Finds the smallest integers for creating a new BLACS context.
base.minctxt(after = 0)ignores all values below this integer as possibilities
Returns the minimum value.
For advanced users only.
Returns the smallest integer which could become a new BLACS context value.
For example, if contexts 0, 1, and 2 are taken, and after=0, then the
function returns 3. If 0, 1, 2, and 5 are taken, the function returns 3 if
after=0, but returns 6 if after=4.
The function is useful when a transitory grid is needed, such as for reading in data onto a subset of processors before distributing out to the full grid.