The basis for calculating ratings at a solving tournament is the average of ratings of all solvers with ratings (AveRat) and the average of achieved results of those solvers (AveRes).

AveRat = average rating of all solvers with ratings (subtracting by 1600)
AveRes = average result of all solvers with ratings

A rating for a solver without a rating:

It is calculated as a performance rating (PerfRat), i.e. a temporary rating achieved by a solver at a tournament upon the formula:

PerfRat = AveRat x Res / AveRes
Res = result of a solver achieved at a tournament

Solver's first rating is called half-rating. At his next tournament he gets another half-rating. The average of all half-ratings is calculated and put to the rating list.

Change of a rating for a solver with a rating:

The expected result (ExpRes) is calculated for all solvers with ratings upon the formula:

ExpRes = AveRes x Rat / AveRat
Rat = rating of a solver from the last rating list

The expected result might exceed 100% of the winner's result. In such case the corrections (CorrExpRes and CorrPerfRat) are made upon the formulas:

CorrExpRes = AveRes + (ExpRes - AveRes) x (MaxRes - AveRes) / ( MaxExpRes - AveRes)
CorrExpRes = corrected expected result (cannot exceed 100% of the winner's result)
MaxRes = result of the winner
MaxExpRes = the highest expected result before correction (higher than the winner's result)

CorrPerfRat = AveRat + (PerfRat - AveRat) / (MaxPerfRat - AveRat) x (MaxRes x MaxRat / MaxCorrExpRes - AveRat)
CorrPerfRat = corrected performance rating
MaxRat = the highest solver's rating
MaxPerfRat = performance rating of the winner
MaxCorrExpRes = the highest corrected expected result

A change of a rating (ChOfRat) is calculated from the difference between the expected result and the achieved result upon the formula:

ChOfRat = KT x (Res - ExpRes)
or in a case of correction:
ChOfRat = KT x (Res - CorrExpRes)
KT = tournament coefficient (from 1 to 4)

If the problems at the tournament are not given 5 points each the KT is corrected upon the formula:

CorrKT = KT x 5 x N / AbsMaxRes
CorrKT = corrected tournament coefficient
N = number of problems at the tournament
AbsMaxRes = theoretical MaxRes at the tournament

New rating is calculated upon the formula:

NewRat = Rat + ChOfRat

If NewRat is negative it is corrected to zero. All calculations are made to the second decimal place. Ratings are published as integers. For publishing use the ratings are increased by 1600.

After five years of non-participating at the rated tournaments a solver is expelled from the rating (half-rating) list. For the further participation his original rating (but not half-rating) is accepted.

Ratings are calculated after each tournament. An updated rating list is published twice a year (at 1st January and 1st July).

A frame for coefficients for tournaments organised according to the WCSC rules:

Coefficient	Criteria for tournament
4	WCSC, ECSC
3	WCSC-type tournament for norms
2.5	participation at least 5 solvers with rating 2300 or higher
2	participation at least 5 solvers with rating 2200 or higher
1.5	participation at least 5 solvers with rating 2100 or higher
1	Others tournaments organised according to the WCSC rules

A frame for coefficients for tournaments organised according to others rules:

Coefficient	Criteria for tournament
2	WCCC-Open
1.5	ISC, not-WCSC-type tournament for norms
1	Others tournaments

The representative (commission) has the right to confirm or not the acceptability of the tournament and determines the tournament coefficient.

This version of the rules was accepted at the PCCC Congress in Wageningen 2006.

Last update  08-X-06

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