| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| class(base_backend_t) | :: | self | ||||
| class(field_t), | intent(inout) | :: | u_ | |||
| class(field_t), | intent(in) | :: | u | |||
| integer, | intent(in) | :: | direction | 
reorder subroutines are straightforward, they rearrange data into our specialist data structure so that regardless of the direction tridiagonal systems are solved efficiently and fast.