Parallel processing Julia中的多线程问题
我正在尝试并行化一些代码位,但我不明白为什么以下函数main1()和main2()使用Julia的多线程给出不同的结果:Parallel processing Julia中的多线程问题,parallel-processing,julia,Parallel Processing,Julia,我正在尝试并行化一些代码位,但我不明白为什么以下函数main1()和main2()使用Julia的多线程给出不同的结果: a = rand(4,4);b = rand(4,4);c = rand(4,4);d = rand(4,4) function main1(a,b,c,d) L = zeros(2,2,16) FF = zeros(2,2,16) FT = zeros(2,2,16) F = Array{Float32}(undef,2,2) #
a = rand(4,4);b = rand(4,4);c = rand(4,4);d = rand(4,4)
function main1(a,b,c,d)
L = zeros(2,2,16)
FF = zeros(2,2,16)
FT = zeros(2,2,16)
F = Array{Float32}(undef,2,2)
# L = Array{Array{Float32, 1}, 4}
for i = 1:4
for j = 1:4
ic = i + j*(i-1)
F[1,1] = a[i,j]
F[1,2] = b[i,j]
F[2,1] = c[i,j]
F[2,2] = d[i,j]
L[:,:,ic] .= F * F'
FF[:,:,ic] .= F
FT[:,:,ic] .= F'
end
end
return L,FF,FT
end
function main2(a,b,c,d)
L = zeros(2,2,16)
FF = zeros(2,2,16)
FT = zeros(2,2,16)
F = Array{Float32}(undef,2,2)
# L = Array{Array{Float32, 1}, 4}
Threads.@threads for i = 1:4
Threads.@threads for j = 1:4
ic = i + j*(i-1)
F[1,1] = a[i,j]
F[1,2] = b[i,j]
F[2,1] = c[i,j]
F[2,2] = d[i,j]
L[:,:,ic] .= F * F'
FF[:,:,ic] .= F
FT[:,:,ic] .= F'
end
end
return L,FF,FT
end
如何正确修复main1()的并行化?您不能嵌套
@线程
循环,因此通常您应该执行以下操作:
Threads.@threads for u in vec(CartesianIndices((4,4)))
i,j = u.I
# your code goes here
end
但是,在代码中,对于(i,j)
的不同值对,您会得到相同的ic
值。在main1
中,您多次覆盖L
,FF
,FT
的相同部分,这是一个明显的错误。多线程将改变数据被覆盖的顺序,从而产生不同的结果。总之,首先修复main1,然后将其并行化