Re: [Bulk] Re: C vs C++

What about doing the packed decimal work in a C module wrapped in a c++ 
class?

On 2/17/2015 2:56 PM, Jevgeni Astanovski wrote:
> Mark,
>
> Spent some time and rewrote the API to use long long.
> However I have nothing to do about the data that I'm processing.
> I work in the finance area so effectively my API works not with
> numbers - rather with money.
> And all the money in the tables is kept as packed decimals.
> So what I did - I read packed decimals and immediately convert them to
> long long before I make some arithmetics with them.
> Result is still the same - 2 times slower than the C version...
>
> I'll now go and experiment with the benchmarking program of yours to
> see what consumes time. If conversion of packed to int (or long) is
> most ti,e consuming, then probably I'm digging in the wrong
> direction.....
>
>
>
> On Mon, Feb 16, 2015 at 9:38 PM, Mark S Waterbury
> <[email protected]> wrote:
>> Jevgeni:
>>
>> I can pretty much guarantee that using 64-bit integers will always win "big
>> time" over using packed decimal, even in ILE C/400, from a performance
>> standpoint.  All the more so, with ILE C++.
>>
>> Mark
>>
>>> On 2/16/2015 2:31 PM, Jevgeni Astanovski wrote:
>>>
>>> Mark, frankly speaking packed decimal was my suspect since I saw the
>>> difference. I saw the difference - it was intuitively clear that the
>>> implementations of packed decimal is fundamentally different in C and C++
>>> (however unclear why). What I'll do tomorrow, I'll write my own trivial
>>> benchmark using decimal arithmetics.
>>> Hopefully I shall see the difference.
>>> The program uses decimal (15,0), decimal (15,9) and decimal (11,7) - It
>>> seems that they all fit into 8 byte int.
>>> I'll then see which is better - staying on C and decimals or switch to C++
>>> and integers...
>>>
>>> Thanks,
>>> Jevgeni.
>>>    On Feb 16, 2015 8:29 PM, "Mark S Waterbury"
>>> <[email protected]>
>>> wrote:
>>>
>>>> Jevjeni:
>>>>
>>>> I just noticed near the bottom of your post, where you said:
>>>>
>>>>           Program makes a lot of calculations with packed decimal.
>>>>
>>>> There is a big difference in the way ILE C implements support for "packed
>>>> decimal" as a "native" data type -- versus the way it is "supported" in
>>>> ILE
>>>> C++ -- in ILE C, the compiler directly genrerates in-line code (in WCode
>>>> /
>>>> NMI)  to work on packed decimal data.  In the ILE C++ compiler, support
>>>> for
>>>> "packed decimal" is through a C++ library called "BCD" -- there are a lot
>>>> of macros and such defined in the QSYSINC/H include member named BCD ...
>>>> if
>>>> you take a peek at that member, I think you will see that this uses
>>>> "operator overloading" in C++ to trick the compiler into calling the
>>>> desired library functions when operations are performed on "packed
>>>> decimal"
>>>> data.
>>>>
>>>> This difference could easily account for the big differences you are
>>>> seeing.
>>>>
>>>> And then, you said:
>>>>
>>>>           ... is there anything that can be done about it?
>>>>
>>>> In C++, you could look into converting the packed decimal data into
>>>> 64-bit
>>>> integers, and then performing any calculations using those long integers.
>>>> This would be much faster than using packed decimal arithmetic, then
>>>> convert back to packed decimal format, if needed.  Or, just stick with
>>>> ILE
>>>> C/400 for those programs that require doing a lot of packed decimal
>>>> arithmetic operations.
>>>>
>>>> Hope that helps,
>>>>
>>>> Mark S. Waterbury
>>>>
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