Performance comparison of three different implementations of dynamic_cast in C++
I intended to center my new software design around dynamic_cast when I found repeated mention of allegedly poor performance of it, as well as outright exclamations that one’s software design turns ‘poor’ the second one introduces it it!
I took the warnings seriously at first but wanted to know more. Starting to dig deeper, I found only assertions which are either not backed up at all, or assertions based on invalid comparisons, for example comparing the run-time feature dynamic_cast with the compile-time feature reinterpret_cast. Well sure, compared to a zero-cost operation, everything is infinitely slower!
But these circumstances are well-known:
The field of performance is littered with myth and bogus folklore.
In trying to decide if my software design is indeed ‘allowed’ to center around dynamic casting, I was in need of good measurements. So, I followed C++ Core Guideline Per.6: Don’t make claims about performance without measurements and wrote a benchmark program to compare 3 different implementation of dynamic_cast. It compares:
- The C++ built-in
dynamic_castoperator, kcl_dynamic_cast(2019. See Blog post, and Github repo),priori_cast(2013. See Blog post, and Github repo). This is an implementation of the method presented in the paper Fast dynamic casting [Gibbs & Stroustrup, 2006].
Method
Writing a reasonable benchmark program was indeed harder than I anticipated, as predicted:
Getting good performance measurements can be hard and require specialized tools.
One of the hard parts was to choose a realistic unit of work which can serve as a comparable base-line. The emphasis here is on “realistic”; for example, I don’t think that repeatedly doing the same type of cast on the same object is very realistic.
This unit of work should also be as small as possible to maximize the performance impact of dynamic casting:
- Do a
dynamic_cast<Base*>on an object inheriting fromBase. This has zero runtime cost because the cast will always succeed; the compiler can optimize this away, and it is equivalent to astatic_cast<Base*>. - If the cast is successful, increment a running total; if not, increment another running total. It is important to spend the same number of cycles in both branches, to not skew the view at the latency of the cast.
This unit of work is done repeatedly by iterating over 2 million individual objects (which are instances of class Base or of its sub-types) stored in a std::vector<std::shared_ptr<Base>> . The objects are in contiguous memory, but can be aligned, or shuffled; on modern hardware architectures, this makes a big difference due to cache prefetching.
This base-line is then compared to cases were only one parameter is varied: the target class of dynamic_cast.
Benchmark program
The program uses 3 different class hierarchies to cover the most typical casting scenarios: Deep, shallow, and balanced.
Deep hierarchy:
A ← B ← C ← D ← E ← F ← G ← H
Shallow hierarchy:
A ← B
A ← C
A ← D
A ← E
A ← F
A ← G
A ← H
Balanced hierarchy:
A ← B
A ← E
B ← C
B ← D
E ← F
E ← G
E ← H
I made the source code of the benchmark program available.
There may be mistakes in the program. If you discover one, please leave a comment below or contribute a merge request.
The output of an example run on the program can be found below.
Findings
If anything is proven here, then this:
Modern hardware and optimizers defy naive assumptions; even experts are regularly surprised.
I tried to extract out of the program output below general observations; this is somewhat possible, but there are exceptions, and a few odd items.
- It is clear that in all 3 implementations, dynamic casting of an object inheriting from
Baseto the target classBaseis as fast as the base-line. kcl_dynamic_castperforms best in all scenarios.- The ordering of the objects in memory has a significant influence on performance. The worst case for
dynamic_castwith ordered objects performs about the same as the best case forkcl_dynamic_castwith shuffled objects. - In
priori_cast, the latency grows with the distance between the target class and the base class. However, this characteristic is less pronounced when the objects are randomly shuffled in memory, or when the class hierarchy is not deep. The latency is independent of the operand class (independent of the cast being successful or not), which makes it a constant-time operation. - In
dynamic_cast, for successful casts, the latency grows with the distance between the operand class and the base class (about 16% of base-line speed for casts to the same class when objects are aligned, and 2% when objects are shuffled). Non-successful casts have a latency independent of the target class.
If you think that I’ve made a mistake in interpreting the results, please leave a comment below.
Program output
The results were generated on an AMD Ryzen 5 3600 CPU, with the frequency fixed at 3600 MHz.
The unit of performance is given in MHz, i.e. million “units of work” per second. Percentages are given relative to the base-line. The horizontal bars illustrate the given percentages.
