Re: C vs C++

No chance, Charles.
All three are compiled in 2 phases and all three use ACTGRP(*CALLER).


On Mon, Feb 16, 2015 at 5:10 PM, Charles Wilt <[email protected]> wrote:
> Any chance your C++ programs are using ACTGRP(*NEW) and the C ones are not?
>
> Charles
>
> On Mon, Feb 16, 2015 at 9:56 AM, Jevgeni Astanovski <[email protected]>
> wrote:
>
>> Hi all.
>> Does anyone have any idea why C++ program is significantly slower than
>> C program?
>>
>> Explain the situation.
>> I have a number of API-s that are called via RPC, access some tables,
>> make some calculations and return some structures to the caller.
>> They've all been written on ILE/C.
>> Recently I started to experiment with porting them to ILE/C++. There
>> was a number of reasons why it would be nice.
>> After I rewrote the first one, I started to measure performance. This
>> is an issue for me as some of them are called hundreds of thousands
>> times per day.
>> Found out that it is approximately 2 times slower than C version.
>> Shared a code to colleges - no one found anything suspicious. However
>> one guy came out with a "brilliant" idea - he advised me to try to
>> recompile my C program with CPP compiler and see the performance.
>> Guess what? C program compiled with CPP compiler was the same 2 times
>> slower than C program compiled with C compiler....
>>
>> And the only modifications that I did for compiling C with CPP compiler
>> was:
>> 1. Substituted "#pragma mapinc" table structue definitions with those
>> generated by GENCSRC;
>> 2. Changed char and unsigned char in a couple of places as C++ is more
>> strict;
>> 3. Made a substitution for "NNNND" constants (like 100D for example)
>> as C++ does not support that.
>>
>> What I saw is that time increase looks like it has a proportional nature.
>> I tested API in 3 cases (number of tests is over 100): simple request,
>> medium request; complicated request and the timing is:
>> Simple C: 1ms; Simple C++ : 2ms
>> Medium C: 3ms; Simple C++ : 7ms
>> Long C: 25ms; Long C++: 60ms.
>>
>> The difference is in number of records read from table and a number of
>> calculations.
>> That is a simple one retrieves less that 10 records; medium - more
>> than 10 and long - more than 100. Program makes a lot of calculations
>> with packed decimal.
>>
>> Any idea why it is like that and is there anything that can be done about
>> it?
>>
>> Thanks in advance,
>>
>> Jevgeni.
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