docs: public static void ensureNotSingular( DMatrixSparseCSC A , Random rand ) {
  //        if( A.numRows < A.numCols ) {
  //            throw new IllegalArgumentException("Fewer equations than variables");
  //        }
  
          int []s = UtilEjml.shuffled(A.numRows,rand);
          Arrays.sort(s);
  
          int N = Math.min(A.numCols,A.numRows);
          for (int col = 0; col < N; col++) {
              A.set(s[col],col,rand.nextDouble()+0.5);
          }
      }