Run 1 (objects aligned)
Class hierarchy: deep
Cast type: Mostly successful (cast from class G)
Base-line: static_cast
-: 987.2 MHz (100%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 969.9 MHz ( 98%) [2000000] |------------------------------------------------------------...
B: 27.6 MHz ( 3%) [2000000] |------|
C: 32.9 MHz ( 3%) [2000000] |-------|
D: 40.7 MHz ( 4%) [2000000] |---------|
E: 54.1 MHz ( 5%) [2000000] |-------------|
F: 79.4 MHz ( 8%) [2000000] |-------------------|
G: 152.0 MHz ( 15%) [2000000] |------------------------------------|
H: 22.8 MHz ( 2%) [ 0] |-----|
Z: 22.1 MHz ( 2%) [ 0] |-----|
------------
AVG: 48.0 MHz |===========|
Implementation: priori_cast
A: 912.0 MHz ( 92%) [2000000] |------------------------------------------------------------...
B: 120.8 MHz ( 12%) [2000000] |-----------------------------|
C: 79.8 MHz ( 8%) [2000000] |-------------------|
D: 58.0 MHz ( 6%) [2000000] |--------------|
E: 42.6 MHz ( 4%) [2000000] |----------|
F: 35.6 MHz ( 4%) [2000000] |--------|
G: 32.4 MHz ( 3%) [2000000] |-------|
H: 9.0 MHz ( 1%) [ 0] |--|
Z: 9.0 MHz ( 1%) [ 0] |--|
------------
AVG: 43.0 MHz |==========|
Implementation: kcl_dynamic_cast
A: 963.9 MHz ( 98%) [2000000] |------------------------------------------------------------...
B: 190.0 MHz ( 19%) [2000000] |----------------------------------------------|
C: 188.4 MHz ( 19%) [2000000] |---------------------------------------------|
D: 196.3 MHz ( 20%) [2000000] |-----------------------------------------------|
E: 199.5 MHz ( 20%) [2000000] |------------------------------------------------|
F: 224.9 MHz ( 23%) [2000000] |------------------------------------------------------|
G: 220.6 MHz ( 22%) [2000000] |-----------------------------------------------------|
H: 146.7 MHz ( 15%) [ 0] |-----------------------------------|
Z: 154.1 MHz ( 16%) [ 0] |-------------------------------------|
------------
AVG: 168.9 MHz |=========================================|
Cast type: Mostly failed (cast from class B)
Base-line: static_cast
-: 989.6 MHz (100%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 973.2 MHz ( 99%) [2000000] |------------------------------------------------------------...
B: 149.9 MHz ( 15%) [2000000] |------------------------------------|
C: 70.5 MHz ( 7%) [ 0] |-----------------|
D: 69.0 MHz ( 7%) [ 0] |----------------|
E: 70.0 MHz ( 7%) [ 0] |-----------------|
F: 68.7 MHz ( 7%) [ 0] |----------------|
G: 69.5 MHz ( 7%) [ 0] |----------------|
H: 68.6 MHz ( 7%) [ 0] |----------------|
Z: 68.3 MHz ( 7%) [ 0] |----------------|
------------
AVG: 70.5 MHz |=================|
Implementation: priori_cast
A: 970.9 MHz ( 98%) [2000000] |------------------------------------------------------------...
B: 120.7 MHz ( 12%) [2000000] |-----------------------------|
C: 77.4 MHz ( 8%) [ 0] |------------------|
D: 54.7 MHz ( 6%) [ 0] |-------------|
E: 45.3 MHz ( 5%) [ 0] |-----------|
F: 37.8 MHz ( 4%) [ 0] |---------|
G: 33.0 MHz ( 3%) [ 0] |--------|
H: 9.2 MHz ( 1%) [ 0] |--|
Z: 9.1 MHz ( 1%) [ 0] |--|
------------
AVG: 43.0 MHz |==========|
Implementation: kcl_dynamic_cast
A: 974.2 MHz ( 99%) [2000000] |------------------------------------------------------------...
B: 239.5 MHz ( 24%) [2000000] |----------------------------------------------------------|
C: 192.0 MHz ( 19%) [ 0] |----------------------------------------------|
D: 190.4 MHz ( 19%) [ 0] |----------------------------------------------|
E: 194.9 MHz ( 20%) [ 0] |-----------------------------------------------|
F: 198.2 MHz ( 20%) [ 0] |------------------------------------------------|
G: 194.8 MHz ( 20%) [ 0] |-----------------------------------------------|
H: 199.0 MHz ( 20%) [ 0] |------------------------------------------------|
Z: 187.9 MHz ( 19%) [ 0] |---------------------------------------------|
------------
AVG: 177.4 MHz |===========================================|
Cast type: Mixed (cast from random classes)
Base-line: static_cast
-: 997.0 MHz (101%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 943.8 MHz ( 96%) [2000000] |------------------------------------------------------------...
