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14 fast mouse

It is time for a new computer! What should I get?

We are often asked for computer hardware recommendations to reduce the time required to solve a GRTMPS planning case. Let's answer the hardware question and throw in some additional suggestions that can reduce run times.

When Running Single Cases

When solving GRTMPS planning cases one at a time (without MultiCore), these suggestions will reduce runtime.

Hardware
For single planning cases, it is all about the CPU. Specifically, the speed of individual cores. Exception: if your models uses a lot of mixed integer programming variables (MIP), more cores will help.

4GB of physical RAM is sufficient for almost any situation and hard disk speed is seldom important.

Software

  • Windows versions do not matter much.
  • When using PSI -1, the Excel version matters but PSI-2 is the better way to go. More on that later.
  • GRTMPS. The development team is always enhancing the program to run faster and the difference can be dramatic. When possible, update to the latest version.

GRTMPS MultiCore

MultiCore is an inexpensive upgrade to GRTMPS that will allow your computer to solve multiple planning cases simultaneously. GRTMPS MultiCore will run on any Windows computer and carefully enhancing hardware can make a big performance difference when solving multiple jobs.

When solving many cases simultaneously with MultiCore, all of the hardware elements are important. The suggestions below are for personal laptops and desktops.

CPU
More CPU cores is the key to maximizing the number of jobs solved in the minimum time. For most of us that means an Intel i7 (usually four physical cores, eight virtual cores). Once you have lots of cores, selecting a CPU with a newer architecture and faster clock rates is a bonus.

Storage
Traditional hard disks are easily overwhelmed when solving multiple jobs. You want a solid state drive (SSD) to keep up with your busy CPU.

RAM
How much is enough? With an Intel i7 (8 virtual cores), it would be rare that anyone would need more than 16GB.

Excel and PSI-1
When solving simultaneous cases, Excel's impact on runtime becomes critical and, potentially, disasterous. Keep reading.

Excel, PSI-1 and PSI-2

GRTMPS Process Simulator Interface, PSI, is a brilliant modeling technique that enables you to model non-linear behavior (usually process units but also blending) external to the normal GRTMPS data; within an Excel spreadsheet. Because the modeling work is done within good 'ol Excel, you are working with your favorite cell equations and the ability to link to other data sources. The result, the modeler is using a familiar and powerful tool to model complex units (e.g., FCC, reformer, etc) and blends (e.g., ethanol). The steps to implement PSI are easy though good modeling technique is, as always, important. Because it is based on adherent recursion technology, PSI is fast and convergent. Contact GRTMPS support for advice on PSI best practice.

Let's talk about Excel. We all love Excel but it's calculation engine is a poor perfomer especially when running concurrently with other instances of Excel. Increasing the number of Excel instances will cause small amounts of slowdown until a critical level is reached and the slowdown becomes dramatic and disasterous. It doesn't completely crash but you will think it has because runtimes are increased by orders of magnitude. Very bad news.

Enter PSI-2. You enjoy the same, wonderful Excel working environment to develop the PSI worksheets. But, when the planning case is run, Haverly's proprietary calculation engine replaces Excel. The result, a big speed improvement and no concurrency problems.

The best news is that converting to PSI-2 is, in most cases, easy and accomplished in minutes. For more information see technote HTN-1504, Process Simultaor Interface (PSI-2) published 3 September, 2015.

In summary, whether you are running one job at a time or using MultiCore to power through many jobs, PSI-2 is faster and better.

Many speed-up opportunities do not require a new computer

Model Health ...the biggest bang for your buck
Usually more than hardware or anything else, the biggest impact on runtime is the number of recursion passes. Paying attention to convergence, minimizing the number of passes, is the key to reducing runtime. Improving convergence is all about good modeling and this is a topic for another blog article or an entire course. Contact GRTMPS support for ideas. Consider using your pre-paid support days for Haverly to perform a model audit.

Windows 64-bit and your Optimizer
Depending on your model, 64-bit optimizers can be faster than 32-bit optimizers. If your computer is running a 64-bit version of Windows, the newer versions of GRTMPS will automatically run the 64-bit version of H/Cplex or H/Xpress.

Anti-Virus Software
AV software is a necessary evil that slows down processing. By adding your GRTMPS working directories to the AV software exclusion list, you can avoid much of that overhead when solving a planning case. When the correct and complete information is provided, we do not know of an I.T. department that has rejected adding GRTMPS working directories to the AV exclusion list. If you need more information, contact GRTMPS tech support.

File Location
All files should be stored on the local drive. Accessing files on a file server will increase running time dramatically.

Output
Are you creating reports or other output files you don't use? Turn off what you do not need.

Conclusion

Many speed-up opportunities do not require a new computer: good modeling, anti-virus exclusions, switching to PSI-2.  See also Effective Use of Spooling.

Good performance with MultiCore requires a computer with a good balance between the hardware elements without any weak links; a good balance between CPU, file storage and RAM.

From Randy's Desk 20th April 2017.

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