Performance Testing 1

PerformanceTesting.java

// Generate data
int arraySize = 32768;
int data[] = new int[arraySize];

Random rnd = new Random(0);
for (int c = 0; c < arraySize; ++c)
    data[c] = rnd.nextInt() % 256;

// notice !!!
Arrays.sort(data);

// Test
long start = System.nanoTime();
long sum = 0;

for (int i = 0; i < 100000; ++i)
{
    // Primary loop
    for (int c = 0; c < arraySize; ++c)
    {

        if (data[c] >= 128)
            sum += data[c];     
    }
}

System.out.println((System.nanoTime() - start) / 1000000000.0);
System.out.println("sum = " + sum);

PerformanceTesting2.java

// Generate data
int arraySize = 32768;
int data[] = new int[arraySize];

Random rnd = new Random(0);
for (int c = 0; c < arraySize; ++c)
    data[c] = rnd.nextInt() % 256;

// notice !!!
Arrays.sort(data);

// Test
long start = System.nanoTime();
long sum = 0;


for (int i = 0; i < 100000; ++i)
{
    // Primary loop
    for (int c = 0; c < arraySize; ++c)
    {
        int t = (data[c] - 128) >> 31;
        sum += ~t & data[c];
    }
}

System.out.println((System.nanoTime() - start) / 1000000000.0);
System.out.println("sum = " + sum);

PerformanceTesting3.java

// Generate data
int arraySize = 32768;
int data[] = new int[arraySize];

Random rnd = new Random(0);
for (int c = 0; c < arraySize; ++c)
    data[c] = rnd.nextInt() % 256;

// notice !!!
Arrays.sort(data);

// Test
long start = System.nanoTime();
long sum = 0;


for (int i = 0; i < 100000; ++i)
{
    // Primary loop
    for (int c = 0; c < arraySize; ++c)
    {
        // Test 3
        sum += data[c] >=128 ? data[c] : 0;
    }
}
System.out.println((System.nanoTime() - start) / 1000000000.0);
System.out.println("sum = " + sum);

PerformanceTesting4.java

// Generate data
int arraySize = 32768;
int data[] = new int[arraySize];

Random rnd = new Random(0);
for (int c = 0; c < arraySize; ++c)
    data[c] = rnd.nextInt() % 256;

// notice !!!
Arrays.sort(data);

// Test
long start = System.nanoTime();
long sum = 0;

for (int j = 0; j < arraySize; ++j)
{
    if (data[j] >= 128)
    {
        sum += data[j] * 100000;
    }
}

System.out.println((System.nanoTime() - start) / 1000000000.0);
System.out.println("sum = " + sum);