feat: Add volume of grid cells

Add a function dV that calculates the volume of the individual grid
cells.

Project.toml

@@ -1,7 +1,7 @@
 name = "UltraDark"
 uuid = "1c8d022d-dfc0-4b41-80ab-3fc7e88cdfea"
 authors = ["Nathan Musoke <[email protected]>"]
-version = "0.4.0"
+version = "0.4.1"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"

src/UltraDark.jl

@@ -9,6 +9,7 @@ using FFTW
 
 export simulate
 export Grids, PencilGrids
+export dV
 export Config, SimulationConfig, constant_scale_factor, TimeStepOptions
 export OutputConfig
 export SummaryStatistics, SummaryStatisticsMeanMaxRms

src/grids.jl

@@ -271,3 +271,29 @@ function rk_norm(lengths, resols)
 
     (kx.^2 .+ ky.^2 .+ kz.^2).^0.5
 end
+
+"""
+    dV(grids)
+
+Calculate the volume of each grid cell
+
+# Examples
+
+```jldoctest
+julia> using UltraDark
+
+julia> box_length = 1.0;
+
+julia> resol = 16;
+
+julia> g = Grids(box_length, resol);
+
+julia> dV(g) * resol^3 == box_length^3
+true
+
+```
+
+"""
+function dV(grids)
+    diff(grids.x, dims=1)[1] * diff(grids.y, dims=2)[1] * diff(grids.z, dims=3)[1]
+end

test/grids.jl

@@ -14,12 +14,16 @@ for grids_type in [Grids, PencilGrids]
         @test reshape(grids.x, resol) == reshape(grids.y, resol)
         @test reshape(grids.x, resol) == reshape(grids.z, resol)
 
+        @test dV(grids) * resol^3 == 1.0^3
+
         grids = grids_type((1.0, 1.0, 1.0), (resol, resol, resol))
         @test typeof(grids) <: grids_type
         @test all(grids.ψx .== 0)
         @test reshape(grids.x, resol) == reshape(grids.y, resol)
         @test reshape(grids.x, resol) == reshape(grids.z, resol)
 
+        @test dV(grids) * resol^3 == 1.0^3
+
         grids = grids_type((4.0, 2.0, 1.0), (4resol, 2resol, 1resol))
         @test typeof(grids) <: grids_type
         @test all(grids.ψx .== 0)
@@ -28,6 +32,8 @@ for grids_type in [Grids, PencilGrids]
         @test size(grids.z) == (1, 1, 1resol)
         @test reshape(grids.x, 4resol)[1 + 4resol÷2 - 4resol÷8:4resol÷2 + 4resol÷8] == reshape(grids.z, resol)
         @test reshape(grids.y, 2resol)[1 + 2resol÷2 - 2resol÷4:2resol÷2 + 2resol÷4] == reshape(grids.z, resol)
+
+        @test dV(grids) * 4resol * 2resol * 1resol == 4.0 * 2.0 * 1.0
     end
 end