Compile EinExprs to native code or IR

[mofeing]

EinExpr can be seen as symbolic expressions that represent linear operations expressible using the Einstein summation notation.

The user can walk through the tree and execute the appropriate methods by identifying the array types with almost no overhead.

But what if we could compile directly these symbolic trees into native code? Could we gain something?

Things to check:

• Link Backward Automatic Differentiation with compilation
• Link it with batched contraction
• Multiple Level Intermediate Representation (MLIR)