Discrepancy in negation of a > statement

[jlk9]

Running this script produces an error in the numerical values between Oceananigans models with and without reactant. This seems to be due to an error in how negations of > and >= operators are handled. If you look at lines 290 - 307:

    active_nodes = (!(grid.underlying_grid.z.cᵃᵃᶜ[k] ≤ grid.immersed_boundary.bottom_height[i, j-1, 1]) # NEGATING THIS ELIMINATES ERROR, NEED TO INVESTIGATE
                  & !(grid.underlying_grid.z.cᵃᵃᶜ[k] ≤ grid.immersed_boundary.bottom_height[i-1, j-1, 1])
                  & !(grid.underlying_grid.z.cᵃᵃᶜ[k] ≤ grid.immersed_boundary.bottom_height[i+1, j-1, 1])
                  & (j > 1)
                  & (j < (grid.Ny+2))
                  & (k > 0)
                  & (k < grid.Nz+1))
    
    #=
    # Works:
    active_nodes = ((grid.underlying_grid.z.cᵃᵃᶜ[k] > grid.immersed_boundary.bottom_height[i, j-1, 1])
                  & (grid.underlying_grid.z.cᵃᵃᶜ[k] > grid.immersed_boundary.bottom_height[i-1, j-1, 1])
                  & (grid.underlying_grid.z.cᵃᵃᶜ[k] > grid.immersed_boundary.bottom_height[i+1, j-1, 1])
                  & (j > 1)
                  & (j < (grid.Ny+2))
                  & (k > 0)
                  & (k < grid.Nz+1))
    =#

Logically these blocks should be equivalent (!(a ≤ b) == a > b, but they produce different values for the Reactant model.

@wsmoses

[jlk9]

I attempted a fix through Oceananigans, in this branch (jlk9/not-peripheral-node-extension). This would not apply for the most reduced version of this error but for an older commit that still features not_peripheral_node, such as commit c05ddb2b6418d0be624a69dc6e8cfd3fb231969a.

Normally not_peripheral_node = !peripheral_node, which ultimately reduces to a statement !(a ≤ b). I added a new method for not_peripheral_node in the Reactant extension that bypasses this and simply checks for a > b, but it still produces the error.

Even if it is modified to work, it requires extending not just not_peripheral_node but several helper functions as well - a fix within Reactant would be more ideal.

[jlk9]

The above script has been reduced to the point where it no longer uses Oceananigans - it's simple showing !(a ≤ b) doesn't apply correctly on Reactant.