I did blas_set_num_threads(1) with the same profile numbers. This is using
Apple’s BLAS.
Maybe I’ll try 0.5 and OpenBLAS for comparison.
> On 10 Sep 2016, at 2:34 AM, Andreas Noack <andreasnoackjen...@gmail.com>
> wrote:
>
> Try to time it again with threading disabled. Sometimes the threading
> heuristics can cause unintuitive performance.
>
> On Friday, September 9, 2016 at 6:39:13 AM UTC-4, Sheehan Olver wrote:
>
> I have the following code that is part of a Householder routine, where
> j::Int64, N::Int64, R.cols::Vector{Int64}, wp::Ptr{Float64}, M::Int64,
> v::Ptr{Float64}:
>
> …
> for j=k:N
> v=r+(R.cols[j]+k-2)*sz
> dt=BLAS.dot(M,wp,1,v,1)
> BLAS.axpy!(M,-2*dt,wp,1,v,1)
> end
> …
>
>
>
> For some reason, the BLAS.dot call takes 3x as long as the BLAS.axpy! call.
> Is this expected, or is there something wrong?
>
>
