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Is the “struct hack” technically undefined behavior?
...des in the list of undefined behavior:
An array subscript is out of range, even if an object is apparently accessible with the given subscript (as in the lvalue expression a[1][7] given the declaration int a[4][5]) (6.5.6).
Paragraph 8 of Section 6.5.6 Additive operators has another ment...
Iteration over std::vector: unsigned vs signed index variable
...on't know. That will ensure your code runs as generic as possible.
Using Range C++11
for(auto const& value: a) {
/* std::cout << value; ... */
Using indices
for(std::vector<int>::size_type i = 0; i != v.size(); i++) {
/* std::cout << v[i]; ... */
}
Using arra...
内存优化总结:ptmalloc、tcmalloc和jemalloc - 操作系统(内核) - 清泛网 - ...
...16个table，每个5M row。
OLTP_RO测试包含5个select查询：select_ranges, select_order_ranges, select_distinct_ranges, select_sum_ranges,
可以看到在多核心或者多线程的场景下， jemalloc和tcmalloc带来的tps增加非常明显。
参考资料
glibc内存管理ptmalloc...
Using TortoiseSVN how do I merge changes from the trunk to a branch and vice versa?
...two enable subversion 1.5's merge tracking.
TortoiseSVN's options merge a range or revisions maps to method 3 when your repository is 1.5+ or to method one when your repository is older.
When merging features over to a release/maintenance branch you should use the 'Merge a range of revisions' comm...
Get the last non-empty cell in a column in Google Sheets
...
Question. If instead of A:A, there is an importrange(), how can this be rewritten without doing the same importrange() 4 times?
– Ruby
Mar 6 '19 at 21:54
...
Switch statement for greater-than/less-than
...switch-immediate 2.0 1.1 2.0 1.0 2.8 1.3
switch-range 38.1 10.6 2.6 7.3 20.9 10.4
switch-range2 31.9 8.3 2.0 4.5 9.5 6.9
switch-indirect-array 35.2 9.6 4.2 5.5 10.7 8.6
array-linear-switch 3.6 ...
Performance of Arrays vs. Lists
...Array need to use:
So often as possible. It's fast and takes smallest RAM range for same amount information.
If you know exact count of cells needed
If data saved in array < 85000 b (85000/32 = 2656 elements for integer data)
If needed high Random Access speed
List need to use:
If needed to a...
Python Regex - How to Get Positions and Values of Matches
...Z])"
for match in re.finditer(regex_with_3_groups, string):
for idx in range(0, 4):
print(match.span(idx), match.group(idx))
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UnicodeDecodeError: 'ascii' codec can't decode byte 0xd1 in position 2: ordinal not in range(128)
...'ascii' codec can't encode character u'\xf1' in position 2: ordinal not in range(128)
– Vikash Mishra
Nov 21 '16 at 13:45
...
Make elasticsearch only return certain fields?
...ws_on_things"
}
},
"filter":{
"range":{
"doc.timestamp_utc":{
"gte":1451606400000,
"lt":1483228800000,
"format":"epoch_millis"
}
}
}
}
},
...