[Refactor] MemoryMappedTensor

[vmoens]

This PR refactors MemmapTensor to a new Tensor-based class, MemoryMappedTensor.
This should be considerably faster.
MemmapTensor is kept within the library as a separate class which will raise a deprecation warning when created.

This change is bc-breaking in a subtle manner:
when creating a memmap tensordict, the backend will now be MemoryMappedTensor.
When indexed, MemoryMappedTensor will return an object from the same class only if the storage of the indexed object is the same as the original one (where MemmapTensor was always returning a MemmapTensor with a lazy index).
This in turn means that indexing a tensordict with, say, a tensor will now return a tensordict with tensors and not memmap valued tensors. For slices and other indexes that do not modify the storage, nothing will change.

[github-actions]

$\color{#D29922}\textsf{\Large⚠\kern{0.2cm}\normalsize Warning}$ Result of CPU Benchmark Tests

Total Benchmarks: 105. Improved: $\large\color{#35bf28}14$. Worsened: $\large\color{#d91a1a}3$.

Expand to view detailed results

Name	Max	Mean	Ops	Ops on Repo HEAD	Change
test_plain_set_nested	30.8990μs	19.8620μs	50.3475 KOps/s	49.5428 KOps/s	$\color{#35bf28}+1.62\%$
test_plain_set_stack_nested	0.2031ms	0.1816ms	5.5068 KOps/s	5.3938 KOps/s	$\color{#35bf28}+2.09\%$
test_plain_set_nested_inplace	49.1990μs	23.6753μs	42.2380 KOps/s	42.2575 KOps/s	$\color{#d91a1a}-0.05\%$
test_plain_set_stack_nested_inplace	0.2499ms	0.2213ms	4.5179 KOps/s	4.5202 KOps/s	$\color{#d91a1a}-0.05\%$
test_items	0.1365ms	3.0734μs	325.3702 KOps/s	329.0883 KOps/s	$\color{#d91a1a}-1.13\%$
test_items_nested	0.4348ms	0.3967ms	2.5211 KOps/s	2.6157 KOps/s	$\color{#d91a1a}-3.62\%$
test_items_nested_locked	0.4206ms	0.3966ms	2.5212 KOps/s	2.7483 KOps/s	$\textbf{\color{#d91a1a}-8.26\%}$
test_items_nested_leaf	1.2236ms	0.2370ms	4.2191 KOps/s	4.5363 KOps/s	$\textbf{\color{#d91a1a}-6.99\%}$
test_items_stack_nested	1.8610ms	1.7989ms	555.8982 Ops/s	548.8150 Ops/s	$\color{#35bf28}+1.29\%$
test_items_stack_nested_leaf	1.6357ms	1.6015ms	624.4084 Ops/s	605.7387 Ops/s	$\color{#35bf28}+3.08\%$
test_items_stack_nested_locked	1.0711ms	0.9864ms	1.0138 KOps/s	1.0435 KOps/s	$\color{#d91a1a}-2.85\%$
test_keys	37.8990μs	4.6576μs	214.7023 KOps/s	204.3353 KOps/s	$\textbf{\color{#35bf28}+5.07\%}$
test_keys_nested	1.5733ms	0.1737ms	5.7584 KOps/s	5.3897 KOps/s	$\textbf{\color{#35bf28}+6.84\%}$
test_keys_nested_locked	0.2180ms	0.1727ms	5.7888 KOps/s	5.7669 KOps/s	$\color{#35bf28}+0.38\%$
test_keys_nested_leaf	1.5901ms	0.1703ms	5.8728 KOps/s	5.8245 KOps/s	$\color{#35bf28}+0.83\%$
test_keys_stack_nested	1.6947ms	1.6046ms	623.1981 Ops/s	597.0795 Ops/s	$\color{#35bf28}+4.37\%$
test_keys_stack_nested_leaf	1.7368ms	1.6032ms	623.7371 Ops/s	597.8020 Ops/s	$\color{#35bf28}+4.34\%$
