Why is this code allocating?

General Usage Performance
,
1

Why is the following code allocating:

using VortexStepMethod

# Step 1: Define wing parameters
n_panels = 20          # Number of panels
span = 20.0            # Wing span [m]
chord = 1.0            # Chord length [m]
v_a = 20.0             # Magnitude of inflow velocity [m/s]
density = 1.225        # Air density [kg/m³]
alpha_deg = 30.0       # Angle of attack [degrees]
alpha = deg2rad(alpha_deg)

# Step 2: Create wing geometry with linear panel distribution
wing = Wing(n_panels, spanwise_panel_distribution=LINEAR)

# Add wing sections - defining only tip sections with inviscid airfoil model
add_section!(wing, 
    [0.0, span/2, 0.0],    # Left tip LE 
    [chord, span/2, 0.0],  # Left tip TE
    INVISCID)
add_section!(wing, 
    [0.0, -span/2, 0.0],   # Right tip LE
    [chord, -span/2, 0.0], # Right tip TE
    INVISCID)

# Step 3: Initialize aerodynamics
body_aero::BodyAerodynamics = BodyAerodynamics([wing])

for panel in body_aero.panels end
@time for panel in body_aero.panels end

This gives me as output:

julia> @time for panel in body_aero.panels end
  0.000012 seconds (20 allocations: 640 bytes)

It is the second execution of the same line of code, which is for panel in body_aero.panels end. So I am not doing much, just iterating over all elements of a vector of Panel structs.

Iterating over a vector should not allocate, or what am I missing?

2

OK, found the answer: I need to put my code into a function to measure allocations:

function test(body_aero)
    for panel in body_aero.panels end
end

test(body_aero)
@allocated test(body_aero)

This doesn’t allocate.

2 Likes