[julia-users] Segfault / Undefined reference

[Archibald Pontier]

Hi everyone,

Julia is (sometimes) segfaulting when running this function :

function emloop(img, Sigma, mu, t, model, imgc, bg, FullTs)
  EMiter = 1;
  Check = typemax(Float64);
GModels, Genes,
  (x, y) = size(img);
  D = zeros(x, y); E = zeros(x, y); B = zeros(x, y);

  # And we start the EM loop
  while EMiter <= maxEM && Check > ϵ
    # Calculate the betas & find the optimal transformation for the current 
iteration
    (D, E, B) = fastBetas(model, [], mu, Sigma, img);
    nt = findTransform(model, B, Gray((bg.r + bg.g + bg.b)/3), FullTs);

    # Now calculate the optimal parameters for the appearance model
    OldMu = mu;                  # For termination purposes
    (mu, Sigma) = calcTheta(img, D, E, B);

    # Apply the transformation found to the image
    img = RigidTransform(img, nt, bg, true, true);

    # Deal with the transformation
    Oldt = t;
    t += nt;
    t.tx %= x;
    t.ty %= y;

    # Termination criteria
    NormOldTT = sqrt((Oldt.tx - t.tx)^2 + (Oldt.ty - t.ty)^2 + (Oldt.θ - 
t.θ)^2);
    CheckMu = norm(OldMu.D - mu.D) + norm(OldMu.E - mu.E) + norm(OldMu.B - 
mu.B)
    Check = CheckMu + NormOldTT # Giving lots of weight to the 
transformation

    EMiter += 1;
  end

  return emdata(D, E, B, img, θ(Sigma, mu), t);
end

Some context: img is and Image{RGB{Float64}}, Sigma and mu are custom types 
:
type Σ
  D::Array{Float64, 2}
  E::Array{Float64, 2}
  B::Array{Float64, 2}
end

type μ
  D::Array{Float64, 1}
  E::Array{Float64, 1}
  B::Array{Float64, 1}
end

t is another custom type to represent a rigid body transformation 
(translation_x, translation_y, rotation_angle), bg is, for example, 
RGB(0.0, 0.0, 0.0) (black), and FullTs is an array of transformations, 
namely all the transformations we consider.

It's weird for multiple reasons: first of all, this code was running fine 
when not in a separate function returning a custom type (the custom type in 
the return is to ease the access since I want to call this function for an 
array of images with pmap and output all that which is not practical). 
Furthermore, sometimes it crashes with a segfault, sometimes with an 
undefined reference on this line, not always after the same EM iteration:
CheckMu = norm(OldMu.D - mu.D) + norm(OldMu.E - mu.E) + norm(OldMu.B - mu.B)

Thanks in advance for the help,
Archibald