Example program for dtpqrt

This example finds the basic solutions for the linear least squares problems
minimize Axi - bi 2 ,   i=1,2  
where b1 and b2 are the columns of the matrix B,
A = -0.57 -1.28 -0.39 0.25 -1.93 1.08 -0.31 -2.14 2.30 0.24 0.40 -0.35 -1.93 0.64 -0.66 0.08 0.15 0.30 0.15 -2.13 -0.02 1.03 -1.43 0.50   and  B= -2.67 0.41 -0.55 -3.10 3.34 -4.01 -0.77 2.76 0.48 -6.17 4.10 0.21 .  
A QR factorization is performed on the first 4 rows of A using dgeqrt after which the first 4 rows of B are updated by applying QT using dgemqrt. The remaining row is added by performing a QR update using dtpqrt; B is updated by applying the new QT using dtpmqrt; the solution is finally obtained by triangular solve using R from the updated QR.