On 7/15/21 5:13 PM, Lucretia wrote:
>
> I managed to get just under 4000 passes with a 1 bit array, but not using Ada's packed array. That's actually the slowest method, strangely.

So you have an array of a modular type, calculate an index and bit within it,
mask out that bit, and compare it to zero? I would have thought an unpacked
array of Boolean would be fastest.

A packed array of Boolean requires all the operations above, plus shifting the
bit to the LSB and treating the result as a Boolean, so it may not be that
surprising that it's slower.

--
Jeff Carter
"How'd you like to hide the egg and gurgitate
a few saucers of mocha java?"
Never Give a Sucker an Even Break
101

On Thursday, July 15, 2021 at 8:56:40 AM UTC-7, Jeffrey R. Carter wrote:
> On 7/15/21 5:13 PM, Lucretia wrote:
> >
> > I managed to get just under 4000 passes with a 1 bit array, but not using Ada's packed array. That's actually the slowest method, strangely.
> So you have an array of a modular type, calculate an index and bit within it,
> mask out that bit, and compare it to zero? I would have thought an unpacked
> array of Boolean would be fastest.
>
> A packed array of Boolean requires all the operations above, plus shifting the
> bit to the LSB and treating the result as a Boolean, so it may not be that
> surprising that it's slower.

Should fixed lower bound index array (-gnatX) speed it up?

Anh Vo

On Thursday, 15 July 2021 at 16:56:40 UTC+1, Jeffrey R. Carter wrote:
> On 7/15/21 5:13 PM, Lucretia wrote:
> >
> > I managed to get just under 4000 passes with a 1 bit array, but not using Ada's packed array. That's actually the slowest method, strangely.
> So you have an array of a modular type, calculate an index and bit within it,
> mask out that bit, and compare it to zero? I would have thought an unpacked
> array of Boolean would be fastest.

Doesn't seem to be. Also, the guy is using the packed bit as the final test of all the languages.

> A packed array of Boolean requires all the operations above, plus shifting the
> bit to the LSB and treating the result as a Boolean, so it may not be that

Don't need to shift to the LSB, only need to shift the 1 to the bit location you want to test, invert and then check against 0.

> surprising that it's slower.

I know. I would've thought the compiler would've handled the packed array as a special case and optimised as much as possible there.

On 2021-07-15 18:29, Lucretia wrote:
> On Thursday, 15 July 2021 at 16:56:40 UTC+1, Jeffrey R. Carter wrote:
>> On 7/15/21 5:13 PM, Lucretia wrote:
>>>
>>> I managed to get just under 4000 passes with a 1 bit array, but not using Ada's packed array. That's actually the slowest method, strangely.
>> So you have an array of a modular type, calculate an index and bit within it,
>> mask out that bit, and compare it to zero? I would have thought an unpacked
>> array of Boolean would be fastest.
>
> Doesn't seem to be.

Unlikely unless compiled into machine-specific instructions. You should
inspect the code.

> Also, the guy is using the packed bit as the final test of all the languages.
>
>> A packed array of Boolean requires all the operations above, plus shifting the
>> bit to the LSB and treating the result as a Boolean, so it may not be that
>
> Don't need to shift to the LSB, only need to shift the 1 to the bit location you want to test, invert and then check against 0.

Usually masks are either tabulated in a look-up table or are constants
in a case choice.

>> surprising that it's slower.
>
> I know. I would've thought the compiler would've handled the packed array as a special case and optimised as much as possible there.

It is still unlikely to be faster than all arrays. You should probably
try to use different element types and inspect the code.

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

On Thursday, 15 July 2021 at 17:29:52 UTC+1, Anh Vo wrote:

> > A packed array of Boolean requires all the operations above, plus shifting the
> > bit to the LSB and treating the result as a Boolean, so it may not be that
> > surprising that it's slower.
> Should fixed lower bound index array (-gnatX) speed it up?

On GCC 9.3.0:

-gnatX Language extensions permitted

On 7/15/21 6:29 PM, Lucretia wrote:
> On Thursday, 15 July 2021 at 16:56:40 UTC+1, Jeffrey R. Carter wrote:
>
>> A packed array of Boolean requires all the operations above, plus shifting the
>> bit to the LSB and treating the result as a Boolean, so it may not be that
>
> Don't need to shift to the LSB, only need to shift the 1 to the bit location you want to test, invert and then check against 0.

