From: Hugh Sasse <hgs@...>
Date: 2005-09-10T03:11:20+09:00
Subject: Re: Optimizing a single slow method

On Sat, 10 Sep 2005, Eric Hodel wrote:

> On 08 Sep 2005, at 20:46, Glenn M. Lewis wrote:
>
>> Hi!
         [...]
>>    Any ideas on how I can rewrite 'Contract.parseFile()' for
>> speed?
>>
>>    Thanks!
>> -- Glenn Lewis
>>
>>  def Contract.parseFile(file)
>>    return unless File.exists?(file)
>>    return if @@files.has_key?(file)

I'd swap those two: test of a hash will be faster than test of a
filesystem, so may as well bail out quickly. Do repeat keys happen
often?

>>    @@files[file] = 1

Maybe it only needs to be a Set, not a Hash?  Not sure how speeds
compare.

>>    print "Parsing file #{file}..."
>>    File.open(file, "rb").each_line {|line|

I think:
>>      line.chomp!
>>      # puts line
>>      fields = line.split(/,/)

might be faster as
         fields = line.chomp.split(/,/)

or if you only chomp the last field afterwards (shorter string to
change)?

>>      next if fields.size < 8

Maybe line.count(",") first, and bail out quickly? Again, how often
does this happen?

>>      datestring = fields[1]
>>      year  = datestring[0..1].to_i
>>      month = datestring[2..3].to_i
>>      day   = datestring[4..5].to_i

reduce array refs:

         year, month, day = datestring[0..5].scan(/../).collect do |s|
           s.to_i
         end

possibly


That's all I can think of just now.
         Hugh