Memoization

[hypercubestart]

working on #7,

• memoize interpreter
• add benchmark test for subset of mobilenet
• fix softmax with large numbers causing NAN
  (https://stackoverflow.com/questions/54880369/implementation-of-softmax-function-returns-nan-for-high-inputs)

test_name	original	memo
access_cartesian_product	28,724 ns/iter (+/- 3,391)	30,334 ns/iter (+/- 3,681)
access_concatenate_0	1,341 ns/iter (+/- 105)	3,336 ns/iter (+/- 305)
access_concatenate_1	1,754 ns/iter (+/- 147)	3,690 ns/iter (+/- 1,929)
access_pad	2,294 ns/iter (+/- 229)	3,094 ns/iter (+/- 846)
access_pair_0	1,506 ns/iter (+/- 124)	3,455 ns/iter (+/- 244)
access_pair_1	2,196 ns/iter (+/- 198)	4,131 ns/iter (+/- 221)
access_pair_2	2,126 ns/iter (+/- 113)	4,056 ns/iter (+/- 235)
access_slice_0	861 ns/iter (+/- 93)	2,031 ns/iter (+/- 204)
access_slice_1	915 ns/iter (+/- 514)	1,987 ns/iter (+/- 104)
access_slice_2	1,138 ns/iter (+/- 328)	2,243 ns/iter (+/- 143)
access_windows	21,145 ns/iter (+/- 2,394)	22,899 ns/iter (+/- 2,094)
compute_dot_product_0	2,126 ns/iter (+/- 605)	3,115 ns/iter (+/- 167)
compute_dot_product_1	3,288 ns/iter (+/- 382)	4,318 ns/iter (+/- 305)
compute_elementwise_add_0	1,199 ns/iter (+/- 80)	2,152 ns/iter (+/- 655)
compute_elementwise_mul_0	1,219 ns/iter (+/- 144)	2,132 ns/iter (+/- 228)
compute_reduce_sum_0	1,985 ns/iter (+/- 218)	3,019 ns/iter (+/- 244)
compute_reduce_sum_1	1,203 ns/iter (+/- 274)	2,175 ns/iter (+/- 283)
compute_reduce_sum_2	1,736 ns/iter (+/- 174)	2,709 ns/iter (+/- 477)
compute_reduce_sum_3	1,146 ns/iter (+/- 74)	2,071 ns/iter (+/- 150)
compute_relu_0	610 ns/iter (+/- 33)	1,518 ns/iter (+/- 119)
compute_relu_1	643 ns/iter (+/- 52)	1,526 ns/iter (+/- 108)
mobilenet_shallow	stack overflow	114,933,006 ns/iter (+/- 2,813,140)

[hypercubestart]

on hold for now...because of difficulty of getting lifetimes to work out. Ideally, we could use ArrayViews that reference owned arrays already in the hashmap, but Rust doesn't like this.

• CowArray (doesn't work because view variant has lifetimes, so if we insert array back into hashmap, we end up borrowing the hashmap mutably + immutably)
• Wrap with RC and see if that works (same error as cowarray)
• ArcArray (shared references, but same benchmarks as naive copying)
• Try out data structure idea (see whether there’s a better datatype for what we’re trying to do, better than hashmap, i.e an insert-only datastructure that guarantees that lifetimes do not change when we insert) (not quite sure if this is expressible in rust?)
• Adding a enum wrapper over ndarrray that holds owned data or views/shared data ArrayBase<MyCustomRepr…, >
• unsafe