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tony3
Beginner
83 Views

Simple problem

Hi,
I'm messing around, trying to get the hang on VTune and I have the following query:
I wrote myself a very simple console app to put though a series of tests. Effectively all it does is fill a 3d array column first and then row first. Obviously this causes a lot of cache trashing (right?) when doing it column first.
const int g_n = 250;
float TestData[g_n][g_n][g_n];
void Col(void)
{
for(int k=0;k for(int j=0;j
for(int i=0;i TestData = 0.0f;
}
void Row(void)
{...}
int main(void)
{
Row(); Col();
}
Ok so I sample and VTune notices that the Col() function is doing something wrong but the tuning assistant advice is pretty obscure:
Poor Nominal CPI : advice - more measurements should be taken to determine exactly what steps should be taken to improve performance.
What exactly does this mean? what does it what me to do and how?
Also when running a call graph test on the same chunk of code it shows me a lot of stuff from kernel32.dll and ntdll.dll but NOTHING from my test project test.exe. Why is this? surely it should see main() and Row() and Col() ??
I am most confused!
Many Thanks in advance
Anthony
0 Kudos
3 Replies
David_A_Intel1
Employee
83 Views

Tony:

Basically, the Tuning Assistant is telling you that there is not enough information to deduce any problems. When you create an activity with the Sampling Wizard, you have the option to tell the assistant how many runs to use to collect information. If you selected "One sampling run...", then you need to create a new activity and select "A few sampling runs..." or "Many sampling runs...". This will give the assistant more information from which to deduce the problem.

Regarding call graph, did you receive a message about your application not having base relocations? If you application is not linked with "/fixed:no", or otherwise has base relocations turned off, call graph will not be able to instrument your application and, consequently, there will be no data collected or displayed for it. See the online help for more info.

tony3
Beginner
83 Views

Hello and thanks for answering.

I can't seem to find the "A few sampling runs..." or "Many sampling runs..." option you speak of. I'm using VTune 7.0.

As for the call graph problem, I figured it out. Yes I was linking with '/fixed:no' except my compiler only pays attention to this when typed in capitals! :$

Thanks

Anthoy

David_A_Intel1
Employee
83 Views

Hi Anthony:

Oh, sorry. Yes, these options are new to 7.1. If you purchased 7.0 and registered your serial number, you should be entitled to a free upgrade. Based on your purchase date, you receive one year of support services, including free upgrades. The 7.1 installation package can be downloaded from http://premier.intel.com.

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