[julia-users] Memory allocation in BLAS wrappers

[adokano]

I am writing a Julia function which implements some of the functionality of 
the LAPACK function TPQRT, but my version stops before computing the block 
reflectors. In my function, I make several calls to gemv! and ger! from 
Base.LinAlg.BLAS. Each of these calls seems to generate extra overhead of 
440 bytes according to the output of --track-allocation, and since each of 
those functions gets called several times within a function that also gets 
called many times, the extra allocations blow up and I end up spending a 
large chunk of time in garbage collection. Is it normal for each function 
call to dynamically allocate so much space? Here is the function in 
question:

function tpqrf!( A::StridedMatrix{Float64}, B::StridedMatrix{Float64}, 
                 tau::StridedVector{Float64}, work::Vector{Float64} )
  m,n = size(B)
  for j = 1:n
    # Construct Householder reflector
    A[j,j], tau[j] = larfg!(A[j,j], sub(B, :, j), tau[j])
    # Apply reflector to remainder
    for i = j+1:n
      work[i] = A[j,i]
    end
    Base.LinAlg.BLAS.gemv!('T', 1.0, sub(B,:,j+1:n), sub(B,:,j), 1.0, 
sub(work,j+1:n))
    for k = j+1:n
      A[j,k] = A[j,k] - tau[j]*work[k]
    end
    Base.LinAlg.BLAS.ger!(-tau[j], sub(B,:,j), sub(work,j+1:n), 
sub(B,:,j+1:n))
  end
end

Thanks,
Aaron