Amumax

fork of mumax3 meant to increase the integration with a python processing workflow. I made my own wrapper around zarr called pyzfn which leverages the mumax data in the zarr format.

The solvers ( and results ) are unchanged, this is just list of massive quality of life improvements making working with the output data much more efficient and convenient.

It's not 100% compatible with the original .mx3 files. See changes below.

Installation

Linux

Install script

Don't just run an script on the internet. Read it, check what it does and then you can run this command to install amumax:

sh -c "$(curl -fsSL https://raw.githubusercontent.com/MathieuMoalic/amumax/main/install.sh)"

Manually

Download cufft and curand, unpack and add the shared objects to $PATH, or just install the full CUDA suite with your package manager. Download the latest release:

curl -L https://github.com/mathieumoalic/amumax/releases/latest/download/amumax > amumax
amumax -v

libcurand.so and libcufft.so must either be in the same folder as amumax or on $PATH.

Windows

• Get linux: https://learn.microsoft.com/en-us/windows/wsl/install
• Follow the steps above.

Differences from mumax3

New way to define the mesh

Tx,Ty,Tz,Nx,Ny,Nz,dx,dy,dz,PBCx,PBCy,PBCz are now predefined variables. You define the Mesh through them. You don't need to call a function to initiate the Mesh, it is automatically done the first time you run a solver but you can't redefine the Mesh after that ! Tx is the total size along the x axis. Nx is the number of cells along the x axis. dx is the number of cells along the x axis. Keep in mind that variables in mx3 script files aren't case sensitive so tx is like Tx for example.

old:

SetGridSize(256,256,10)
SetCellSize(1e-9,1e-9,1e-9)
SetPBC(32,32,0)

new:

Nx = 256
Ny = 256
Nz = 10
dx = 1e-9
dy = 1e-9
dz = 1e-9
PBCx = 32 // Optionnal
PBcy = 32 // Optionnal
PBCz = 0 // Optionnal

new (alternative but equivalent):

Nx = 256
Ny = 256
Nz = 10
Tx = 256e-9
Ty = 256e-9
Tz = 10e-9
PBCx = 32 // Optionnal
PBcy = 32 // Optionnal

Variables that you define are automatically saved:

lattice_constant := 500e-9
ref_paper := "X et al. (2023)"

You can access it in the file .zattrs. Or using pyzfn:

print(job.lattice_constant)
print(job.ref_paper)

You can save data by chunks

Nx = 16
Ny = 32
Nz = 10
Tx = 16e-9
Ty = 32e-9
Tz = 10e-9
SetGeom(Universe())
sampling_interval = 5e-12
AutoSaveAsChunk(m,"m_chunked", sampling_interval, Chunk(1, 1, Nz, 3))
Run(1e-9)

This code will save the magnetization as chunks:

• The x and y dimensions are unchunked ( set as 1 in Chunk() )
• The z dimension will have as many chunks as cells across the thickness ( 10 in this case )
• mz, my and mz will be also chunked, saved separately. Why would you want it? Because it makes loading the data from disk MUCH faster if you chunk in a smart way. Say you want to calculate the FFT of the top layer of the y component of the magnetization, in this case, loading the data from disk will be around 30 times faster.

Other changes

• Remove the Google trackers in the GUI.
• Add saving as zarr
• Rename the functions to save .ovf files as SaveOvf and SaveOvfAs. You cannot autosave ovf files anymore.
• Add progress bar for run, can be turned off with -magnets=false
• Reorder GUI elements
• Dark mode GUI
• Check and warns the user for unoptimized mesh
• AutoMeshx = True,AutoMeshy = Trueand AutoMeshz = True will optimize the corresponding mesh axis for you (this function slightly changes the size and number of cells while keeping the total size of the system constant)
• Add chunking support as per the zarr documentation with the functions:
  • SaveAsChunk(q Quantity, name string, rchunks RequestedChunking)
  • AutoSaveAsChunk(q Quantity, name string, period float64, rchunks RequestedChunking)
• Chunk(x, y, z, c int) -> RequestedChunking chunks must fit an integer number of times along the axes. The chunks will be modified to be valid and as closed as the chunks you requested
• Add the ShapeFromRegion function
• Add new shapes : squircle, triangle, rtriangle, diamond and hexagon
• Add the AutoSaveAs function
• Add the Round function from the math library
• Add metadata saving : root_path, start_time, dx, dy, dz, Nx, Ny, Nz, Tx, Ty, Tz, StartTime, EndTime, TotalTime, PBC, Gpu, Host
• Add MinimizeMaxSteps and MinimizeMaxTimeSeconds to timeout long Minimize() runs.
• Everytime the function Save is used (from AutoSave for example), the current simulation time t is saved too as a zarray attribute
• Save compressed arrays (zstd) by default
• ext_makegrains now also takes a new argument minRegion. ext_makegrains(grainsize, minRegion, maxRegion, seed)
• Add colors for terminal logs

Building from source

Using nix:

nix run .#git

Using podman or docker:

git clone https://github.com/MathieuMoalic/amumax
cd amumax
podman run --rm -v $PWD:/src docker.io/oven/bun:1.1.27 bash -c "cd /src/frontend && bun run build && mv /src/frontend/dist /src/api/static"
podman build -t matmoa/amumax:build .
podman run --rm -v $PWD:/src matmoa/amumax:build
./build/amumax -v

The amumax binary and cuda libraries are then found in build.

Manually

You need to install git, bun, go, cuda. Then

git clone https://github.com/MathieuMoalic/amumax
cd frontend
bun install
bun run build
cd ..
mv frontend/dist api/static
export CGO_LDFLAGS="-lcufft -lcuda -lcurand -L/usr/local/cuda/lib64/stubs/ -Wl,-rpath -Wl,\$ORIGIN" 
export CGO_CFLAGS_ALLOW='(-fno-schedule-insns|-malign-double|-ffast-math)'
go build -v .

Contribution

I'm happy to consider any feature request. Don't hesitate to submit issues or PRs.

TODO

• Calculate the mesh when enough arguments are given instead of when SetGeom is called