[Enhancement] Compiling time is remained to be optimized. about cl-waffe2

[hikettei]

On compiling, the costs of (!sin x) and (!sin (!sin (!sin x))) should be the same because all tensors used here, has the same shape, same views.

[hikettei]

Goal: 3 Layers MLP's compiling time of forward and backward << 5sec.

Compiling time with cache.lisp will be approximated as:

O((the number of kernel types used in nodes))

while without cache.lisp:

O((the number of operation))

[hikettei]

The latest pull request #10 solved this issue, however, there still remained to be optimized of compiling time, especially in backward compiling...

[hikettei]

(Compiling MLP Time) is now <<0.5s