Effect:

If msk was non-null, the effect is like executing the conditional assignment

   if(msk [  ])

    dst [   [  ], ...,
                 [  ]] =

                         src [  ]

for every tuple of global subscripts of the source array. These assignments are executed in an undefined order. If msk is a null pointer, the assignment is unconditional. Here denotest the rth subscript array.