01: Hello, 42!

Let’s take a look at everything going on in the “Hello, 42!” example program.

local L = require 'ebblib'

In addition to importing the language, we probably also want to require Ebb’s standard library. require is the standard Lua mechanism for pulling in modules, similar to C’s #include, or Java/Python’s import.

local GridLibrary = require 'ebb.domains.grid'

In addition to the Ebb standard library, we usually require some number of other support libraries. In particular, we’ll usually want to require at least one geometric domain library. Ebb provides a set of default domain libraries available at ‘ebb.domains.xxxx’; Here we use the grid library.

local GridLibrary = require 'ebb.domains.grid'

After importing Ebb, we usually require some number of support libraries. In particular, we’ll usually want to require at least one geometric domain library. Ebb provides a set of default domain libraries available at 'ebb.domains.xxxx'; Here we use the grid library.

local grid = GridLibrary.NewGrid2d {
  size          = {2,2},
  origin        = {0,0},
  width         = {2,2},
}

Using the grid library, we can create a new domain. Here we’re telling the library that we want a 2x2 (size) 2d grid, with its origin at (0,0) and with grid width 2 in each dimension.

local ebb printsum( c : grid.cells )
  L.print(21 + 21)
end

After creating a domain, we define computations over that domain using Ebb functions. Here, we define a function printsum which takes a cell of the grid as its argument. We sometimes call functions that take domain elements as their only argument kernels. These kernels represent data parallel computations over the geometric domain.

grid.cells:foreach(printsum)

Finally, we invoke this function for each cell in the grid. Since there are 4 cells, this will print out the sum 4 times.