B: 39.2 MHz ( 4%) [1714818] |---------|
C: 44.4 MHz ( 4%) [1428952] |----------|
D: 47.2 MHz ( 5%) [1144295] |-----------|
E: 46.0 MHz ( 5%) [ 858212] |-----------|
F: 42.9 MHz ( 4%) [ 572465] |----------|
G: 37.3 MHz ( 4%) [ 286584] |---------|
H: 31.0 MHz ( 3%) [ 0] |-------|
Z: 29.2 MHz ( 3%) [ 0] |-------|
------------
AVG: 35.3 MHz |========|
Implementation: priori_cast
A: 980.9 MHz ( 99%) [2000000] |------------------------------------------------------------...
B: 105.5 MHz ( 11%) [1714818] |-------------------------|
C: 67.7 MHz ( 7%) [1428952] |----------------|
D: 45.7 MHz ( 5%) [1144295] |-----------|
E: 37.2 MHz ( 4%) [ 858212] |---------|
F: 33.1 MHz ( 3%) [ 572465] |--------|
G: 31.1 MHz ( 3%) [ 286584] |-------|
H: 9.0 MHz ( 1%) [ 0] |--|
Z: 8.9 MHz ( 1%) [ 0] |--|
------------
AVG: 37.6 MHz |=========|
Implementation: kcl_dynamic_cast
A: 827.8 MHz ( 84%) [2000000] |------------------------------------------------------------...
B: 86.2 MHz ( 9%) [1714818] |--------------------|
C: 90.0 MHz ( 9%) [1428952] |---------------------|
D: 93.2 MHz ( 9%) [1144295] |----------------------|
E: 92.9 MHz ( 9%) [ 858212] |----------------------|
F: 86.2 MHz ( 9%) [ 572465] |--------------------|
G: 81.3 MHz ( 8%) [ 286584] |-------------------|
H: 78.4 MHz ( 8%) [ 0] |-------------------|
Z: 78.7 MHz ( 8%) [ 0] |-------------------|
------------
AVG: 76.3 MHz |==================|
Class hierarchy: shallow
Cast type: Mostly successful (cast from class G)
Base-line: static_cast
-: 864.3 MHz ( 88%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 916.6 MHz ( 93%) [2000000] |------------------------------------------------------------...
B: 69.8 MHz ( 7%) [ 0] |----------------|
C: 69.0 MHz ( 7%) [ 0] |----------------|
D: 62.6 MHz ( 6%) [ 0] |---------------|
E: 62.0 MHz ( 6%) [ 0] |---------------|
F: 69.8 MHz ( 7%) [ 0] |----------------|
G: 147.5 MHz ( 15%) [2000000] |-----------------------------------|
H: 69.9 MHz ( 7%) [ 0] |----------------|
Z: 68.9 MHz ( 7%) [ 0] |----------------|
------------
AVG: 68.8 MHz |================|
Implementation: priori_cast
A: 961.1 MHz ( 97%) [2000000] |------------------------------------------------------------...
B: 26.0 MHz ( 3%) [ 0] |------|
C: 23.6 MHz ( 2%) [ 0] |-----|
D: 20.5 MHz ( 2%) [ 0] |----|
E: 19.5 MHz ( 2%) [ 0] |----|
F: 15.6 MHz ( 2%) [ 0] |---|
G: 14.0 MHz ( 1%) [2000000] |---|
H: 8.6 MHz ( 1%) [ 0] |--|
Z: 9.5 MHz ( 1%) [ 0] |--|
------------
AVG: 15.3 MHz |===|
Implementation: kcl_dynamic_cast
A: 984.7 MHz (100%) [2000000] |------------------------------------------------------------...
