Hash-Based Random-Integer operator[] Insert Timing Test

Description

This test inserts a number of values with uniform i.i.d. integer keys into a container, using operator[]. It measures the average time for operator[] as a function of the number of values inserted.

(The test was executed with hash_random_int_subscript_insert_timing_test 200 200 2100)

Purpose

The test primarily checks the effect of different underlying hash-tables (see Design::Associative Containers::Associative Containers::Hash-Based Containers).

Results

Figures NCCG, NCCM, and NCCL show the results for the native and collision-chaining types in g++, MSVC++, and local, respectively; Figures NGPG, NGPM, and NGPL show the results for the native and probing types in g++, msvc++, and local respectively; Figures CCGPG, CCGPM, and CCGPL compare the results for the collision-chaining and probing types of pb_ds only, in g++, MSVC++, and local respectively.

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NCCG: Native and collision-chaining hash random int insert timing test using operator - g++

In the above figure, the names in the legends have the following meaning:

  1. cc_hash_mod_prime_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  2. n_hash_map_ncah- std::tr1::unordered_map with cache_hash_code = false
  3. cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  4. cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/1
  5. cc_hash_mask_exp_nea_lc_1div8_1div1_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/1
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NCCM: Native and collision-chaining hash random int insert timing test using operator - msvc++

In the above figure, the names in the legends have the following meaning:

  1. n_hash_map_ncah- stdext::hash_map
  2. cc_hash_mod_prime_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  3. cc_hash_mod_prime_nea_lc_1div8_1div1_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/1
  4. cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  5. cc_hash_mask_exp_nea_lc_1div8_1div1_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/1
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NCCL: Native and collision-chaining hash random int insert timing test using operator - local
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NGPG: Native and probing hash random int insert timing test using operator - g++

In the above figure, the names in the legends have the following meaning:

  1. gp_hash_mod_quadp_prime_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = quadratic_probe_fn
  2. n_hash_map_ncah- std::tr1::unordered_map with cache_hash_code = false
  3. gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = linear_probe_fn
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NGPM: Native and probing hash random int insert timing test using operator - msvc++

In the above figure, the names in the legends have the following meaning:

  1. n_hash_map_ncah- stdext::hash_map
  2. gp_hash_mod_quadp_prime_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = quadratic_probe_fn
  3. gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = linear_probe_fn
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NGPL: Native and probing hash random int insert timing test using operator - local
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CCGPG: Collision-chaining and probing hash random int insert timing test using operator - g++

In the above figure, the names in the legends have the following meaning:

  1. gp_hash_mod_quadp_prime_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = quadratic_probe_fn
  2. cc_hash_mod_prime_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  3. cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  4. gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = linear_probe_fn
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CCGPM: Collision-chaining and probing hash random int insert timing test using operator - msvc++

In the above figure, the names in the legends have the following meaning:

  1. cc_hash_mod_prime_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  2. cc_hash_mask_exp_nea_lc_1div8_1div2_nsth_map- cc_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , and Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2
  3. gp_hash_mod_quadp_prime_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mod_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_prime_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = quadratic_probe_fn
  4. gp_hash_mask_linp_exp_nea_lc_1div8_1div2_nsth_map- gp_hash_table with Comb_Hash_Fn = direct_mask_range_hashing , Resize_Policy = hash_standard_resize_policy with Size_Policy = hash_exponential_size_policy , and Trigger_Policy = hash_load_check_resize_trigger with αmin = 1/8 and αmax = 1/2, and Probe_Fn = linear_probe_fn
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CCGPL: Collision-chaining and probing hash random int insert timing test using operator - local

Observations

In this setting, as in Hash-Based Text find Find Timing Test and Hash-Based Random-Integer find Find Timing Test , the choice of underlying hash-table underlying hash-table (see Design::Associative Containers::Hash-Based Containers ) affects performance most, then the range-hashing scheme (See Design::Associative Containers::Hash-Based Containers::Hash Policies ), and, only finally, other policies.

There are some differences, however:

  1. In this setting, probing tables function sometimes more efficiently than collision-chaining tables (see Figures CCGPG and CCGPM ). This is explained shortly.
  2. The performance graphs have a "saw-tooth" shape. The average insert time rises and falls. As values are inserted into the container, the load factor grows larger. Eventually, a resize occurs. The reallocations and rehashing are relatively expensive. After this, the load factor is smaller than before.

Collision-chaining containers use indirection for greater flexibility; probing containers store values contiguously, in an array (see Figure Motivation::Different underlying data structures A and B, respectively). It follows that for simple data types, probing containers access their allocator less frequently than collision-chaining containers, (although they still have less efficient probing sequences). This explains why some probing containers fare better than collision-chaining containers in this case.

Within each type of hash-table, the range-hashing scheme affects performance more than other policies. This is similar to the situation in Hash-Based Text find Find Timing Test and Hash-Based Random-Integer find Find Timing Test. Unsurprisingly, however, containers with lower alphamax perform worse in this case, since more re-hashes are performed.

Observations::Hash-Based Container Types summarizes some observations on hash-based containers; Observations::Hash-Based Containers' Policies summarizes some observations on hash-based containers' policies.