# Tic() + toc/toq() VS @elapsed
**URL:** https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681
**Category:** New to Julia
**Created:** [January 25, 2017, 11:33am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681 "2017-01-25T11:33:41Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@chobbes](https://discourse.julialang.org/u/chobbes)
#### Post date: [January 25, 2017, 11:33am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/1 "2017-01-25T11:33:41Z")
Other than the difference in syntax, is there any essential difference between a combination of tic+toc and @elapsed? Any difference between what they return? The only difference described by the doc is as follows, which I don’t quite understand. Can anyone explain a bit?
> instead returning the number of seconds it (i.e. @elapsed) took to execute as a floating-point number.
Thanks a lot!!
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [January 25, 2017, 12:07pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/2 "2017-01-25T12:07:55Z")
The all use the same basic functionality (see `time_ns()`), but provide a different user interface. `@time` displays the time (and other info), use `@elapsed` when instead of displaying it, you would like to use the value, eg to compile statistics, etc, but see
> **[GitHub - JuliaCI/BenchmarkTools.jl: A benchmarking framework for the Julia...](https://github.com/JuliaCI/BenchmarkTools.jl)**
>
> A benchmarking framework for the Julia language. Contribute to JuliaCI/BenchmarkTools.jl development by creating an account on GitHub.
`tic` and `toc` save the info in the global state (of the task). I find `@time` and `@elapsed` cleaner, but YMMV. Also, it is very easy to implement a combination of `@elapsed` and `@time`, if for some reason you need both the time and the value (eg as a tuple).
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### Author:  [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)
#### Post date: [January 25, 2017, 2:43pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/3 "2017-01-25T14:43:09Z")
In addition to `@time`, as @Tamas_Papp mentioned, there is also `@timev`, which displays even more detailed information (about memory allocations, the GC, etc.), that can help if you are trying to figure out a performance issue.
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### Author:  [@chobbes](https://discourse.julialang.org/u/chobbes)
#### Post date: [January 25, 2017, 5:51pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/4 "2017-01-25T17:51:17Z")
> [@Tamas\_Papp](#):
>
> The all use the same basic functionality (see time\_ns()), but provide a different user interface… [redacted]
> [@ScottPJones](#):
>
> In addition to @time, as @Tamas_Papp mentioned, there is also @timev, which displays even more detailed information (about memory allocations, the GC, etc.), that can help if you are trying to figure out a performance issue.
Thanks both of you for the suggestions. Now I see the difference. I have been using BenchmarkTools.jl too to have more detailed statistics. However, if I want to use `@elapsed` or `@benchmark`, I have to wrap up all I want to time in a function. That’s not very convenient. That’s why I think I have to resort to using tic() and toc() sometimes.
May I know what most of you do when trying to time a few lines of your code in a big project or a large module? Do you also wrap the lines you want to time in a function in order to use `@elapsed` or `@benchmark`? Thanks!
---
### Author:  [@JeffreySarnoff](https://discourse.julialang.org/u/JeffreySarnoff)
#### Post date: [January 25, 2017, 6:05pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/5 "2017-01-25T18:05:50Z")
I use @benchmark to time a single call. BenchmarkTools is much more careful about compensating for externalities than are the other options.
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### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [January 25, 2017, 6:09pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/6 "2017-01-25T18:09:28Z")
You **do** want to wrap things in a function for [benchmarking](http://docs.julialang.org/en/latest/manual/performance-tips.html#Measure-performance-with-%5B@time%5D(@ref)-and-pay-attention-to-memory-allocation-1). But otherwise you could use
```julia
@time begin
...
end
```
---
### Author:  [@chobbes](https://discourse.julialang.org/u/chobbes)
#### Post date: [January 26, 2017, 10:57am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/7 "2017-01-26T10:57:27Z")
Thanks. For a standalone function without much of dependencies, I use `BenchmarkTools.jl` too. What do you use for timing a few lines of code in a project?
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### Author:  [@chobbes](https://discourse.julialang.org/u/chobbes)
#### Post date: [January 26, 2017, 11:00am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/8 "2017-01-26T11:00:00Z")
Thanks. This is very useful. One question - What is the breakdown of the time returned by `@time`? My understanding is the time returned by `@time` = compiling time + memory allocation time + computing time + GC time. Is it right?
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### Author:  [@dpsanders](https://discourse.julialang.org/u/dpsanders)
#### Post date: [January 26, 2017, 11:46am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/9 "2017-01-26T11:46:42Z")
_Never_ do this in global scope, though – the result is worse than meaningless. (I.e. it is actively misleading.)
