FEA has a number of words and phrases that mean exactly the same thing.
Grid/Node: A point in space that defines the shape of elements. It is also where the solution is either found or set by an SPC/Constraint/Boundary Condition.
SPC/Constraint/Boundary Condition: A point at which the solution is set to a certain value. Examples include setting the displacement to zero at the end of a beam or setting the temperature to a certain value. Some solvers allow some panache when setting the solution to a certain value, such as in Abaqus, where one can use the uncommon architectural term 'encastre' to describe something that is fixed in place.
Degree of Freedom, DOF, detail level: how many numbers it takes to describe a complete solution. This is also a measure of how long it will take the model to solve.
Job/Model/Run/Input Deck: A data file, typically ASCII plain text, which fully describes the FEA problem which the solver will find a solution to. Sometimes a run can refer to the specific time a model was solved, in which case an analyst might describe the runs they did with different settings to find the fastest solution times based on things like memory and cpu settings.
Node/System: A single computer, one that may be a part of a networked computer cluster. This computer will typically have more than one CPU and a single large bank of memory that can be accessed by any of the CPUs
Stiffness Matrix/System of Equations: the series of equations which describe the behavior of the FEA system, stored in matrix form, typically in a sparse symmetric storage format, most commonly one that assumes symmetric matrices. A solver will work best if these matrices can fit into memroy without using the hard disks of the computer.
CPU/core: A single independent central processing unit. Due to advances in shrinking chip sizes, a typically computer will typically have more than one core, packaged together, which appears to the computer no different than several independent CPUs. High performance server computers may have more than one CPU slot, each with more than one core, for total CPU/core counts of 2x2 or more. CPU counts of 16 are not uncommon.
RAM/Memory/Random Access Memory: Memory in a computer which is fast but loses its state when the system is turned off. Typically measured in single digit to hundreds of gigabytes(GB).
Hard Disk/Hard Drive/SSD: Slow but permanent memory which does not lose its state when a computer is turned off. Although SSD's have narrowed the distance between traditional magnetic memory hard drives and RAM, SSDs and hard drives remain about 1,000 times slower.
SMP/Parallel: A style of solving a system of equations that applies more CPUs but little extra memory to the same problem. An analogy would be sorting a shuffled deck of cards on a table. An SMP/parallel approach would be to spread the cards out over one table but have more than one person working to sort the cards
DMP: A style of solving a system of equations that applies more CPUS and more memory, either all on one node/system or several systems. If done on a single system, it is analogous to sorting a shuffled deck of cards on a large table, where each person sorting the cards is working on their own assigned portion of the table. If done on more than one system, it is analogous to more than one table in more than one room, which can pass cards back and forth between rooms, but always slower than back and forth across a table.
GPU/GPGPU/OPENCL: Using the simple but numerous programmable cpus of a graphics card to do general purpose vectorized computing.
No comments:
Post a Comment