Author: Dann Corbit
Date: 13:35:57 10/13/99
Go up one level in this thread
Here is my interpretation of the USCF rules for ELO calculation:
#include <stdio.h>
#include <math.h>
#include "uscf.h"
double
provisional_rating (
double opponent_average_rating,
unsigned wins,
unsigned draws,
unsigned losses
)
{
double new_rating;
if (wins + draws + losses == 0)
new_rating = 0.;
else
new_rating = opponent_average_rating +
(400.0 * ((wins + 0.5 * draws) - (0.5 * draws + losses)) /
(wins + draws + losses));
return (double) (unsigned) (new_rating + 0.5);
}
double
established_rating (
double old_rating,
double event_score,
double rating_difference,
char half_k_event,
double prize_amount,
unsigned event_level
)
{
double rating;
double k = old_rating >= 2400.0 ? 16.0 : old_rating >= 2100.0 ? 24.0 : 32.0;
if (half_k_event)
k *= 0.5;
rating = old_rating + k * (event_score - win_expectancy (rating_difference));
if (old_rating <= 2099.0 &&
rating >= 2100.0 &&
rating <= 2399.0)
rating = 2100.0 + (rating - 2100.0) * 0.75;
else if (old_rating >= 2100.0 &&
old_rating <= 2399.0 &&
rating <= 2099.0)
rating = 2100.0 * (rating - 2100.0) * 1.33;
else if (old_rating >= 2100.0 &&
old_rating <= 2399.0 &&
rating >= 2400.0 &&
rating <= 3000.0)
rating = 2400.0 * (rating - 2400.0) * 0.66;
else if (old_rating >= 2400.0 &&
old_rating <= 3000.0 &&
rating >= 2100.0 &&
rating <= 2399.0)
rating = 2400.0 * (rating - 2400.0) * 1.50;
return rating_floor_adj (old_rating, rating, prize_amount, event_level);
}
double
win_expectancy (
double rating_difference
)
{
return 1.0 / (pow (10.0, (rating_difference / 400.0)) + 1.);
}
double
rating_floor_adj (
double old_rating,
double new_rating,
double prize_amount,
unsigned event_level
)
{
char large_cash_prize = 0;
double temp_floor = old_rating - 200.0;
unsigned ltf = ((unsigned) (temp_floor)) % 100UL * 100UL;
if (old_rating >= 2400 || old_rating <= 100)
return new_rating;
if (old_rating < 1600)
ltf = 100;
if (old_rating < 2200 && prize_amount >= 1000)
large_cash_prize = 1;
else if (old_rating < 2300 && prize_amount >= 1500)
large_cash_prize = 1;
else if (old_rating < 2400 && prize_amount >= 2000)
large_cash_prize = 1;
if (large_cash_prize)
ltf = event_level;
return ltf > new_rating ? (double) ltf : new_rating;
}
unsigned long
rating_floor (
double old_rating,
double new_rating,
double prize_amount,
unsigned event_level
)
{
char large_cash_prize = 0;
unsigned floor_value = (((unsigned) (old_rating - 200)) % 100U) * 100U;
if (old_rating >= 2400 || old_rating <= 100)
return (unsigned long) (new_rating + 0.5);
if (old_rating < 1600)
floor_value = 100;
if (old_rating < 2200 && prize_amount >= 1000)
large_cash_prize = 1;
else if (old_rating < 2300 && prize_amount >= 1500)
large_cash_prize = 1;
else if (old_rating < 2400 && prize_amount >= 2000)
large_cash_prize = 1;
if (large_cash_prize)
floor_value = event_level;
return floor_value;
}
const char *
describe_uscf_rating (
unsigned rating
)
{
char *rating_name;
if (rating > 2399)
rating_name = "Senior Master";
else if (rating >= 2200)
rating_name = "Master";
else if (rating >= 2000)
rating_name = "Expert";
else if (rating >= 1800)
rating_name = "Class A";
else if (rating >= 1600)
rating_name = "Class B";
else if (rating >= 1400)
rating_name = "Class C";
else if (rating >= 1200)
rating_name = "Class D";
else if (rating >= 1000)
rating_name = "Class E";
else if (rating >= 800)
rating_name = "Class F";
else if (rating >= 600)
rating_name = "Class G";
else if (rating >= 400)
rating_name = "Class H";
else if (rating >= 200)
rating_name = "Class I";
else
rating_name = "Class J";
return rating_name;
}
int
main (void)
{
double rating_difference;
double ameteur = 1351.;
for (rating_difference = 0; rating_difference <= 3000; rating_difference +=
100)
{
printf ("Win expectency for a difference of %.0f points is %g\n",
rating_difference,
win_expectancy (rating_difference));
}
printf ("%.15g\n", win_expectancy (1800. - 1351.) *
win_expectancy (2004. - 1351.) *
win_expectancy (1938. - 1351.) *
win_expectancy (1786. - 1351.));
printf ("%.15g\n", win_expectancy (1800. - 1351.));
printf ("%.15g\n", win_expectancy (2004. - 1351.));
printf ("%.15g\n", win_expectancy (1938. - 1351.));
printf ("%.15g\n", win_expectancy (1786. - 1351.));
printf ("%.15g\n", win_expectancy (2500. - 2260.));
printf ("%.15g\n", win_expectancy (2200. - 1700.));
return 0;
}
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Last modified: Thu, 15 Apr 21 08:11:13 -0700
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