Is PLAXIS 3D enabled for multicore?

Yes, it is. In fact, a dual-core CPU is required for PLAXIS 3D. More than two cores are supported under the Geotechnical SELECT Entitlements [VIP] licence.

Input program

The PLAXIS 3D Input program can perform multicore operations: this is used amongst others during the intersection process (going from soil/structures mode to e.g. mesh mode), when loading large PLAXIS 3D projects, during rendering, etc.. Because of the availability of multicore, the whole user experience is a lot smoother for large PLAXIS 3D projects.

Calculation in PLAXIS 3D 2010: parallel independent phases

Although the PLAXIS 3D 2010 calculation kernel itself is optimised for a single-threaded calculation for each phase, the PLAXIS 3D 2010 program uses a smart routine to optimise the calculation time for the calculation of all phases: it can assign different calculation phases to separate cores. However, a depending phase can only be calculated if the previous is already calculated successfully. This means that when you have a single line of phases, multicore is not utilised. But if you have several phases starting from the same phase, they can all be calculated independently of each other. This is especially useful when calculating a safety analysis for several stages in your project, as these can be calculated next to the normal sequence of your staged construction phases. Depending on your project and the number of cores and the available memory this can speed up your calculation quite a lot.

Calculation in PLAXIS 3D 2011 and later: multicore calculations

Since the release of PLAXIS 3D 2011, the user may choose different solver types to solve the matrix equations:

• Picos (multicore iterative). It stands for Plaxis Iterative Concurrent Solver library. Picos is an efficient iterative solver that solves the system of equations in parallel on multi-core processors. It is generally the fastest way to perform calculations.
• Pardiso (multicore direct). It stands for Parallel Sparse Direct Solver. Pardiso is a direct solver that solves the system of equations in parallel on multi-core processors. It is generally the most robust way to solve equations, but it has also the highest memory consumption.
• Classic (single core iterative). This is the iterative solver that has been used in the previous PLAXIS 3D version: PLAXIS 3D2010. It solves the system of equations using only a single core on the processor.

For more information about these solvers, please refer to the Reference Manual.

The user may also set the Max cores to use. This number specifies how many cores will be used per phase calculation. If the number is larger than the number of available cores in your computer, the calculation will only use the available physical cores. E.g. on a quad core PC using the default 256 Max cores to use, you will use 4 cores for the phase calculation in a multi-core calculation (Picos or Pardiso solver).
Note that the calculation will only start a phase calculation when there are enough CPU cores available to launch a phase calculation.

Depending on the setup of the calculation, the following may happen:

• maximum number of cores: one phase at the time. When the number of maximum cores to be used for a phase is set to a number equal or greater than the number of available CPU cores, it will use the maximum number of cores per phase, leaving no room for any additional calculation to be run at the same time.
• 1 core per phase: independent phase calculation. When you limit the number of cores per phase to one [1] or you use the Classical solver, you will get the same behaviour as in PLAXIS 3D 2010: a single core calculation, but with the possibility of calculating independent phases at the same time.
• assuming you are working on a quad (4) core computer, and you limit all your phases to only use 2 cores, each phase on itself will do a dual core parallel calculation, while the computer is capable of handling a maximum of 2 independent phases at the same time.
• assuming you are working on an OctaCore (8) core computer, and you limit all your phases to only use 2 cores, each phase on itself will do a dual core parallel calculation, while the computer is capable of handling a maximum of 4 independent phases at the same time.
• assuming you are working on an OctaCore (8) core computer, and you limit all your phases to only use 3 cores, each phase on itself will do a 3 core parallel calculation, while the computer is capable of handling a maximum of 2 independent phases at the same time, leaving 2 cores free for other programs.
• assuming you are working on a quad (4) core computer, and you limit all your phases to only use 3 cores, each phase on itself will do a 3 core parallel calculation, while the computer is not capable of handling independent phases calculation at the same time, but it will leave 1 core free for other programs on your system.

Without a VIP licence, the number of used cores during the calculation is limited to two cores.

Trouble shooting

• PLAXIS 3D2011: In some cases when using the Picos solver with multiple cores to calculate a phase, and slow convergence is encountered, it could help to switch to use 1 CPU, or use the Pardiso solver or Classic solver
• PLAXIS 3D2011.00: The Pardiso solver is limited to 100,000 elements. When there is not enough memory available to use the Pardiso solver, or this element limit has been reached, it will switch to the Picos solver
• in PLAXIS 3D2011.01: The Pardiso solver's limit is now raised to 200,000 elements. When there is not enough memory available to use the Pardiso solver, or this element limit has been reached, it will switch to the Picos solver.
• since PLAXIS 3D 2013, the Pardiso solver's limit has been raised to a maximum of 300,000 elements. When there is not enough memory available to use the Pardiso solver, or this element limit has been reached, it will switch to the Picos solver.
• since PLAXIS 3D AE, the Pardiso solver's limit has been raised to a maximum of 500,000 (active) elements. When there is not enough memory available to use the Pardiso solver, or this element limit has been reached, it will switch to the Picos solver.