Why does a function wait for a loop to finish before printing something inside the loop?

New to Julia
1

I have been using Julia since 0.4 and this is the first time that something like that happens. I have a function with a loop inside it and a print inside the loop. Usually I use this loop to know which parameters make the slower part of the calculation, but now, I do not get any output before the function finishes. This is with Julia 1.4. The function would be something like this:

function f(x)
aux=0
rr=0.001:0.001:x
for r in rr
print(r, " ")
aux+=somecomplicatedfun(r)
end
return aux
end

2

Probably because print is buffered. Try putting a flush(STDOUT) after the print.

1 Like
3

Okey, then my question becomes, why is

print

buffered now? In the other Julias this was not the case.

4

Printing was always and is asynchronous in julia. It may be caused by many things that, in new julia version, somecomplicatedfun® can run without task switch.

1 Like
5

Crossref to answer on Stackoverflow to avoid double work in answering: Julia waits for function to finish before printing message in a loop - Stack Overflow

1 Like
6

It would be nice if print / println had a keyword argument option to automatically flush, like for instance in Python

print(..., flush=True)
1 Like
7

I can also imagine a token that would flush, eg

struct Flush end
Base.print(io::IO, ::Flush) = flush(io)
const FLUSH = Flush()
print(..., FLUSH, other_stuff..., FLUSH)
3 Likes