Is there Fortran subroutine in LAPACK/BLAS or somewhere else to calculate LDL decomposition?

Check out the SSPTRF function from LAPACK: Purpose SSPTRF computes the factorization of a real symmetric matrix A stored in packed format using the Bunch-Kaufman diagonal pivoting method: A = U*D*U**T or A = L*D*L**T where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and D is symmetric and block diagonal with 1-by-1 and 2-by-2 diagonal blocks Also, Golub and van Loan's "Matrix Computations" book gives an algorithm for doing the decomposition. In my third edition, it's on page 138, Section 4.1.2 "Symmetry and the LDL^T Factorization.

Check out the SSPTRF function from LAPACK: Purpose ======= SSPTRF computes the factorization of a real symmetric matrix A stored in packed format using the Bunch-Kaufman diagonal pivoting method: A = U*D*U**T or A = L*D*L**T where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and D is symmetric and block diagonal with 1-by-1 and 2-by-2 diagonal blocks. Also, Golub and van Loan's "Matrix Computations" book gives an algorithm for doing the decomposition. In my third edition, it's on page 138, Section 4.1.2 "Symmetry and the LDL^T Factorization".

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