B: 180.4 MHz ( 18%) [2000000] |-------------------------------------------|
C: 188.6 MHz ( 19%) [2000000] |---------------------------------------------|
D: 203.0 MHz ( 21%) [2000000] |-------------------------------------------------|
E: 210.0 MHz ( 21%) [2000000] |---------------------------------------------------|
F: 214.8 MHz ( 22%) [2000000] |----------------------------------------------------|
G: 225.9 MHz ( 23%) [2000000] |------------------------------------------------------|
H: 152.4 MHz ( 15%) [ 0] |-------------------------------------|
Z: 162.5 MHz ( 16%) [ 0] |---------------------------------------|
------------
AVG: 170.8 MHz |=========================================|
Cast type: Mostly failed (cast from class B)
Base-line: static_cast
-: 950.1 MHz ( 96%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 962.0 MHz ( 97%) [2000000] |------------------------------------------------------------...
B: 150.8 MHz ( 15%) [2000000] |------------------------------------|
C: 68.0 MHz ( 7%) [ 0] |----------------|
D: 68.8 MHz ( 7%) [ 0] |----------------|
E: 67.0 MHz ( 7%) [ 0] |----------------|
F: 68.6 MHz ( 7%) [ 0] |----------------|
G: 67.2 MHz ( 7%) [ 0] |----------------|
H: 68.8 MHz ( 7%) [ 0] |----------------|
Z: 67.0 MHz ( 7%) [ 0] |----------------|
------------
AVG: 69.6 MHz |================|
Implementation: priori_cast
A: 937.2 MHz ( 95%) [2000000] |------------------------------------------------------------...
B: 25.3 MHz ( 3%) [2000000] |------|
C: 22.3 MHz ( 2%) [ 0] |-----|
D: 20.2 MHz ( 2%) [ 0] |----|
E: 18.9 MHz ( 2%) [ 0] |----|
F: 15.6 MHz ( 2%) [ 0] |---|
G: 14.4 MHz ( 1%) [ 0] |---|
H: 8.9 MHz ( 1%) [ 0] |--|
Z: 9.9 MHz ( 1%) [ 0] |--|
------------
AVG: 15.1 MHz |===|
Implementation: kcl_dynamic_cast
A: 969.9 MHz ( 98%) [2000000] |------------------------------------------------------------...
B: 231.2 MHz ( 23%) [2000000] |--------------------------------------------------------|
C: 193.5 MHz ( 20%) [ 0] |-----------------------------------------------|
D: 192.5 MHz ( 20%) [ 0] |----------------------------------------------|
E: 186.5 MHz ( 19%) [ 0] |---------------------------------------------|
F: 183.6 MHz ( 19%) [ 0] |--------------------------------------------|
G: 184.4 MHz ( 19%) [ 0] |--------------------------------------------|
H: 184.4 MHz ( 19%) [ 0] |--------------------------------------------|
Z: 192.2 MHz ( 19%) [ 0] |----------------------------------------------|
------------
AVG: 172.1 MHz |=========================================|
Cast type: Mixed (cast from random classes)
Base-line: static_cast
-: 1004.5 MHz (102%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 966.2 MHz ( 98%) [2000000] |------------------------------------------------------------...
B: 69.4 MHz ( 7%) [ 286159] |----------------|
C: 69.1 MHz ( 7%) [ 285844] |----------------|
D: 63.3 MHz ( 6%) [ 285454] |---------------|
E: 57.7 MHz ( 6%) [ 285702] |--------------|
F: 63.2 MHz ( 6%) [ 285421] |---------------|
G: 58.1 MHz ( 6%) [ 286243] |--------------|
H: 58.0 MHz ( 6%) [ 0] |--------------|
Z: 68.2 MHz ( 7%) [ 0] |----------------|
------------
AVG: 56.3 MHz |=============|
Implementation: priori_cast
A: 940.7 MHz ( 95%) [2000000] |------------------------------------------------------------...
B: 25.7 MHz ( 3%) [ 286159] |------|
C: 23.2 MHz ( 2%) [ 285844] |-----|
D: 19.8 MHz ( 2%) [ 285454] |----|
E: 18.4 MHz ( 2%) [ 285702] |----|
F: 15.3 MHz ( 2%) [ 285421] |---|
G: 14.4 MHz ( 1%) [ 286243] |---|
H: 8.5 MHz ( 1%) [ 0] |--|
Z: 9.4 MHz ( 1%) [ 0] |--|
------------
AVG: 15.0 MHz |===|
Implementation: kcl_dynamic_cast
A: 889.3 MHz ( 90%) [2000000] |------------------------------------------------------------...
