1000 Random number generation and Total should be 2000

It's questionable whether numbers can be truly random given a constraint that they must sum to a certain figure but the following should work.

For simplicity, I've programmed it as a console application and leave it to you to incorporate it within your ASP.NET application:

using System;

using System.IO;

class Program

{

static Random rand = new Random();

static void Main()

{

double[] numbers = new double[1000];

double sum = 0.0;

// generate 1000 doubles between 0.5 and 3.0 inclusive

for(int i = 0; i < 1000; i++)

{

numbers[i] = 0.5 + rand.Next(0, 25001)/ 10000.00;

sum += numbers[i];

}

Console.WriteLine("Initial sum = {0}", sum);

if (sum > 2000.0)

{

// 'expected' sum is 1750 so it's very unlikely it will be > 2000

// but if it is, scale the numbers back so the sum is 2000

for(int i = 0; i < 1000; i++)

{

numbers[i] = 0.5 + (numbers[i] - 0.5) * 1500.0/(sum - 500.0);

}

else if (sum < 2000)

{

// scale up iteratively until a sum of 2000 is reached and no number exceeds 3.0

double temp;

double sum2 = sum;

double sum3 = 0.0;

while(sum2 < 2000.0)

{

for(int i = 0; i < 1000; i++)

{

temp = 0.5 + (numbers[i] - 0.5) * 1500.0/(sum2 - 500.0);

if (temp <= 3.0) numbers[i] = temp;

sum3 += numbers[i];

}

sum2 = sum3;

sum3 = 0.0;

Console.WriteLine("Adjusted sum = {0}", sum2);

}

// write random numbers to a file

sum = 0.0;

using(StreamWriter sw = new StreamWriter("randomnumbers.txt"))

{

foreach(double number in numbers)

{

// make absolutely sure numbers all still within range

if (number < 0.5 || number > 3.0)

{

Console.WriteLine("{0} is out of range", number);

}

// and sum is 2000

sum += number;

sw.WriteLine(number.ToString());

}

Console.WriteLine("Final sum = {0}", sum);

Console.ReadKey();

}

2 Replies

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Vulpes13y ago
Accepted answer
It's questionable whether numbers can be truly random given a constraint that they must sum to a certain figure but the following should work.

For simplicity, I've programmed it as a console application and leave it to you to incorporate it within your ASP.NET application:

using System;
using System.IO;

class Program
{
static Random rand = new Random();

static void Main()
{
double[] numbers = new double[1000];
double sum = 0.0;

// generate 1000 doubles between 0.5 and 3.0 inclusive
for(int i = 0; i < 1000; i++)
{
numbers[i] = 0.5 + rand.Next(0, 25001)/ 10000.00;
sum += numbers[i];
}

Console.WriteLine("Initial sum = {0}", sum);

if (sum > 2000.0)
{
// 'expected' sum is 1750 so it's very unlikely it will be > 2000
// but if it is, scale the numbers back so the sum is 2000

for(int i = 0; i < 1000; i++)
{
numbers[i] = 0.5 + (numbers[i] - 0.5) * 1500.0/(sum - 500.0);
}
}
else if (sum < 2000)
{
// scale up iteratively until a sum of 2000 is reached and no number exceeds 3.0
double temp;
double sum2 = sum;
double sum3 = 0.0;

while(sum2 < 2000.0)
{
for(int i = 0; i < 1000; i++)
{
temp = 0.5 + (numbers[i] - 0.5) * 1500.0/(sum2 - 500.0);
if (temp <= 3.0) numbers[i] = temp;
sum3 += numbers[i];
}

sum2 = sum3;
sum3 = 0.0;
Console.WriteLine("Adjusted sum = {0}", sum2);
}
}

// write random numbers to a file
sum = 0.0;

using(StreamWriter sw = new StreamWriter("randomnumbers.txt"))
{
foreach(double number in numbers)
{
// make absolutely sure numbers all still within range
if (number < 0.5 || number > 3.0)
{
Console.WriteLine("{0} is out of range", number);
}

// and sum is 2000
sum += number;
sw.WriteLine(number.ToString());
}
}

Console.WriteLine("Final sum = {0}", sum);
Console.ReadKey();
}
}
Satish Hirpara13y ago
Thanks a lot vulpes it worked :) can you give me same for sql server 2008?