Could someone help me to understand why the following code works slowly and
how to make it run faster?
function run()
# this is fast
s1 = string("x = [0", join([string(", ", i) for i in 1:256]), "]")
p1 = parse(s1)
@time eval(p1)
@time eval(p1)
# here starts the slow part
s2 = string("x = ['0'", join([string(", ", i) for i in 1:128]), "]")
p2 = parse(s2)
@time eval(p2)
@time eval(p2)
s3 = string("x = ['0'", join([string(", ", i) for i in 1:256]), "]")
p3 = parse(s3)
@time eval(p3)
@time eval(p3)
s4 = string("x = ['0'", join([string(", ", i) for i in 1:192]), "]")
p4 = parse(s4)
@time eval(p4)
@time eval(p4)
println("done")
end
run()
I understand that arrays of Any would evaluate slower than arrays of
specified type but there seems to be a qualitative difference in how they
are handled. It seems that the problem is with compilation of the code as
after we run eval(p3) then consecutive run is fast and eval(p4) is also
fast.
The comparable code in Python:
exec("x = [0"+"".join([", " + str(i) for i in range(1, 513)]) + "]")
exec("x = ['0'"+"".join([", " + str(i) for i in range(1, 513)]) + "]")
runs fast in both cases.
The problem here is an artificial example. The actual situation occurred
when I was trying to include code that constructed a long vector of strings
consisting of ASCIIString and UTF8String entries (some of the string
literals included code contained only ASCII characters and some did not eg. x
= ["a", "ą"], the actual vector was much longer).
Thank you,
Bogumił
