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one more simple folly::join optimization

Summary:
Before:

_bin/folly/test/string_test --benchmark --bm_regex=join --bm_min_usec=1000000
============================================================================
folly/test/StringTest.cpp                       relative  time/iter  iters/s
============================================================================
joinCharStr                                                  3.59us  278.29K
joinStrStr                                                   4.44us  225.09K
joinInt                                                     10.55us   94.76K
============================================================================

And after:

_bin/folly/test/string_test --benchmark --bm_regex=join --bm_min_usec=1000000
============================================================================
folly/test/StringTest.cpp                       relative  time/iter  iters/s
============================================================================
joinCharStr                                                  3.61us  277.01K
joinStrStr                                                   3.77us  264.97K
joinInt                                                      9.92us  100.81K
============================================================================

Test Plan: unittests, benchmark

Reviewed By: tudorb@fb.com

FB internal diff: D552364
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1 parent ff25e3b commit 5df0c9714e235fc704cfd03aea833fe8163d0058 @philippv philippv committed with tudor Aug 17, 2012
Showing with 15 additions and 1 deletion.
  1. +5 −0 folly/String-inl.h
  2. +10 −1 folly/test/StringTest.cpp
View
@@ -312,6 +312,11 @@ void internalJoinAppend(Delim delimiter,
Iterator end,
String& output) {
assert(begin != end);
+ if (std::is_same<Delim, StringPiece>::value &&
+ delimSize(delimiter) == 1) {
+ internalJoinAppend(delimFront(delimiter), begin, end, output);
+ return;
+ }
toAppend(*begin, &output);
while (++begin != end) {
toAppend(delimiter, *begin, &output);
View
@@ -761,7 +761,16 @@ BENCHMARK(boost_splitOnSingleChar, iters) {
}
}
-BENCHMARK(joinStr, iters) {
+BENCHMARK(joinCharStr, iters) {
+ static const std::vector<std::string> input = {
+ "one", "two", "three", "four", "five", "six", "seven" };
+ for (int i = 0; i < iters << 4; ++i) {
+ std::string output;
+ folly::join(':', input, output);
+ }
+}
+
+BENCHMARK(joinStrStr, iters) {
static const std::vector<std::string> input = {
"one", "two", "three", "four", "five", "six", "seven" };
for (int i = 0; i < iters << 4; ++i) {

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