Re: Faster std::map?

=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <>
Tue, 21 Aug 2007 10:21:48 GMT
On 2007-08-21 11:07, wrote:


I'm reading a sequence of 123000 records from a database which needs
to be indexed into a std::map for further processing.
Currently I've found that this process can take up to 30 seconds to
perform on a modern system with 3400 MHz cpu and 1 gb ram. I would
like to cut this time down.

I've verified the actual data reading part to take less then 10
seconds which means that the map is taking about 2/3 of the time.

while (R.Read())
R.GetInt(1)] = R.GetInt(2);
R.GetInt(1)] = R.GetInt(4);
R.GetInt(1)] = R.GetInt(3);

You can probably get a small speed-up by caching the result of
'MonthlyStat.m_UsageMap[R.GetString(0)]', so something like

while (R.Read())
   std::map<time_t, int> m& = MonthlyStat.m_UsageMap[R.GetString(0)];
   m[(time_t) R.GetInt(1)] = R.GetInt(2);
   m[(time_t) R.GetInt(1)] = R.GetInt(3);
   m[(time_t) R.GetInt(1)] = R.GetInt(4);

Erik Wikstr?m

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