Also-rans: the global math/rand functions are thread safe (drawing a random
number is protected by a mutex.)
If the Java one isn't thread safe, you are comparing apples with oranges.
Try creating a local rand.Rand and see what gives.
HTH,
-s
sent from my droid
On Fri, Jan 25, 2019, 07:45 Michael Jones <michael.jo...@gmail.com wrote:
> Also...pseudo-random number generation is not a specific computation;
> there are many ways to do it--some faster some slower, some better some
> worse. If you want to time a general poisson disc simulation you would be
> better with a grid than calls to rand() because now you are testing the
> speed of the chosen random number generator.
>
> For comparison, your fmt.Println(calPi(100000000)) with the standard
> (locking) prng on my notebook:
>
> 3.14151812
> real 0m5.123s
>
> versus a one-thread high-quality prng:
>
> 3.14154348
> real 0m1.395s
>
> The speedup shows that you are just testing random number generation speed.
>
> The same computation with a grid of pointCount points...
>
> root := math.Sqrt(float64(pointCount))
> d := 2 / root
> for x := -1.0; x < 1.0; x += d {
> for y := -1.0; y < 1.0; y += d {
> if x*x+y*y < 1 {
> inCircleCount++
> }
> }
> }
>
> ...gives:
>
> 3.14158668
> real 0m0.170s
>
> So, 5.123 or 1.395 or 0.170 seconds based on how the sample points are
> calculated. Performance testing is hard.
>
> Michael
>
> On Thu, Jan 24, 2019 at 8:48 PM Ian Lance Taylor <i...@golang.org> wrote:
>
>> On Thu, Jan 24, 2019 at 7:01 PM Karthik Krishnaswamy
>> <karthik.krishnaswam...@gmail.com> wrote:
>> >
>> > I am just curious to understand what is the best possible way to
>> increase the execution speed of this particular program ? I am still
>> learning go though :)
>>
>> To speed up that particular program, don't use recursive Fibonacci.
>> The recursive function that you wrote has complexity O(2 ** N). Write
>> a simple loop, complexity O(N).
>>
>> Ian
>>
>>
>> > On Fri, Jan 25, 2019 at 8:26 AM Ian Lance Taylor <i...@golang.org>
>> wrote:
>> >>
>> >> On Thu, Jan 24, 2019 at 6:21 PM Topget <topget1...@gmail.com> wrote:
>> >> >
>> >> > I have tested several simple functions with Golang and Java. To my
>> surprise, Java sometimes is faster than Golang（especially in recursive
>> function and some function in standard library such as math/rand.Rand）. I
>> wonder why. Here is some code I used for test and the result.
>> >>
>> >> Because goroutines start with a small stack that grows as needed,
>> >> deeply recursive functions will tend to have somewhat worse behavior
>> >> the first time they are called.
>> >>
>> >> Ian
>> >>
>> >> --
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>
>
> --
>
> *Michael T. jonesmichael.jo...@gmail.com <michael.jo...@gmail.com>*
>
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