test_keys_stack_nested_locked	1.0023ms	0.7785ms	1.2846 KOps/s	1.2710 KOps/s	$\color{#35bf28}+1.07\%$
test_values	20.1000μs	1.3236μs	755.5340 KOps/s	767.0575 KOps/s	$\color{#d91a1a}-1.50\%$
test_values_nested	88.4990μs	64.4041μs	15.5270 KOps/s	14.8769 KOps/s	$\color{#35bf28}+4.37\%$
test_values_nested_locked	85.7000μs	64.8049μs	15.4309 KOps/s	14.8543 KOps/s	$\color{#35bf28}+3.88\%$
test_values_nested_leaf	77.4990μs	56.3876μs	17.7344 KOps/s	16.7470 KOps/s	$\textbf{\color{#35bf28}+5.90\%}$
test_values_stack_nested	1.4905ms	1.4025ms	712.9937 Ops/s	654.9123 Ops/s	$\textbf{\color{#35bf28}+8.87\%}$
test_values_stack_nested_leaf	1.4241ms	1.3926ms	718.0730 Ops/s	680.9733 Ops/s	$\textbf{\color{#35bf28}+5.45\%}$
test_values_stack_nested_locked	0.7160ms	0.6306ms	1.5858 KOps/s	1.5678 KOps/s	$\color{#35bf28}+1.15\%$
test_membership	54.3000μs	1.8802μs	531.8626 KOps/s	496.1601 KOps/s	$\textbf{\color{#35bf28}+7.20\%}$
test_membership_nested	25.4000μs	3.7995μs	263.1918 KOps/s	260.2904 KOps/s	$\color{#35bf28}+1.11\%$
test_membership_nested_leaf	24.3000μs	3.7869μs	264.0692 KOps/s	259.8244 KOps/s	$\color{#35bf28}+1.63\%$
test_membership_stacked_nested	40.5000μs	14.9136μs	67.0530 KOps/s	61.5273 KOps/s	$\textbf{\color{#35bf28}+8.98\%}$
test_membership_stacked_nested_leaf	36.1000μs	14.8780μs	67.2135 KOps/s	61.2329 KOps/s	$\textbf{\color{#35bf28}+9.77\%}$
test_membership_nested_last	31.1000μs	7.6781μs	130.2397 KOps/s	127.9960 KOps/s	$\color{#35bf28}+1.75\%$
test_membership_nested_leaf_last	28.2000μs	7.6658μs	130.4503 KOps/s	128.1257 KOps/s	$\color{#35bf28}+1.81\%$
test_membership_stacked_nested_last	0.2507ms	0.2271ms	4.4026 KOps/s	4.3793 KOps/s	$\color{#35bf28}+0.53\%$
test_membership_stacked_nested_leaf_last	42.4000μs	17.1021μs	58.4723 KOps/s	54.0353 KOps/s	$\textbf{\color{#35bf28}+8.21\%}$
test_nested_getleaf	38.6000μs	15.7113μs	63.6486 KOps/s	63.7431 KOps/s	$\color{#d91a1a}-0.15\%$
test_nested_get	37.8000μs	14.9417μs	66.9267 KOps/s	66.7999 KOps/s	$\color{#35bf28}+0.19\%$
test_stacked_getleaf	0.8172ms	0.7248ms	1.3797 KOps/s	1.3307 KOps/s	$\color{#35bf28}+3.69\%$
test_stacked_get	3.0511ms	0.7057ms	1.4171 KOps/s	1.3817 KOps/s	$\color{#35bf28}+2.56\%$
test_nested_getitemleaf	0.1785ms	15.7278μs	63.5819 KOps/s	63.0654 KOps/s	$\color{#35bf28}+0.82\%$
test_nested_getitem	39.3000μs	14.9090μs	67.0738 KOps/s	66.7099 KOps/s	$\color{#35bf28}+0.55\%$
test_stacked_getitemleaf	0.8108ms	0.7239ms	1.3813 KOps/s	1.3315 KOps/s	$\color{#35bf28}+3.75\%$
test_stacked_getitem	0.7621ms	0.6932ms	1.4427 KOps/s	1.3894 KOps/s	$\color{#35bf28}+3.84\%$
test_lock_nested	56.2092ms	1.1674ms	856.5861 Ops/s	898.2715 Ops/s	$\color{#d91a1a}-4.64\%$
test_lock_stack_nested	75.9773ms	15.4593ms	64.6858 Ops/s	64.7886 Ops/s	$\color{#d91a1a}-0.16\%$
test_unlock_nested	52.2380ms	1.1721ms	853.1495 Ops/s	857.0762 Ops/s	$\color{#d91a1a}-0.46\%$
