The big error you made originally is calling collect in every iteration of
the loop. Just deleting collect speeds things up by 100x. The lesson is
that you should (almost) never use collect.
The other lesson is: don't do [1:0.1:10]. It makes your code slower, and
very soon your it will stop working correctly. Just delete [].
function mindist0(x, val)
# your original
min_i = 0
min_x = 1.0
for i=1:length(x)
e = abs(collect(x)[i] - val)
if e < min_x
min_x = e
min_i = i
end
end
return (min_i, min_x)
end
function mindist1(x, val)
# same as the original, except removing 'collect'
min_i = 0
min_x = 1.0
for i = 1:length(x)
e = abs(x[i] - val)
if e < min_x
min_x = e
min_i = i
end
end
return (min_i, min_x)
end
function mindist2(x, val)
# using enumerate to avoid indexing
min_i = 0
min_x = Inf
for (i, xi) in enumerate(x)
dist = abs(xi - val)
if dist < min_x
min_x = dist
min_i = i
end
end
return (min_i, min_x)
end
function test_dist(x, val, N)
# putting time testing inside a function for optimal result
@assert mindist0(x, val) == mindist1(x, val) == mindist2(x, val)
@time for _ in 1:N mindist0(x, val) end
@time for _ in 1:N mindist1(x, val) end
@time for _ in 1:N mindist2(x, val) end
end
>> test_dist(1:0.1:10, 8.22, 1)
0.000060 seconds (182 allocations: 76.781 KB)
0.000001 seconds
0.000001 seconds
>> test_dist(1:0.1:10, 8.22, 1)
0.641741 seconds (1.82 M allocations: 749.817 MB, 7.57% gc time)
0.007380 seconds
0.005570 seconds
