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Clarify the documentation for PermuteDimensions

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PiperOrigin-RevId: 316616603
Change-Id: Iccfbd986276688bdc25b6757cdee6806f0b587d6
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A. Unique TensorFlower 2020-06-15 22:24:35 -07:00 committed by TensorFlower Gardener
parent 7ee9571a8e
commit e74010b4e8
1 changed files with 8 additions and 7 deletions
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15
tensorflow/compiler/xla/shape_util.cc
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@ -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' =>