Re: [Gnuplot-info] Plot matrix with GNUplot. Slow

[Ethan A M. <eam...@gm...>]

On Thursday, 16 May 2013, FortCpp wrote:
> I am using GNUplot for plotting a small matrix. The matrix is 100x100 by
> size. e.g.
> 
> 1.23212 2.43123 -1.24312 ......
> -4.23123 2.00458 5.60234 ......
> ......
> The data is not neatly stored in the file. So from C++ point of view, due to
> the lack of length per data, there is no way to load a whole number, but it
> has to check when the number is loading. I guess this should be the reason
> of the slow plotting speed.
> 
> Now I have 3 questions:
> Q1: Is loading the bottle neck?
> 
> Q2: If I can make the data file neatly stored (setw). e.g.
> 
>  1.23212  2.43123 -1.24312 ......
> -4.23123  2.00458  5.60234 ......
> ......
> Does the plotting speed get any improvement? (Maybe GNUplot can check what
> the pattern is. Thus improve the loading speed. Not sure.)

No. That won't make any difference.

> 
> Q3: Any other options that I can set to make it faster?

gnuplot> help fpe

 The `set datafile nofpe_trap` command tells gnuplot not to re-initialize a
 floating point exception handler before every expression evaluation used while
 reading data from an input file.  This can significantly speed data input from
 very large files at the risk of program termination if a floating-point
 exception is generated.

You haven't shown us the commands you use to read the file,
so I don't know if this is relevant to your case.

There is a recent patch in the CVS version that hugely speeds up
reading binary matrices, but since the matrix you show is in 
ascii that wouldn't help.

	Ethan


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