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Lapack95 example 2

This example shows the use of SYTRF method.

program main
use easifemBase
implicit none
declare variables
real(dfp), allocatable :: mat(:, :), mat0(:,:)
integer(i4b), allocatable :: ipiv(:)
integer(i4b) :: info
character(len=1) :: uplo
make matrix
allocate(mat(3,3), mat0(3,3), ipiv(3))
mat0(1, :) = [2, -1, 3]
mat0(2, :) = [0, 2, 0]
mat0(3, :) = [0, 0, 1]

Test without extra arguments.

test-1
uplo = "U"
mat = mat0
CALL SYTRF(A=mat, UPLO=uplo)
CALL Display(mat, "mat = ")
results
            mat =
----------------------------
-5.00000   1.00000   1.50000
 0.00000   1.50000  -0.50000
 0.00000   0.00000   2.00000
test-2
mat = mat0
CALL SYTRF(A=mat, UPLO=uplo, IPIV=ipiv, info=info)
CALL Display( mat, "mat = " )
CALL Display( ipiv, "ipiv = " )
CALL Display( info, "info = " )
results
mat =
----------------------------
-5.00000   1.00000   1.50000
 0.00000   1.50000  -0.50000
 0.00000   0.00000   2.00000
ipiv =
-------
   1
   2
   1
info = 0
test-3
call reallocate(mat0, 4,4)
call reallocate(ipiv, 4)

mat0 = RESHAPE( &
    & [9.56982809,  3.30527253,  7.30953613,  8.18680201, 3.30527253,   &
    & 8.38597454, 10.68872278, 10.01187194, 7.30953613, &
    & 10.68872278, 17.30316194, 14.31931041, 8.18680201, &
    & 10.01187194, 14.31931041, 14.12868642], &
    & [4,4] )

mat0 = TRANSPOSE(mat0)

mat = mat0
CALL SYTRF(A=mat, UPLO=uplo, IPIV=ipiv, info=info)
CALL Display( mat0, "mat0 = " )
CALL Display( mat, "mat = " )
CALL Display( ipiv, "ipiv = " )
CALL Display( info, "info = " )
cleanup
end program main