[Octave-bug-tracker] [bug #51871] loading '-ascii' format files is slow

[count]

Follow-up Comment #5, bug #51871 (project octave):

Yeah, some details are omitted, because I think operations on the matrix is
negligible in this case.

Various improvements can be made:

Using the same benchmark as #0


tic; b = load('dat.txt'); toc


Original time (seconds)
3.30725

1) (Function get_mat_data_input_line) retval = ""; change to
retval.erase ();
Run time: 3.25221

2) Reuse tmp_stream in function read_mat_ascii_data (and (1)).
Run time: 2.90416

3) Use std::getline in get_mat_data_input_line (and (1)(2))
Run time: 1.75087

4) Use strtod to do the convertion (and (1)(2)(3)).
Run time: 1.56847

See the patch.

Note that:

  3*) By using std::getline, I drop the support of '\r' line ending (Mac OS
Classic).

  4*) By use strtod, I break the rule that stop reading at the position where
it is not part of a number. This make Octave function such as sscanf() behave
abnormally. This could be fixed by seekg() the stream, but octave_istrstream
may not support this operation well.

(file #41695)
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Additional Item Attachment:

File name: speed-up-load-ascii-v1.patch   Size:6 KB


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