tflag is one of CV_ROW_SAMPLE or CV_COL_SAMPLE

if you put one sample per row of your trainmat, use CV_ROW_SAMPLE and a Mat(num_samples,1,CV32S) for resonses.

per row

  // TrainingMat            responses

  s a m p l e                  1
  s a m p l e                  2
  s a m p l e                  1
  s a m p l e                  2
  s a m p l e                  1

per col

  s s s s s     // trainingmat
  a a a a a
  m m m m m 
  p p p p p
  l l l l l
  e e e e e

  1 2 1 2 1     // responses