Team Lion F2017

Group Members

Intel Parallel Studio vTune Amplifier

1. Jagmeet Bhamber
2. Shivam Gupta
3. Yong Kuk Kim

What is VTune Amplifier?

• A tool created by Intel to provide performance analysis on software.
• Offers both a GUI and command-line version for both Windows and Linux
• GUI only for OSX
• Basic features available on both Intel and AMD processors, but advanced features only for Intel

How to use it?

• Available as a standalone unit or part of the following packages:
  • Intel Parallel Studio XE Cluster Edition and Professional Edition
  • Intel Media Server Studio Professional Edition
  • Intel System Studio

Can be run on a local machine

Hotspots

Basic hotspot analysis

We used our workshop 6 as an example to demonstrate this particular aspect of Intel Vtune Amplifer

the image above shows the timings for each function

matmul_0 - represents serial version

matmul_1 - represents serial version with reverse logic

matmul_2 - uses cilk_for

matmul_3 - uses cilk_for and reducer hyperboject

matmul_4 - uses cilk_for, reducer and vectorization

Parallelism

Concurrency

• Best for visualizing thread parallelism on available cores, finding areas with high or low concurrency, and identifying serial bottlenecks in your code
• Provides information on how many threads were running at each moment during application execution
• Includes threads which are currently running or ready to run and therefore are not waiting at a defined waiting or blocking API
• Also shows CPU time while the hotspot was executing and estimates its effectiveness either by CPU usage or by Threads Concurrency

Results of Concurrency tests on Workshop 6

I ran the Concurrency test on each of the functions in Workshop 6. I isolated each function by commenting out all others, then ran them 1 by 1. This was to get an idea of how they perform on their own. Finally I ran them all together to see how the program runs overall.

matmul_0 (Serial)

double matmul_0(const double* a, const double* b, double* c, int n) {
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			double sum = 0.0;
			for (int k = 0; k < n; k++)
				sum += a[i * n + k] * b[k * n + j];
			c[i * n + j] = sum;
		}
	}
	double diag = 0.0;
	for (int i = 0; i < n; i++)
		diag += c[i * n + i];
	return diag;
}

matmul_1 (Serial with j-k loops reversed)

double matmul_1(const double* a, const double* b, double* c, int n) {
	
	for (int i = 0; i < n; i++) {
		for (int k = 0; k < n; k++) {
			double sum = 0.0;
			for (int j = 0; j < n; j++)
				sum += a[i * n + k] * b[k * n + j];
			c[i * n + k] = sum;
		}
	}
	double diag = 0.0;
	for (int i = 0; i < n; i++)
		diag += c[i * n + i];
	return diag;
}

matmul_2 (Cilk Plus with cilk_for)

double matmul_2(const double* a, const double* b, double* c, int n) {
	
	cilk_for (int i = 0; i < n; i++) {
		cilk_for (int j = 0; j < n; j++) {
			double sum = 0.0;
			for(int k = 0; k < n; k++) {
				sum += a[i * n + k] * b[k * n + j];
			}
			c[i * n + j] = sum;
		}
	}

	double diag = 0.0;
	for (int i = 0; i < n; i++)
		diag += c[i * n + i];
	return diag;
}

matmul_3 (+array notation, reducer)

double matmul_3(const double* a, const double* b, double* c, int n) {
	
	cilk_for(int i = 0; i < n; i++) {
		cilk_for(int j = 0; j < n; j++) {
			double sum = 0.0;
			for (int k = 0; k < n; k++) {
				sum += a[i * n + k] * b[k * n + j];
			}
			c[i * n + j] = sum;
		}
	}

	cilk::reducer_opadd <double> diag(0.0);
	cilk_for(int i = 0; i < n; i++) {
		diag += c[i * n + i];
	}
	return diag.get_value();
}

matmul_4 (+vectorization)

double matmul_4(const double* a, const double* b, double* c, int n) {
	
	cilk_for(int i = 0; i < n; i++) {
		cilk_for(int j = 0; j < n; j++) {
			double sum = 0.0;
#pragma simd
			for (int k = 0; k < n; k++) {
				sum += a[i * n + k] * b[k * n + j];
			}
			c[i * n + j] = sum;
		}
	}

	cilk::reducer_opadd <double> diag(0.0);
	cilk_for(int i = 0; i < n; i++) {
		diag += c[i * n + i];
	}
	return diag.get_value();
}

Final test with all functions

Locks & Waits

• Best for locating causes of low concurrency, such as heavily used locks and large critical sections.
• Locks are when threads are waiting too long on synchronization objects.
• Uses user-mode sampling and tracing collection to identify processes.
• This analysis shows time spent waiting on synchronizations.

references

https://en.wikipedia.org/wiki/VTune

https://software.intel.com/en-us/get-started-with-vtune

https://software.intel.com/en-us/vtune-amplifier-help-analysis-types

https://software.intel.com/en-us/vtune-amplifier-help-basic-hotspots-analysis

https://software.intel.com/en-us/vtune-amplifier-help-advanced-hotspots-analysis

https://software.intel.com/en-us/vtune-amplifier-help-concurrency-analysis

https://software.intel.com/en-us/vtune-amplifier-help-locks-and-waits-analysis

https://software.intel.com/en-us/vtuneampxe_hotspots_win_c

https://software.intel.com/en-us/vtuneampxe_locks_win_c