message: Clarify the documentation for PermuteDimensions
diff: @@ -968,17 +968,18 @@ Status ForEachMutableSubshapeHelper(
  // `shape`'s list of dimensions is isomorphic to the identity I.
  //
  // Let `shape`'s layout be L. A layout is a permutation which maps a
  - // minor-to-major physical layout to the order of a shape's logical dims.
  - // Therefore inverse of a layout maps from logical to physical dims, and so
  - // the physical layout of I is simply L'.I = L', where L' is the inverse of L.
  + // minor-to-major physical dimension ordering to a shape's logical dimension
  + // ordering. Therefore the inverse of a layout maps from logical to physical
  + // dims, and so the physical ordering of I is simply L'.I = L', where L' is
  + // the inverse of L.
  //
  // Let the argument `permutation` be P. This is a permutation over `shape`'s
  // dimensions, so our return value will be a shape with dims P.I = P. Our
  - // goal is to construct a layout permutation L* that we can apply to P such
  - // that the physical dimension ordering of the returned shape is the same
  - // as that of the original shape, namely L'.
  + // goal is to construct a layout permutation L* for this shape. The physical
  + // dimension ordering of this returned shape must be the same as that of the
  + // original shape, namely L'.
  //
  - // Our returned shape has dims P and layout L*, so its in-memory layout is
  + // Our returned shape has dims P and layout L*, so its in-memory ordering is
  // L*'.P. Setting this equal to L' and solving for L*, we get:
  //
  // L*'.P = L' =>
  