Added example for pivoting QR.

Author: loiseaujc

example/linalg/CMakeLists.txt

@@ -54,6 +54,7 @@ ADD_EXAMPLE(svdvals)
 ADD_EXAMPLE(determinant)
 ADD_EXAMPLE(determinant2)
 ADD_EXAMPLE(qr)
+ADD_EXAMPLE(pivoting_qr)
 ADD_EXAMPLE(qr_space)
 ADD_EXAMPLE(cholesky)
 ADD_EXAMPLE(chol)

example/linalg/example_pivoting_qr.f90

@@ -0,0 +1,16 @@
+program example_pivoting_qr
+   use stdlib_linalg, only: qr
+   implicit none
+   real :: A(104, 32), Q(104, 32), R(32, 32)
+   integer :: pivots(32)
+
+   ! Create a random matrix
+   call random_number(A)
+
+   ! Compute its QR factorization (reduced)
+   call qr(A, Q, R, pivots)
+
+   ! Test factorization: Q*R = A
+   print *, maxval(abs(matmul(Q, R) - A(:, pivots)))
+
+end program example_pivoting_qr