re PR libstdc++/16401 (ostringstream in gcc 3.4.x very slow for big data)

2004-07-07  Paolo Carlini  <pcarlini@suse.de>

	PR libstdc++/16401
	* include/bits/sstream.tcc (overflow): When reallocating _M_string
	use an exponential grow policy.
	* testsuite/27_io/basic_stringbuf/overflow/char/1.cc: New.
	* testsuite/performance/27_io/stringbuf_overflow.cc: New.

From-SVN: r84235

libstdc++-v3/ChangeLog

@@ -1,3 +1,11 @@
+2004-07-07  Paolo Carlini  <pcarlini@suse.de>
+
+	PR libstdc++/16401
+	* include/bits/sstream.tcc (overflow): When reallocating _M_string
+	use an exponential grow policy.
+	* testsuite/27_io/basic_stringbuf/overflow/char/1.cc: New.
+	* testsuite/performance/27_io/stringbuf_overflow.cc: New.
+
 2004-07-06  Anssi Hannula  <anssi.hannula@mbnet.fi>
 
 	PR libstdc++/15928

libstdc++-v3/include/bits/sstream.tcc

@@ -83,23 +83,25 @@ namespace std
       if (__builtin_expect(__testeof, false))
 	return traits_type::not_eof(__c);
 
-      // NB: Start ostringstream buffers at 512 chars. This is an
-      // experimental value (pronounced "arbitrary" in some of the
-      // hipper english-speaking countries), and can be changed to
-      // suit particular needs.
-      const __size_type __len = std::max(__size_type(_M_string.capacity() + 1),
-					 __size_type(512));
+      const __size_type __capacity = _M_string.capacity();
+      const __size_type __max_size = _M_string.max_size();
       const bool __testput = this->pptr() < this->epptr();
-      if (__builtin_expect(!__testput && __len > _M_string.max_size(), false))
+      if (__builtin_expect(!__testput && __capacity == __max_size, false))
 	return traits_type::eof();
 
       // Try to append __c into output sequence in one of two ways.
       // Order these tests done in is unspecified by the standard.
       if (!__testput)
 	{
-	  // In virtue of DR 169 (TC) we are allowed to grow more than
-	  // one char. That's easy to implement thanks to the exponential
-	  // growth policy builtin into basic_string.
+	  // NB: Start ostringstream buffers at 512 chars. This is an
+	  // experimental value (pronounced "arbitrary" in some of the
+	  // hipper english-speaking countries), and can be changed to
+	  // suit particular needs.
+	  // Then, in virtue of DR 169 (TC) we are allowed to grow more
+	  // than one char.
+	  const __size_type __opt_len = std::max(__size_type(2 * __capacity),
+						 __size_type(512));
+	  const __size_type __len = std::min(__opt_len, __max_size);
 	  __string_type __tmp;
 	  __tmp.reserve(__len);
 	  __tmp.assign(_M_string.data(), this->epptr() - this->pbase());

libstdc++-v3/testsuite/27_io/basic_stringbuf/overflow/char/1.cc

@@ -0,0 +1,57 @@
+// 2004-07-07  Paolo Carlini  <pcarlini@suse.de>
+
+// Copyright (C) 2004 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 2, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING.  If not, write to the Free
+// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+// USA.
+
+// 27.7.1.3 basic_stringbuf overridden virtual functions.
+
+#include <sstream>
+#include <cstdlib>
+#include <testsuite_hooks.h>
+
+using namespace std;
+
+string
+data(unsigned len)
+{
+  string ret;
+  for (unsigned i = 0; i < len; ++i)
+    ret.push_back('a' + rand() % 26);
+  return ret;
+}
+
+void
+test01(unsigned iter)
+{
+  bool test __attribute__((unused)) = true;
+
+  for (unsigned n = 1; n <= iter; n *= 10)
+    {
+      const string str = data(n);
+      stringbuf sstr;
+      for (unsigned i = 0; i < n; ++i)
+	sstr.sputc(str[i]);
+      VERIFY( str == sstr.str() );
+    }
+}
+
+int main()
+{
+  test01(10000000);
+  return 0;
+}

libstdc++-v3/testsuite/performance/27_io/stringbuf_overflow.cc

@@ -0,0 +1,60 @@
+// Copyright (C) 2004 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 2, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING.  If not, write to the Free
+// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+// USA.
+
+// As a special exception, you may use this file as part of a free software
+// library without restriction.  Specifically, if other files instantiate
+// templates or use macros or inline functions from this file, or you compile
+// this file and link it with other files to produce an executable, this
+// file does not by itself cause the resulting executable to be covered by
+// the GNU General Public License.  This exception does not however
+// invalidate any other reasons why the executable file might be covered by
+// the GNU General Public License.
+
+#include <sstream>
+#include <testsuite_performance.h>
+
+// libstdc++/16401 ostringstream in gcc 3.4.x very slow for big data
+void test01()
+{
+  using namespace std;
+  using namespace __gnu_test;
+
+  time_counter time;
+  resource_counter resource;
+
+  for(unsigned n = 10000; n <= 10000000; n *= 10)
+    {
+      ostringstream oss;
+      oss << "size = " << n; 
+
+      ostringstream str;
+      start_counters(time, resource);  
+      for(unsigned i = 0; i < n; ++i)
+	str << 'a';
+      stop_counters(time, resource);
+
+      report_performance(__FILE__, oss.str(), time, resource);
+      clear_counters(time, resource);
+    }
+}
+
+int main()
+{
+  test01();
+  return 0;
+}