test_unlock_stack_nested	73.9057ms	15.9683ms	62.6241 Ops/s	62.5045 Ops/s	$\color{#35bf28}+0.19\%$
test_flatten_speed	0.9157ms	0.8464ms	1.1814 KOps/s	1.1403 KOps/s	$\color{#35bf28}+3.60\%$
test_unflatten_speed	1.5477ms	1.4581ms	685.8198 Ops/s	679.7259 Ops/s	$\color{#35bf28}+0.90\%$
test_common_ops	3.0637ms	0.7620ms	1.3124 KOps/s	1.2933 KOps/s	$\color{#35bf28}+1.47\%$
test_creation	58.7990μs	3.0033μs	332.9638 KOps/s	338.7230 KOps/s	$\color{#d91a1a}-1.70\%$
test_creation_empty	30.4000μs	9.4507μs	105.8122 KOps/s	103.1488 KOps/s	$\color{#35bf28}+2.58\%$
test_creation_nested_1	38.2000μs	14.0648μs	71.0993 KOps/s	68.7925 KOps/s	$\color{#35bf28}+3.35\%$
test_creation_nested_2	77.3990μs	17.5322μs	57.0378 KOps/s	56.2737 KOps/s	$\color{#35bf28}+1.36\%$
test_clone	62.3000μs	14.7359μs	67.8616 KOps/s	67.1602 KOps/s	$\color{#35bf28}+1.04\%$
test_getitem[int]	42.6000μs	17.6245μs	56.7392 KOps/s	56.5610 KOps/s	$\color{#35bf28}+0.32\%$
test_getitem[slice_int]	80.4990μs	37.9480μs	26.3518 KOps/s	26.8056 KOps/s	$\color{#d91a1a}-1.69\%$
test_getitem[range]	0.1490ms	61.5293μs	16.2524 KOps/s	16.4511 KOps/s	$\color{#d91a1a}-1.21\%$
test_getitem[tuple]	65.1990μs	31.9996μs	31.2504 KOps/s	31.3216 KOps/s	$\color{#d91a1a}-0.23\%$
test_getitem[list]	0.3077ms	56.6766μs	17.6440 KOps/s	17.7100 KOps/s	$\color{#d91a1a}-0.37\%$
test_setitem_dim[int]	42.9000μs	32.4730μs	30.7948 KOps/s	30.3910 KOps/s	$\color{#35bf28}+1.33\%$
test_setitem_dim[slice_int]	69.7000μs	58.6333μs	17.0552 KOps/s	17.0206 KOps/s	$\color{#35bf28}+0.20\%$
test_setitem_dim[range]	94.9000μs	77.5515μs	12.8947 KOps/s	12.8177 KOps/s	$\color{#35bf28}+0.60\%$
test_setitem_dim[tuple]	64.6000μs	49.5589μs	20.1780 KOps/s	20.4398 KOps/s	$\color{#d91a1a}-1.28\%$
test_setitem	97.1990μs	19.5600μs	51.1247 KOps/s	50.2497 KOps/s	$\color{#35bf28}+1.74\%$
test_set	95.0000μs	18.9636μs	52.7326 KOps/s	51.7950 KOps/s	$\color{#35bf28}+1.81\%$
test_set_shared	2.5620ms	0.1613ms	6.1990 KOps/s	6.2644 KOps/s	$\color{#d91a1a}-1.04\%$
test_update	0.1102ms	24.5620μs	40.7133 KOps/s	40.2141 KOps/s	$\color{#35bf28}+1.24\%$
test_update_nested	0.1092ms	34.5724μs	28.9248 KOps/s	28.8636 KOps/s	$\color{#35bf28}+0.21\%$
test_set_nested	86.1000μs	20.6430μs	48.4427 KOps/s	47.6956 KOps/s	$\color{#35bf28}+1.57\%$
test_set_nested_new	87.5990μs	28.1364μs	35.5411 KOps/s	34.5961 KOps/s	$\color{#35bf28}+2.73\%$
test_select	0.1231ms	59.4096μs	16.8323 KOps/s	17.0197 KOps/s	$\color{#d91a1a}-1.10\%$
test_unbind_speed	0.4211ms	0.3689ms	2.7106 KOps/s	2.5821 KOps/s	$\color{#35bf28}+4.98\%$
test_unbind_speed_stack0	59.6449ms	5.2735ms	189.6275 Ops/s	180.9227 Ops/s	$\color{#35bf28}+4.81\%$
test_unbind_speed_stack1	13.7998μs	0.9610μs	1.0406 MOps/s	872.9610 KOps/s	$\textbf{\color{#35bf28}+19.21\%}$
test_creation[device0]	2.0331ms	0.3531ms	2.8324 KOps/s	2.9005 KOps/s	$\color{#d91a1a}-2.35\%$
test_creation_from_tensor	57.4586ms	0.4327ms	2.3113 KOps/s	2.6088 KOps/s	$\textbf{\color{#d91a1a}-11.40\%}$