B: 94.5 MHz ( 10%) [1714823] |----------------------|
C: 96.8 MHz ( 10%) [1428664] |-----------------------|
D: 94.0 MHz ( 10%) [1142820] |----------------------|
E: 92.8 MHz ( 9%) [ 857366] |----------------------|
F: 89.0 MHz ( 9%) [ 571664] |---------------------|
G: 86.9 MHz ( 9%) [ 286243] |---------------------|
H: 82.9 MHz ( 8%) [ 0] |--------------------|
Z: 83.9 MHz ( 9%) [ 0] |--------------------|
------------
AVG: 80.1 MHz |===================|
Class hierarchy: balanced
Cast type: Mixed (cast from random classes)
Base-line: static_cast
-: 980.9 MHz ( 99%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 984.7 MHz (100%) [2000000] |------------------------------------------------------------...
B: 48.8 MHz ( 5%) [ 858197] |-----------|
C: 43.5 MHz ( 4%) [ 285844] |----------|
D: 42.4 MHz ( 4%) [ 286062] |----------|
E: 44.3 MHz ( 4%) [ 856053] |----------|
F: 46.3 MHz ( 5%) [ 285411] |-----------|
G: 47.8 MHz ( 5%) [ 285525] |-----------|
H: 39.8 MHz ( 4%) [ 0] |---------|
Z: 42.0 MHz ( 4%) [ 0] |----------|
------------
AVG: 39.4 MHz |=========|
Implementation: priori_cast
A: 982.3 MHz (100%) [2000000] |------------------------------------------------------------...
B: 11.8 MHz ( 1%) [ 858197] |--|
C: 12.3 MHz ( 1%) [ 285844] |--|
D: 10.8 MHz ( 1%) [ 286062] |--|
E: 10.2 MHz ( 1%) [ 856053] |--|
F: 9.4 MHz ( 1%) [ 285411] |--|
G: 9.9 MHz ( 1%) [ 285525] |--|
H: 8.8 MHz ( 1%) [ 0] |--|
Z: 9.7 MHz ( 1%) [ 0] |--|
------------
AVG: 9.2 MHz |==|
Implementation: kcl_dynamic_cast
A: 922.1 MHz ( 93%) [2000000] |------------------------------------------------------------...
B: 95.4 MHz ( 10%) [ 858197] |-----------------------|
C: 90.9 MHz ( 9%) [ 285844] |----------------------|
D: 90.9 MHz ( 9%) [ 286062] |----------------------|
E: 92.4 MHz ( 9%) [ 856053] |----------------------|
F: 88.0 MHz ( 9%) [ 285411] |---------------------|
G: 89.0 MHz ( 9%) [ 285525] |---------------------|
H: 88.3 MHz ( 9%) [ 0] |---------------------|
Z: 88.0 MHz ( 9%) [ 0] |---------------------|
------------
AVG: 80.3 MHz |===================|
Run 2 (objects shuffled)
Class hierarchy: deep
Cast type: Mostly successful (cast from class G)
Base-line: static_cast
-: 956.5 MHz (100%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 945.6 MHz ( 99%) [2000000] |------------------------------------------------------------...
B: 6.4 MHz ( 1%) [2000000] |-|
C: 6.7 MHz ( 1%) [2000000] |-|
D: 7.0 MHz ( 1%) [2000000] |-|
E: 7.4 MHz ( 1%) [2000000] |-|
F: 13.3 MHz ( 1%) [2000000] |---|
G: 20.3 MHz ( 2%) [2000000] |-----|
H: 6.2 MHz ( 1%) [ 0] |-|
Z: 6.1 MHz ( 1%) [ 0] |-|
------------
AVG: 8.1 MHz |==|
Implementation: priori_cast
A: 971.3 MHz (102%) [2000000] |------------------------------------------------------------...
B: 14.4 MHz ( 2%) [2000000] |---|
C: 13.8 MHz ( 1%) [2000000] |---|
D: 7.7 MHz ( 1%) [2000000] |-|
E: 7.4 MHz ( 1%) [2000000] |-|
F: 7.3 MHz ( 1%) [2000000] |-|
G: 7.1 MHz ( 1%) [2000000] |-|
H: 9.6 MHz ( 1%) [ 0] |--|
Z: 9.8 MHz ( 1%) [ 0] |--|
------------
AVG: 8.6 MHz |==|
Implementation: kcl_dynamic_cast
A: 951.5 MHz ( 99%) [2000000] |------------------------------------------------------------...
