ADDA is a C software package (console application) to calculate scattering and absorption of electromagnetic waves by particles of arbitrary shape and composition using the discrete dipole approximation (DDA). The particles can be located in a homogeneous medium or near a plane substrate; emission (decay-rate) enhancement of point emitters can also be calculated. The main feature of ADDA is the ability to run on a multiprocessor system or multicore processors (parallelizing a single DDA simulation). It can also employ modern GPUs to accelerate computations. ADDA is intended to be a versatile tool, suitable for a wide variety of applications ranging from interstellar dust and atmospheric aerosols to metallic nanoparticles and biological cells. Its applicability is limited only by available computer resources.

ADDA originated at the University of Amsterdam but has then evolved into an open-source international project.

ADDA is an open-source parallel implementation of the discrete dipole approximation, capable to simulate light scattering by particles of arbitrary shape and composition in a wide range of particle sizes. The following list of features corresponds to the latest stable version.

• Parallel implementation
• Arbitrary particle shape and composition
• Full control over scattering geometry/environment
• A wide variety of calculated quantities
• Fast and accurate
• Easy to use
• Reliable
• Actively developed