Different performance between Intel C++ Compiler 11 and Intel C++ Compiler 14

[Tam_N_]

Hi all,

I have some problems with my source code, when I build it with Intel C++ Compiler 11 and Intel C++ Compiler 14. The difference is showed at the table below:

	Intel Compiler 11	Intel Compiler 14
Original source (ms)	120	110
Optimized source (ms)	100	110

With:

+ Original source: I use many variables to store data and calculate on it.

+ Optimized source: I use a struct to store variables on original source and vectorize my calculations. Moreover, I have removed some redundant calculations.

I don't know the reason for this difference between two sources above.

Please help me explain this difference ?

Tam Nguyen

[TimP]

If you aren't willing to show the example, you may need to compare opt reports and asm files to see if there is a reason.  Such small differences may be due to effects beyond your control.

[bernaske]

Hi,

i have the same situation under Linux , we use a testsuite from nearly 12 testprograms, dhrystone, whetstone, scimark2c , flops,

and so far and compile it with the gcc-4.9, gcc-4.8.3 , icc 15.0.0 (Cluster_Studio_XE 2015 Beta ), pathscale and pgi c/c++ compilers

for all we use -O3 -m64 -mtune=corei7 as compile options on dhrystone, whetstone, livermoore loops , flops was the intel compiler

absolut the fastest, only on the scimark2c benchmark was the gcc-4.9 absolut the fastest between 8 to 10 % faster then the

Intel C/C++ compiler, all on the same hardware, ASUS P6T6 WS Revolution Motherboard Intel i7-950 with stable at 4.00 Ghz

24 Gbyte RAM DDR3 XMS, two GeForce GTX560 Ti in SLI Mode, openSUSE 13.2 M0 64 Bit Linux Kernel 3.15.1, KDE 4.13.40,

actual NVIDIA Driver 334.17

best regards

Franz

[Bernard]

You should compare asm code generated by both compiler version just exactly as Tim said.

[QIAOMIN_Q_]

Hello Tam,

Can you provide the sample code in question? And what's the specific versions and compilation options for both compilers?

Thank you.
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QIAOMIN.Q
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