B: 27.3 MHz ( 3%) [2000000] |------|
C: 27.6 MHz ( 3%) [2000000] |------|
D: 28.0 MHz ( 3%) [2000000] |-------|
E: 28.7 MHz ( 3%) [2000000] |-------|
F: 34.2 MHz ( 4%) [2000000] |--------|
G: 35.0 MHz ( 4%) [2000000] |--------|
H: 21.1 MHz ( 2%) [ 0] |-----|
Z: 21.2 MHz ( 2%) [ 0] |-----|
------------
AVG: 24.8 MHz |======|
Cast type: Mostly failed (cast from class B)
Base-line: static_cast
-: 932.0 MHz ( 97%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 924.6 MHz ( 97%) [2000000] |------------------------------------------------------------...
B: 20.4 MHz ( 2%) [2000000] |-----|
C: 7.9 MHz ( 1%) [ 0] |-|
D: 7.9 MHz ( 1%) [ 0] |-|
E: 7.9 MHz ( 1%) [ 0] |-|
F: 7.9 MHz ( 1%) [ 0] |-|
G: 7.8 MHz ( 1%) [ 0] |-|
H: 7.9 MHz ( 1%) [ 0] |-|
Z: 7.9 MHz ( 1%) [ 0] |-|
------------
AVG: 8.4 MHz |==|
Implementation: priori_cast
A: 981.8 MHz (103%) [2000000] |------------------------------------------------------------...
B: 14.7 MHz ( 2%) [2000000] |---|
C: 14.1 MHz ( 1%) [ 0] |---|
D: 7.8 MHz ( 1%) [ 0] |-|
E: 7.6 MHz ( 1%) [ 0] |-|
F: 7.4 MHz ( 1%) [ 0] |-|
G: 7.3 MHz ( 1%) [ 0] |-|
H: 9.4 MHz ( 1%) [ 0] |--|
Z: 9.6 MHz ( 1%) [ 0] |--|
------------
AVG: 8.7 MHz |==|
Implementation: kcl_dynamic_cast
A: 966.2 MHz (101%) [2000000] |------------------------------------------------------------...
B: 34.5 MHz ( 4%) [2000000] |--------|
C: 27.9 MHz ( 3%) [ 0] |-------|
D: 27.9 MHz ( 3%) [ 0] |-------|
E: 28.0 MHz ( 3%) [ 0] |-------|
F: 28.0 MHz ( 3%) [ 0] |-------|
G: 28.0 MHz ( 3%) [ 0] |-------|
H: 27.9 MHz ( 3%) [ 0] |-------|
Z: 27.5 MHz ( 3%) [ 0] |------|
------------
AVG: 25.5 MHz |======|
Cast type: Mixed (cast from random classes)
Base-line: static_cast
-: 985.2 MHz (103%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 962.5 MHz (101%) [2000000] |------------------------------------------------------------...
B: 7.0 MHz ( 1%) [1714818] |-|
C: 7.3 MHz ( 1%) [1428952] |-|
D: 7.4 MHz ( 1%) [1144295] |-|
E: 7.4 MHz ( 1%) [ 858212] |-|
F: 7.3 MHz ( 1%) [ 572465] |-|
G: 7.0 MHz ( 1%) [ 286584] |-|
H: 6.7 MHz ( 1%) [ 0] |-|
Z: 6.5 MHz ( 1%) [ 0] |-|
------------
AVG: 6.3 MHz |=|
Implementation: priori_cast
A: 981.4 MHz (103%) [2000000] |------------------------------------------------------------...
B: 13.8 MHz ( 1%) [1714818] |---|
C: 12.7 MHz ( 1%) [1428952] |---|
D: 6.8 MHz ( 1%) [1144295] |-|
E: 6.7 MHz ( 1%) [ 858212] |-|
F: 7.0 MHz ( 1%) [ 572465] |-|
G: 7.0 MHz ( 1%) [ 286584] |-|
H: 9.1 MHz ( 1%) [ 0] |--|
Z: 10.0 MHz ( 1%) [ 0] |--|
------------
AVG: 8.1 MHz |==|
Implementation: kcl_dynamic_cast
A: 945.2 MHz ( 99%) [2000000] |------------------------------------------------------------...
B: 22.6 MHz ( 2%) [1714818] |-----|
C: 23.8 MHz ( 2%) [1428952] |-----|
D: 24.0 MHz ( 3%) [1144295] |------|
E: 23.6 MHz ( 2%) [ 858212] |-----|
F: 22.7 MHz ( 2%) [ 572465] |-----|
G: 21.4 MHz ( 2%) [ 286584] |-----|
H: 20.2 MHz ( 2%) [ 0] |-----|
Z: 20.3 MHz ( 2%) [ 0] |-----|
------------
AVG: 19.8 MHz |====|
Class hierarchy: shallow
Cast type: Mostly successful (cast from class G)
Base-line: static_cast
-: 980.4 MHz (103%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 999.5 MHz (104%) [2000000] |------------------------------------------------------------...
