If available, use a C++17 std::pmr::unordered_set with a monotonic
buffer resource and a 256-byte stack buffer to avoid the per-element
allocations of QSet.
Results on my machine:
RESULT : tst_QStringList::removeDuplicates():"empty":
- 0.00014 msecs per iteration (total: 74, iterations: 524288)
+ 0.000031 msecs per iteration (total: 66, iterations: 2097152)
RESULT : tst_QStringList::removeDuplicates():"short-dup-0.00":
- 0.00043 msecs per iteration (total: 57, iterations: 131072)
+ 0.00013 msecs per iteration (total: 69, iterations: 524288)
RESULT : tst_QStringList::removeDuplicates():"short-dup-0.50":
- 0.00049 msecs per iteration (total: 65, iterations: 131072)
+ 0.00032 msecs per iteration (total: 85, iterations: 262144)
RESULT : tst_QStringList::removeDuplicates():"short-dup-0.66":
- 0.00057 msecs per iteration (total: 75, iterations: 131072)
+ 0.00039 msecs per iteration (total: 52, iterations: 131072)
RESULT : tst_QStringList::removeDuplicates():"short-dup-0.75":
- 0.00064 msecs per iteration (total: 85, iterations: 131072)
+ 0.00048 msecs per iteration (total: 63, iterations: 131072)
RESULT : tst_QStringList::removeDuplicates():"long-dup-0.00":
- 0.083 msecs per iteration (total: 85, iterations: 1024)
+ 0.039 msecs per iteration (total: 80, iterations: 2048)
RESULT : tst_QStringList::removeDuplicates():"long-dup-0.50":
- 0.11 msecs per iteration (total: 58, iterations: 512)
+ 0.078 msecs per iteration (total: 80, iterations: 1024)
RESULT : tst_QStringList::removeDuplicates():"long-dup-0.66":
- 0.13 msecs per iteration (total: 70, iterations: 512)
+ 0.10 msecs per iteration (total: 53, iterations: 512)
RESULT : tst_QStringList::removeDuplicates():"long-dup-0.75":
- 0.16 msecs per iteration (total: 86, iterations: 512)
+ 0.13 msecs per iteration (total: 69, iterations: 512)
When interpreting the data, take into account that each iteration
contains _also_ a deep copy of the QStringList d/t the detach from
'input'.
The pattern is used elsewhere in Qt, so I've put the class that
implements the seen set into a private header file and used in some
other places I found.
Change-Id: I1f71a82008a16d5a3818f91f290ade21d837805e
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
This commit re-applies commit f8efe8e0c9,
which was lost in the recent tools → text changes.
Change-Id: I03ce35fcb89840e5607776d67578fb75b66f6eb2
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
