public static void Main(string[] args)
{
// demo();
Console.Write("Denominator: ");
long div = long.Parse(Console.ReadLine());
Console.Write("Max enumerator: ");
long max = long.Parse(Console.ReadLine());
long mul;
int shift;
if (Optimize.FindMulShift(max, div, out mul, out shift))
{
string msg = " n / " +
div.ToString() + "\t <==> n * " + mul.ToString() + " >> " + shift.ToString();
System.Console.WriteLine(msg);
}
else
{
System.Console.WriteLine(div.ToString() + " not found");
}
System.Console.ReadLine();
}
public static void demo()
{
long mul = 0;
int shift = 0;
long div = 0;
long max = 0;
int high = 1000;
int maxdiv = 100;
int iterations = 1000;
// some doubles to average timing
double avg = 0;
double s1;
double s2;
HiPerfTimer pt = new HiPerfTimer();
#region example I
pt.Start();
for (div = 1; div < 100; div++)
{
max = 1000; // 1L<<30; // = 2^30
if (Optimize.FindMulShift(max, div, out mul, out shift))
{
string msg = " / " +
div.ToString() + "\t <==> * " + mul.ToString() + " >> " + shift.ToString();
System.Console.WriteLine(msg);
}
else
{
System.Console.WriteLine(div.ToString() + " not found");
System.Console.ReadLine();
}
}
pt.Stop();
System.Console.WriteLine("done, " + pt.Duration().ToString("0.00"));
System.Console.ReadLine();
#endregion
#region performance measurement /
//
// How much faster is it?
//
avg = 0;
System.Console.WriteLine("start / ");
for (div = -maxdiv; div <= maxdiv; div++)
{
if (div == 0)
{
continue;
}
Optimize.FindMulShift(high, div, out mul, out shift);
// normal div timing,
pt.Start();
long x = 0;
for (int i = 0; i < iterations; i++)
{
for (int j = -high; j < high; j++)
{
x = j / div;
}
}
pt.Stop();
s1 = pt.Duration();
// mul shift timing,
// with fixed dividers, the if then else construct will be simpler!!
// just as example how to handle negative dividers
pt.Start();
for (int i = 0; i < iterations; i++)
{
for (int j = -high; j < high; j++)
{
if (j >= 0)
{
if (div > 0)
{
x = ((j * mul) >> shift);
}
else
{
x = -((j * mul) >> shift);
}
}
else
{
if (div > 0)
{
x = -((-j * mul) >> shift);
}
else
{
x = ((-j * mul) >> shift);
}
}
}
}
pt.Stop();
s2 = pt.Duration();
double d = 100 - 100 * s2 / s1;
System.Console.WriteLine(div + "\t"
+ s1.ToString("0.000")
+ "\t" + s2.ToString("0.000")
+ "\tperc: " + d.ToString("0.00"));
avg += d;
}
// TODO: remove hard coded average
System.Console.WriteLine("average: " + (avg / maxdiv / 2).ToString("0.00"));
System.Console.WriteLine("done");
System.Console.ReadLine();
#endregion
#region performance measurement %
//
// How much faster is it?
//
avg = 0;
System.Console.WriteLine("start %");
for (div = -maxdiv; div <= maxdiv; div++)
{
if (div == 0)
{
continue;
}
Optimize.FindMulShift(high, div, out mul, out shift);
// normal div timing,
pt.Start();
long x = 0;
for (int i = 0; i < iterations; i++)
{
for (int j = -high; j < high; j++)
{
x = j % div;
}
}
pt.Stop();
s1 = pt.Duration();
// mul shift timing,
// with fixed dividers, the if then else construct will be simpler!!
pt.Start();
for (int i = 0; i < iterations; i++)
{
//long y = 0;
for (int j = -high; j < high; j++)
{
if (j >= 0)
{
if (div > 0)
{
x = j - ((j * mul) >> shift) * div;
}
else
{
x = j - ((j * mul) >> shift) * -div;
}
}
else
{
if (div > 0)
{
x = j + ((-j * mul) >> shift) * div;
}
else
{
x = j + ((-j * mul) >> shift) * (-div);
}
}
// if (x != j%div)
// {
// Console.WriteLine(j + " " + div + " "+ x + " " + y);
// }
}
}
pt.Stop();
s2 = pt.Duration();
double d = 100 - 100 * s2 / s1;
System.Console.WriteLine(div + "\t"
+ s1.ToString("0.000")
+ "\t" + s2.ToString("0.000")
+ "\tperc: " + d.ToString("0.00"));
avg += d;
}
System.Console.WriteLine("average: " + (avg / maxdiv / 2).ToString("0.00"));
System.Console.WriteLine("done");
System.Console.ReadLine();
#endregion
#region performance measurement / (positive only)
//
// How much faster is it?
//
avg = 0;
System.Console.WriteLine("start / (only positive values)");
for (div = 1; div <= maxdiv; div++)
{
if (div == 0)
{
continue; // allows div to start with -maxdiv
}
Optimize.FindMulShift(high, div, out mul, out shift);
// normal div timing,
pt.Start();
long x = 0;
for (int i = 0; i < iterations; i++)
{
for (int j = 0; j < high; j++)
{
x = j / div;
}
}
pt.Stop();
s1 = pt.Duration();
// mul shift timing,
// with fixed dividers, the if then else construct will be simpler!!
pt.Start();
for (int i = 0; i < iterations; i++)
{
for (int j = 0; j < high; j++)
{
x = ((j * mul) >> shift);
}
}
pt.Stop();
s2 = pt.Duration();
// calculate gain
double d = 100 - 100 * s2 / s1;
System.Console.WriteLine(div + "\t"
+ s1.ToString("0.000")
+ "\t" + s2.ToString("0.000")
+ "\tperc: " + d.ToString("0.00"));
avg += d;
}
System.Console.WriteLine("average: " + (avg / maxdiv).ToString("0.00"));
System.Console.WriteLine("done");
System.Console.ReadLine();
#endregion
} // Main