B: 8.0 MHz ( 1%) [ 0] |--|
C: 8.0 MHz ( 1%) [ 0] |-|
D: 7.7 MHz ( 1%) [ 0] |-|
E: 7.8 MHz ( 1%) [ 0] |-|
F: 8.0 MHz ( 1%) [ 0] |--|
G: 20.5 MHz ( 2%) [2000000] |-----|
H: 8.0 MHz ( 1%) [ 0] |--|
Z: 7.9 MHz ( 1%) [ 0] |-|
------------
AVG: 8.4 MHz |==|
Implementation: priori_cast
A: 953.3 MHz (100%) [2000000] |------------------------------------------------------------...
B: 7.2 MHz ( 1%) [ 0] |-|
C: 6.8 MHz ( 1%) [ 0] |-|
D: 6.7 MHz ( 1%) [ 0] |-|
E: 6.5 MHz ( 1%) [ 0] |-|
F: 6.0 MHz ( 1%) [ 0] |-|
G: 5.8 MHz ( 1%) [2000000] |-|
H: 9.0 MHz ( 1%) [ 0] |--|
Z: 9.8 MHz ( 1%) [ 0] |--|
------------
AVG: 6.4 MHz |=|
Implementation: kcl_dynamic_cast
A: 981.4 MHz (103%) [2000000] |------------------------------------------------------------...
B: 27.8 MHz ( 3%) [2000000] |------|
C: 27.7 MHz ( 3%) [2000000] |------|
D: 28.4 MHz ( 3%) [2000000] |-------|
E: 34.4 MHz ( 4%) [2000000] |--------|
F: 34.8 MHz ( 4%) [2000000] |--------|
G: 35.5 MHz ( 4%) [2000000] |--------|
H: 21.5 MHz ( 2%) [ 0] |-----|
Z: 21.5 MHz ( 2%) [ 0] |-----|
------------
AVG: 25.7 MHz |======|
Cast type: Mostly failed (cast from class B)
Base-line: static_cast
-: 994.5 MHz (104%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 981.4 MHz (103%) [2000000] |------------------------------------------------------------...
B: 20.2 MHz ( 2%) [2000000] |-----|
C: 7.9 MHz ( 1%) [ 0] |-|
D: 7.9 MHz ( 1%) [ 0] |-|
E: 7.7 MHz ( 1%) [ 0] |-|
F: 7.7 MHz ( 1%) [ 0] |-|
G: 7.8 MHz ( 1%) [ 0] |-|
H: 7.8 MHz ( 1%) [ 0] |-|
Z: 7.8 MHz ( 1%) [ 0] |-|
------------
AVG: 8.3 MHz |==|
Implementation: priori_cast
A: 920.8 MHz ( 96%) [2000000] |------------------------------------------------------------...
B: 6.9 MHz ( 1%) [2000000] |-|
C: 6.8 MHz ( 1%) [ 0] |-|
D: 6.7 MHz ( 1%) [ 0] |-|
E: 6.5 MHz ( 1%) [ 0] |-|
F: 6.1 MHz ( 1%) [ 0] |-|
G: 5.8 MHz ( 1%) [ 0] |-|
H: 8.5 MHz ( 1%) [ 0] |--|
Z: 10.2 MHz ( 1%) [ 0] |--|
------------
AVG: 6.4 MHz |=|
Implementation: kcl_dynamic_cast
A: 984.3 MHz (103%) [2000000] |------------------------------------------------------------...
B: 35.0 MHz ( 4%) [2000000] |--------|
C: 28.3 MHz ( 3%) [ 0] |-------|
D: 28.3 MHz ( 3%) [ 0] |-------|
E: 28.2 MHz ( 3%) [ 0] |-------|
F: 28.2 MHz ( 3%) [ 0] |-------|
G: 28.1 MHz ( 3%) [ 0] |-------|
H: 28.3 MHz ( 3%) [ 0] |-------|
Z: 28.3 MHz ( 3%) [ 0] |-------|
------------
AVG: 25.9 MHz |======|
Cast type: Mixed (cast from random classes)
Base-line: static_cast
-: 996.5 MHz (104%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 1003.5 MHz (105%) [2000000] |------------------------------------------------------------...