test_add_one[memmap_tensor0]	0.1614ms	30.4083μs	32.8858 KOps/s	32.3060 KOps/s	$\color{#35bf28}+1.79\%$
test_contiguous[memmap_tensor0]	30.9000μs	8.3491μs	119.7740 KOps/s	115.7872 KOps/s	$\color{#35bf28}+3.44\%$
test_stack[memmap_tensor0]	62.1990μs	25.6047μs	39.0553 KOps/s	38.7801 KOps/s	$\color{#35bf28}+0.71\%$
test_memmaptd_index	0.3390ms	0.2737ms	3.6534 KOps/s	3.4439 KOps/s	$\textbf{\color{#35bf28}+6.08\%}$
test_memmaptd_index_astensor	0.4017ms	0.3438ms	2.9085 KOps/s	920.5795 Ops/s	$\textbf{\color{#35bf28}+215.94\%}$
test_memmaptd_index_op	0.7338ms	0.6646ms	1.5047 KOps/s	426.7540 Ops/s	$\textbf{\color{#35bf28}+252.58\%}$
test_reshape_pytree	0.1094ms	31.8367μs	31.4103 KOps/s	31.0341 KOps/s	$\color{#35bf28}+1.21\%$
test_reshape_td	54.8000μs	28.1369μs	35.5406 KOps/s	34.6788 KOps/s	$\color{#35bf28}+2.49\%$
test_view_pytree	77.8000μs	31.2610μs	31.9887 KOps/s	31.6496 KOps/s	$\color{#35bf28}+1.07\%$
test_view_td	17.0000μs	5.5344μs	180.6868 KOps/s	182.5779 KOps/s	$\color{#d91a1a}-1.04\%$
test_unbind_pytree	96.2990μs	37.3767μs	26.7547 KOps/s	26.8546 KOps/s	$\color{#d91a1a}-0.37\%$
test_unbind_td	98.6990μs	53.4983μs	18.6922 KOps/s	18.6957 KOps/s	$\color{#d91a1a}-0.02\%$
test_split_pytree	62.9000μs	36.7675μs	27.1979 KOps/s	27.4156 KOps/s	$\color{#d91a1a}-0.79\%$
test_split_td	0.1783ms	96.6925μs	10.3421 KOps/s	10.2860 KOps/s	$\color{#35bf28}+0.55\%$
test_add_pytree	78.8000μs	45.0505μs	22.1973 KOps/s	22.2857 KOps/s	$\color{#d91a1a}-0.40\%$
test_add_td	81.0000μs	55.9716μs	17.8662 KOps/s	17.7740 KOps/s	$\color{#35bf28}+0.52\%$
test_distributed	54.0000μs	8.2250μs	121.5802 KOps/s	122.6607 KOps/s	$\color{#d91a1a}-0.88\%$
test_tdmodule	0.1141ms	24.4962μs	40.8227 KOps/s	40.2242 KOps/s	$\color{#35bf28}+1.49\%$
test_tdmodule_dispatch	0.2154ms	44.5125μs	22.4656 KOps/s	22.6101 KOps/s	$\color{#d91a1a}-0.64\%$
test_tdseq	0.1390ms	26.4022μs	37.8757 KOps/s	37.8803 KOps/s	$\color{#d91a1a}-0.01\%$
test_tdseq_dispatch	0.5242ms	46.5668μs	21.4745 KOps/s	21.6141 KOps/s	$\color{#d91a1a}-0.65\%$
test_instantiation_functorch	1.6548ms	1.5387ms	649.8968 Ops/s	648.0128 Ops/s	$\color{#35bf28}+0.29\%$
test_instantiation_td	1.8319ms	1.2300ms	813.0208 Ops/s	756.6224 Ops/s	$\textbf{\color{#35bf28}+7.45\%}$
test_exec_functorch	0.2683ms	0.1860ms	5.3768 KOps/s	5.4536 KOps/s	$\color{#d91a1a}-1.41\%$
test_exec_td	0.2141ms	0.1773ms	5.6397 KOps/s	5.7691 KOps/s	$\color{#d91a1a}-2.24\%$
test_vmap_mlp_speed[True-True]	6.8421ms	0.9894ms	1.0107 KOps/s	1.0174 KOps/s	$\color{#d91a1a}-0.67\%$
test_vmap_mlp_speed[True-False]	6.3454ms	0.5304ms	1.8853 KOps/s	1.9025 KOps/s	$\color{#d91a1a}-0.91\%$
test_vmap_mlp_speed[False-True]	1.1983ms	0.8495ms	1.1772 KOps/s	1.1630 KOps/s	$\color{#35bf28}+1.22\%$
test_vmap_mlp_speed[False-False]	6.2969ms	0.4366ms	2.2906 KOps/s	2.3035 KOps/s	$\color{#d91a1a}-0.56\%$