# Difference between revisions of "MEEP"

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Meep (or MEEP) is a free finite-difference time-domain [1] simulation software package developed at MIT to model electromagnetic systems. A number of people, including @aero, have been using it to simulate the evolution of the fields within the EM Drive.

# Linux Setup

Details regarding setting up Meep for EM Drive simulations on Linux are provided below.

@leomillert recommended[2] the following:

• Meep 1.3 (compiled & installed from its sources[3])
• libctl 3.2.2 (compiled & installed from its sources)
• Guile 2.0.11 (id)
• Harminv 1.4 (id)
• OpenBLAS 0.2.12 (installed from its binaries)
• HDF5 1.9.224 (compiled & installed from its sources)
• h5utils 1.12.1

The installation for a single machine is described here. Parallel/cluster installs are documented here

# Usage

The instructions below were provided by @leomillert:[4]

1. Execute

wget https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=37642.0;attach=1042821 -O NSF-1701.ctl
meep NSF-1701.ctl


After completion of the execution, Meep outputs nine .h5 files. This may take a long time depending on your computer.

2. Create CSV files

h5totxt -t 13 -0 -y -0  ex.h5 > zCopper-exy.csv


3. Open zCopper-exy.csv in a spreadsheet and aero's zCopper-exy.csv (TBD:provide location of aero csv) on another. Open a third spreadsheet that is one spreadsheet values minus the other, entry by entry. Check the highest entry (in absolute value) of the difference. If it's negligible you are good to go. If it's a value too big (greater than 10^-6), your Meep installation isn't in sync with ours, so it's of no use.

4. Now you are good to go. Make a new directory to start the tests. Copy NSF-1701.ctl there.

5. Open NSF-1701.ctl in a text editor and change a single value. For example, (set! high 10.2) means the model is 10.2 inches high. Change the 10.2 to another value and save NSF-1701.ctl with this single change. This is called sensitivity analysis. One value at a time. (set! high 10.2) was just an example, change any value of interest

meep NSF-1701.ctl
h5totxt -t 13 -0 -y -0  ex.h5 > zCopper-exy.csv


6. Compare your new zCopper-exy.csv with your old one. See if there was any relevant change (do the spreadsheet comparison again). If there was no considerable change in values, it means the modification made doesn't impact the behavior of the EMDrive. This is an important information for scientists, so let us know. Otherwise, if there was a significant change, let us know if it was positive or negative and its intensity. If you don't know how, just upload the .h5 files somewhere and we will analyze it.

# Amazon EC2 AMI

A public AMI with meep installed has been made available (by @dumbo). The AMI name is ubuntu-trusty-meep-emdrive and the AMI ID is ami-3f54560f. Due to the long computing times required to simulate the frustum until "saturation" (for lack of a better term), some people may find it more convenient to run the simulation on EC2 than on their local workstation.

The AMI is based on Ubuntu (Trusty) with packages meep and meep-mpi-default installed.

# Models & results

TBD: Add reference to all existing models and associated results here, with a succinct description.