B: 7.8 MHz ( 1%) [ 286159] |-|
C: 7.8 MHz ( 1%) [ 285844] |-|
D: 7.8 MHz ( 1%) [ 285454] |-|
E: 7.7 MHz ( 1%) [ 285702] |-|
F: 7.8 MHz ( 1%) [ 285421] |-|
G: 7.8 MHz ( 1%) [ 286243] |-|
H: 7.7 MHz ( 1%) [ 0] |-|
Z: 8.0 MHz ( 1%) [ 0] |--|
------------
AVG: 6.9 MHz |=|
Implementation: priori_cast
A: 966.2 MHz (101%) [2000000] |------------------------------------------------------------...
B: 7.0 MHz ( 1%) [ 286159] |-|
C: 6.7 MHz ( 1%) [ 285844] |-|
D: 6.5 MHz ( 1%) [ 285454] |-|
E: 6.4 MHz ( 1%) [ 285702] |-|
F: 5.9 MHz ( 1%) [ 285421] |-|
G: 5.7 MHz ( 1%) [ 286243] |-|
H: 8.6 MHz ( 1%) [ 0] |--|
Z: 9.7 MHz ( 1%) [ 0] |--|
------------
AVG: 6.3 MHz |=|
Implementation: kcl_dynamic_cast
A: 769.8 MHz ( 80%) [2000000] |------------------------------------------------------------...
B: 22.7 MHz ( 2%) [1714823] |-----|
C: 24.2 MHz ( 3%) [1428664] |------|
D: 24.3 MHz ( 3%) [1142820] |------|
E: 23.9 MHz ( 3%) [ 857366] |------|
F: 23.0 MHz ( 2%) [ 571664] |-----|
G: 22.0 MHz ( 2%) [ 286243] |-----|
H: 20.4 MHz ( 2%) [ 0] |-----|
Z: 20.5 MHz ( 2%) [ 0] |-----|
------------
AVG: 20.1 MHz |=====|
Class hierarchy: balanced
Cast type: Mixed (cast from random classes)
Base-line: static_cast
-: 985.7 MHz (103%) [2000000] |------------------------------------------------------------...
Implementation: dynamic_cast
A: 988.1 MHz (103%) [2000000] |------------------------------------------------------------...
B: 11.4 MHz ( 1%) [ 858197] |--|
C: 7.4 MHz ( 1%) [ 285844] |-|
D: 7.3 MHz ( 1%) [ 286062] |-|
E: 9.4 MHz ( 1%) [ 856053] |--|
F: 7.3 MHz ( 1%) [ 285411] |-|
G: 7.4 MHz ( 1%) [ 285525] |-|
H: 6.9 MHz ( 1%) [ 0] |-|
Z: 7.1 MHz ( 1%) [ 0] |-|
------------
AVG: 7.1 MHz |=|
Implementation: priori_cast
A: 978.5 MHz (102%) [2000000] |------------------------------------------------------------...
B: 5.1 MHz ( 1%) [ 858197] |-|
C: 5.4 MHz ( 1%) [ 285844] |-|
D: 5.1 MHz ( 1%) [ 286062] |-|
E: 4.8 MHz ( 0%) [ 856053] |-|
F: 4.7 MHz ( 0%) [ 285411] |-|
G: 5.0 MHz ( 1%) [ 285525] |-|
H: 8.8 MHz ( 1%) [ 0] |--|
Z: 9.7 MHz ( 1%) [ 0] |--|
------------
AVG: 5.4 MHz |=|
Implementation: kcl_dynamic_cast
A: 934.1 MHz ( 98%) [2000000] |------------------------------------------------------------...
B: 24.4 MHz ( 3%) [ 858197] |------|
C: 23.0 MHz ( 2%) [ 285844] |-----|
D: 23.1 MHz ( 2%) [ 286062] |-----|
E: 24.1 MHz ( 3%) [ 856053] |------|
F: 22.0 MHz ( 2%) [ 285411] |-----|
G: 23.1 MHz ( 2%) [ 285525] |-----|
H: 22.2 MHz ( 2%) [ 0] |-----|
Z: 22.3 MHz ( 2%) [ 0] |-----|
------------
AVG: 20.5 MHz |=====|
If you found a mistake in this blog post, or would like to suggest an improvement to this blog post,
please me an e-mail to michael@franzl.name; as subject
please use the prefix "Comment to blog post" and append the post title.