simply more optimized when it comes to cloth simulation. Vellum, being a XPBD solver, is not, and will not be the fastest cloth solver.

Very generally speaking, Houdini's built-in solvers are not the best on the market for a specific job. Houdini is the most versatile one tho. Think about it, MD is about as expensive as Houdini, but it can only do cloths. If Vellum cloth is as good as MD, then what's left for MD? Bankruptcy.