Thread Subject: svmtrain does not respect boxconstraint

Below is an example of the case where SMO algorithm of svmtrain function (in matlabs bioinformation toolbox) does not respect the boxconstraints.

The value of boxconstraint parameter is passed as 20, one of the Alpha (dual variable) takes the value 22.5, which it should not.

The matlab version being used is R2010b.

Thanks

>> X = [1 1; 1 2; 1 3; 2 1; 2 2; 2 3; 3 1; 3 2; 3 3];
>> Y = [1; 1; 1; 1; -1; 1; -1; -1; -1];
>> [svm_struct, svIndex] = svmtrain(X, Y, 'METHOD', 'SMO', 'SMO_OPTS', opts, 'SHOWPLOT', true, 'BOXCONSTRAINT', 20, 'autoscale', false);
seqMinOpt finished
seqMinOpt status:
Number of iterations: 24
Execution time: 0.015600 seconds
Value of stopping criterion: 0.000000
Value of objective function: 47.000000
All SVs: 4
Free SVs: 3
---------------------------
>> svm_struct.Alpha

ans =

  -11.2500
   22.5000
  -13.2500
    2.0000

>>