You know that that is enough, and may be what you're doing manually, but the
compiler may not know that. If A is a packed array of Boolean, then A (I) has
type Boolean. Unless the compiler can optimize it (and maybe it can), it would
normally need to shift the bit down so it can be treated as a value of type
Boolean, and then apply whatever you do with the resulting Boolean value.

--
Jeff Carter
"How'd you like to hide the egg and gurgitate
a few saucers of mocha java?"
Never Give a Sucker an Even Break
101

Lucretia <laguest9000@googlemail.com> writes:

> On Thursday, 15 July 2021 at 17:29:52 UTC+1, Anh Vo wrote:
>
>> > A packed array of Boolean requires all the operations above, plus
>> > shifting the
>> > bit to the LSB and treating the result as a Boolean, so it may not be that
>> > surprising that it's slower.
>> Should fixed lower bound index array (-gnatX) speed it up?
>
> On GCC 9.3.0:
>
> -gnatX Language extensions permitted

Ah, but which ones?

Lucretia <laguest9000@googlemail.com> writes:

> On Thursday, 15 July 2021 at 17:29:52 UTC+1, Anh Vo wrote:
>
>> > A packed array of Boolean requires all the operations above, plus
>> > shifting the bit to the LSB and treating the result as a Boolean,
>> > so it may not be that surprising that it's slower.
>> Should fixed lower bound index array (-gnatX) speed it up?
>
> On GCC 9.3.0:
>
> -gnatX Language extensions permitted

Ah, but which ones?

I doubt if any industrial software engineering in Aviations, railroads, control system in Europe or in the US, beyond, web programmers are going to abandon Ada, back to Pascal, over such kiddy code comparisons.

Mace Ayres <mace.ayres@icloud.com> writes:
> I doubt if any industrial software engineering in Aviations,
> railroads, control system in Europe or in the US, beyond, web
> programmers are going to abandon Ada, back to Pascal, over such kiddy
> code comparisons.

It's still a matter of concern if straightforward code is that much
harder to compile with Ada, that an advanced Ada compiler (GNAT)
produces slower code than a relatively simple Pascal compiler does
(depending on what Pascal compiler it was, of course).

On Thursday, July 15, 2021 at 9:29:52 AM UTC-7, Anh Vo wrote:
> On Thursday, July 15, 2021 at 8:56:40 AM UTC-7, Jeffrey R. Carter wrote:
> > On 7/15/21 5:13 PM, Lucretia wrote:
> > >
> > > I managed to get just under 4000 passes with a 1 bit array, but not using Ada's packed array. That's actually the slowest method, strangely.
> > So you have an array of a modular type, calculate an index and bit within it,
> > mask out that bit, and compare it to zero? I would have thought an unpacked
> > array of Boolean would be fastest.
> >
> > A packed array of Boolean requires all the operations above, plus shifting the
> > bit to the LSB and treating the result as a Boolean, so it may not be that
> > surprising that it's slower.
> Should fixed lower bound index array (-gnatX) speed it up?

Indeed, it does. As posted on Reddit Ada, I got 5476 Passes after changing array types to arrays having fixed lower bound index of 0 on lines 9 and 10 and compiling it using switch -gnatX -02. By the way, I used GNAT Studio 2021 running on Windows 10.

On 23/07/2021 18:04, Anh Vo wrote:

>> Should fixed lower bound index array (-gnatX) speed it up?
>
> Indeed, it does. As posted on Reddit Ada, I got 5476 Passes after changing array types to arrays having fixed lower bound index of 0 on lines 9 and 10 and compiling it using switch -gnatX -02. By the way, I used GNAT Studio 2021 running on Windows 10.
>

I as I stated that flag enables gnat extensions, usually the next
language revision. I'm on the FSF compiler, the dockerfile is set of gcc 11.

On 16/07/2021 17:28, Simon Wright wrote:
> Lucretia <laguest9000@googlemail.com> writes:
>
>> On Thursday, 15 July 2021 at 17:29:52 UTC+1, Anh Vo wrote:
>>
>>>> A packed array of Boolean requires all the operations above, plus
>>>> shifting the bit to the LSB and treating the result as a Boolean,
>>>> so it may not be that surprising that it's slower.
>>> Should fixed lower bound index array (-gnatX) speed it up?
>>
>> On GCC 9.3.0:
>>
>> -gnatX Language extensions permitted
>
> Ah, but which ones?
>

Oh, I now think it's the 2012 extension which enables you do have (1 ..
<>) or (0 .. <>) in array types, rather than a more useful command line
option to normalise array indices to 0.