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demo_timer

timing code with a real stopwatch object.

catalog/demo_timer.qu

`tic()`/`toc()` is one global stopwatch, so it cannot time two things at once. `timer()` gives you as many independent stopwatches as you like.

What it exercises

Results

printed
sum of sqrt(1..2e6) = 1885618790.1
took 0.0294 s

inner section : 0.0151 s
whole block   : 0.0251 s
inner was 60% of the block

counted work only: 0.0100 s
(the array setup in the middle was not counted)

The whole program

Runnable as it stands: qu run catalog/demo_timer.qu

# demo_timer.qu — timing code with a real stopwatch object.

#

# `tic()`/`toc()` is one global stopwatch, so it cannot time two things at

# once. `timer()` gives you as many independent stopwatches as you like.

#

# Exercises:

#   timer()      make a stopwatch (it starts STOPPED -- call start())

#   start/pause  control it

#   elapsed()    read it WITHOUT stopping it

#   t.start()    method spelling; `t.f()` is the same as `f(t)`


# --- one stopwatch, the simplest use ------------------------------------

t = timer(1)
t.start()

total = 0
for i = 1 to 2000000
    total = total + sqrt(i)
end for

print("sum of sqrt(1..2e6) = {total:.1f}")
print("took {t.elapsed():.4f} s")
print("")

# --- two at once, which tic()/toc() cannot do ---------------------------

# `whole` keeps running while `part` times a section inside it.

whole = timer(1)
part = timer(1)

whole.start()

for i = 1 to 1000000
    total = total + i
end for

part.start()                       # start a second clock mid-flight

for i = 1 to 1000000
    total = total + sin(i)
end for
part_time = part.elapsed()

whole_time = whole.elapsed()       # reading it does NOT stop it


print("inner section : {part_time:.4f} s")
print("whole block   : {whole_time:.4f} s")
print("inner was {100 * part_time / whole_time:.0f}% of the block")
print("")

# --- pause and resume ---------------------------------------------------

# Time only the parts you care about, skipping the setup in between.

work = timer(1)
work.start()
for i = 1 to 500000
    total = total + i
end for
work.pause()                       # clock frozen here


x = zeros(200000)                  # setup we do NOT want to count

for i = 0 to 199999
    x[i] = i * 0.5
end for

work.start()                       # resumes from where it paused

for i = 1 to 500000
    total = total + i
end for

print("counted work only: {work.elapsed():.4f} s")
print("(the array setup in the middle was not counted)")