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### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [January 26, 2017, 1:01pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/10 "2017-01-26T13:01:44Z")
I don’t think so. First, `@time` just _returns_ the result of evaluating the expression, not the elapsed time. That is displayed. At least on `0.5`, it _prints_ the elapsed time and the allocations (as a count, and the total memory allocated).
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### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [January 26, 2017, 1:06pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/11 "2017-01-26T13:06:18Z")
For quick & dirty timing I use `@time`, **twice** , wrapping things in a function. I only care about the second result. I do this realizing that there could easily be ±20% sampling errors.
For anything more serious, I use `BenchmarkTools.jl`. Which is a great tool. For very little time investment (learning how to use it), you get very nice & consistent benchmarks. For something quick, I use `seconds=3` to get three seconds worth of samples.
---
### Author:  [@chobbes](https://discourse.julialang.org/u/chobbes)
#### Post date: [January 26, 2017, 1:08pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/12 "2017-01-26T13:08:23Z")
> [@Tamas\_Papp](#):
>
> That is displayed.
What is displayed? Can you elaborate a bit?
> [@Tamas\_Papp](#):
>
> For quick & dirty timing I use @time, twice, wrapping things in a function. I only care about the second result. I do this realizing that there could easily be ±20% sampling errors.
>
> For anything more serious, I use BenchmarkTools.jl. Which is a great tool. For very little time investment (learning how to use it), you get very nice & consistent bench.marks. For something quick, I use seconds=3 to get three seconds worth of samples.
Thanks!! This is very helpful
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [January 26, 2017, 1:20pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/13 "2017-01-26T13:20:41Z")
> [@chobbes](#):
>
> What is displayed? Can you elaborate a bit?
The elapsed time (see second line below):
```julia
julia> x = @time 1+1
0.000007 seconds (4 allocations: 160 bytes)
2
julia> x
2
```
which also demonstrates that the value of `@time expr` is the value of `expr`.
---
### Author:  [@chobbes](https://discourse.julialang.org/u/chobbes)
#### Post date: [January 26, 2017, 1:24pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/14 "2017-01-26T13:24:37Z")
> [@Tamas\_Papp](#):
>
> which also demonstrates that the value of @time expr is the value of expr.
Thanks. Well. I thought you something else. Now I understand what you meant.
Can you give a breakdown of the value returned by @elapsed? I’m sorry. I’m really curious what may contribute to the total returned by @elapsed. Thanks!!
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [January 26, 2017, 1:41pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/15 "2017-01-26T13:41:49Z")
`@elapsed` just returns a single value, which, AFAIK, is wall time spent executing the expression (because `time_ns()` counts that). It is a very simple macro. You can read the source, eg using `@edit @elapsed 1` or something like that.
---
### Author:  [@JeffreySarnoff](https://discourse.julialang.org/u/JeffreySarnoff)
#### Post date: [January 26, 2017, 2:07pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/16 "2017-01-26T14:07:36Z")
```
using BenchmarkTools
macro nanosecs(xs...)
quote
bench = @benchmark $(esc(xs...))
t0 = bench.times[1]
t1 = median(bench.times)
tm = round(Int64, 2/(1/t0 + 1/t1))
return tm
end
end
macro memused(xs...)
quote
bench = @benchmark $(esc(xs...))
a = bench.allocs
m = bench.memory
return (m,a)
end
end
# use values held in variables
a = 0.75
@nanosecs sin(a)
# Int64 harmonic mean of fastest and median
@memused sin(a)
# total bytes, distinct allocations
```
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [January 26, 2017, 4:38pm UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/17 "2017-01-26T16:38:44Z")
> [@Tamas\_Papp](#):
>
> For anything more serious, I use BenchmarkTools.jl. Which is a great tool. For very little time investment (learning how to use it), you get very nice & consistent benchmarks. For something quick, I use seconds=3 to get three seconds worth of samples.
Note that BenchmarkTools now has `@btime` and `@belapsed`, which are drop-in replacements for `@time` and `@elapsed`. (They take longer to run, however, because they spend some time collecting timing statistics, whereas `@time` and `@elapsed` only run the code once.)
---
### Author:  [@RoyiAvital](https://discourse.julialang.org/u/RoyiAvital)
#### Post date: [October 12, 2019, 7:34am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/18 "2019-10-12T07:34:45Z")
Are there **functions** which replace `tic()` and `toc()`?
I want to calculate the time difference manually.
---
### Author:  [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)
#### Post date: [October 12, 2019, 7:36am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/19 "2019-10-12T07:36:28Z")
Use `ts = time()` and `time() - ts`.
---
### Author:  [@cormullion](https://discourse.julialang.org/u/cormullion)
#### Post date: [October 12, 2019, 9:56am UTC](https://discourse.julialang.org/t/tic-toc-toq-vs-elapsed/1681/20 "2019-10-12T09:56:04Z")
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