<html> <head> <style></style> </head> <body class='hmmessage'> Thank you very much for your email. I'll try to adjust my code, and accept your suggestions. "The question is: do all the lines you draw with cairo pass > through the bounding box?" YES. Every line I draw has to be visible. The preprocessing goes through the input coordinates, determines min/max and prepares appropriate bounding box. Having said that, is applying your suggestions going to be reasonable in terms of the speedup? I really appreciate your help. > Date: Tue, 31 Aug 2010 16:21:20 +0200 > Subject: Re: [cairo] Very large number of lines > From: ranma42@gmail.com > To: opustenom@hotmail.com > CC: cairo@cairographics.org > > On Tue, Aug 31, 2010 at 2:51 PM, necko necko <opustenom@hotmail.com> wrote: > > Thanks for the email. > > You were right about stroke the same line over itself. Therefore, I made a simple > > random coordinate generator that should more closely describe the problem > > I'm working on. > > Note that all the lines need to be shown in the pdf file (therefore I use translate > > which depends on min/max coordinate). The number of lines is from > > 20million-350million. This is the main reason I'm striving for speed (in > > processing and in displaying). > > Therefore, displaying a PNG file would be appropriate. Please consider the > > code below. > > The first translate option cairo_translate (cr, -229770, 26573); leads to > > execution time > > of around 7min, while the second one cairo_translate (cr, -429000, 35000); > > leads to > > execution time of around 1min. Is it because the invisible parts are not > > processed? > > Invisible parts are faster than visible ones because they don't have to > be composited, but they require some processing (to determine visibility). > If your random data actually resembles your true data, consider a > simple clipping function. > In my attachment I get a big speedup when declaring NO_CLIP 0. > (It does just "trivial" clipping, lines completely above/under/right/left of the > visible region are not drawn, but there are some more lines that don't > pass through it > yet are not clipped with this check) > > > > > For my application, everything within the bounding box (determined by the > > min/max coordinate) should be displayed. > > That is obvious. The question is: do all the lines you draw with cairo pass > through the bounding box? > > > I noted that the output is different when stroke() every 1000th or 100000th > > line. > > I thought this was because of the random number generator, but I tested it > > several times. > > Don't use a variable seed. Stroking will be different because of compositing, > but the differences in your attachments cannot be explained this way. > Check again your output, making sure that you do not change anything else. > (Doing the same in my attachment I cannot reproduce your problem) > > I tried to do minimum changes to your original file, but I couldn't > resist changing > the output. > Please play around a little with the defines in the file. You will see that: > - disabling clipping times get much slower > - rendering to pdf is not as crazy as before, since only a few thousands lines > are actually in the bbox (about the 0.5%) > - higher ITER_NOs are possible in reasonable amounts of time (image should > scale linearly, pdf worsen when you start swapping) > > Andrea </body> </html>