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improve performance for sorting columns in sparse matrix (thereby improving sparse matmul) #29682

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Oct 19, 2018
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improve performance for sorting columns in sparse matrix (thereby improving sparse matmul) #29682

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40 changes: 25 additions & 15 deletions stdlib/SparseArrays/src/sparsematrix.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -3401,37 +3401,47 @@ function sortSparseMatrixCSC!(A::SparseMatrixCSC{Tv,Ti}; sortindices::Symbol = :
row = zeros(Ti, m)
val = zeros(Tv, m)

for i = 1:n
@inbounds col_start = colptr[i]
@inbounds col_end = (colptr[i+1] - 1)
perm = Base.Perm(Base.ord(isless, identity, false, Base.Order.Forward), row)

numrows = col_end - col_start + 1
@inbounds for i = 1:n
nzr = nzrange(A, i)
numrows = length(nzr)
if numrows <= 1
continue
elseif numrows == 2
f = col_start
f = first(nzr)
s = f+1
if rowval[f] > rowval[s]
@inbounds rowval[f], rowval[s] = rowval[s], rowval[f]
@inbounds nzval[f], nzval[s] = nzval[s], nzval[f]
rowval[f], rowval[s] = rowval[s], rowval[f]
nzval[f], nzval[s] = nzval[s], nzval[f]
end
continue
end
resize!(row, numrows)
resize!(index, numrows)

jj = 1
@simd for j = col_start:col_end
@inbounds row[jj] = rowval[j]
@inbounds val[jj] = nzval[j]
@simd for j = nzr
row[jj] = rowval[j]
val[jj] = nzval[j]
jj += 1
end

sortperm!(unsafe_wrap(Vector{Ti}, pointer(index), numrows),
unsafe_wrap(Vector{Ti}, pointer(row), numrows))
if numrows <= 16
alg = Base.Sort.InsertionSort
else
alg = Base.Sort.QuickSort
end

# Reset permutation
index .= 1:numrows

sort!(index, alg, perm)

jj = 1
@simd for j = col_start:col_end
@inbounds rowval[j] = row[index[jj]]
@inbounds nzval[j] = val[index[jj]]
@simd for j = nzr
rowval[j] = row[index[jj]]
nzval[j] = val[index[jj]]
jj += 1
end
end
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