[Octave-bug-tracker] [bug #63646] Long creation times for sparseimages.m in manual due to -svgconvert option to print

[Arun Giridhar]

Update of bug #63646 (project octave):

                  Status:               Confirmed => Patch Submitted        

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Follow-up Comment #10:

I'm attaching a patch "svg.patch" that improves the performance some 25x
overall. Also two intermediate patches "time_old.patch" and "time_new.patch"
with time measurement code for reproducibility.

Baseline, unpatched 3678187f4355:


octave:1> clear all; tic; n = 200; a = 10*speye(n) + sparse(1:n,
ceil([1:n]/2),1,n,n) + sparse(ceil([1:n]/2),1:n,1,n,n); r1 = chol(a); spy(r1);
axis ij; toc, tic; print -nosvgconvert -depsc2 blah.eps; toc, tic; print
-svgconvert -depsc2 blah2.eps; toc
Elapsed time is 0.173405 seconds.
Elapsed time is 0.33665 seconds.
Elapsed time is 24.8665 seconds.


With instrumentation for time measurement but no change in functionality:


octave:1> clear all; tic; n = 200; a = 10*speye(n) + sparse(1:n,
ceil([1:n]/2),1,n,n) + sparse(ceil([1:n]/2),1:n,1,n,n); r1 = chol(a); spy(r1);
axis ij; toc, tic; print -nosvgconvert -depsc2 blah.eps; toc, tic; print
-svgconvert -depsc2 blah2.eps; toc
Elapsed time is 0.164773 seconds.
Elapsed time is 0.35028 seconds.
setup time                      0μs
merge time                      0μs
crack time                      0μs
final time                      3μs

setup time                      0μs
merge time                      0μs
crack time                      0μs
final time                      0μs

setup time                      0μs
merge time                      0μs
crack time                      0μs
final time                      0μs

setup time                     30μs
merge time               22873717μs
crack time                    787μs
final time                    388μs

Elapsed time is 23.851 seconds.


Observation: unused[0] always stays false, because jj can never be 0 in
unused[jj] = true, since jj >= ii+1.

The outer for-loop on ii can therefore be eliminated, setting it to zero.

With instrumentation and that patch:


octave:1> clear all; tic; n = 200; a = 10*speye(n) + sparse(1:n,
ceil([1:n]/2),1,n,n) + sparse(ceil([1:n]/2),1:n,1,n,n); r1 = chol(a); spy(r1);
axis ij; toc, tic; print -nosvgconvert -depsc2 blah.eps; toc, tic; print
-svgconvert -depsc2 blah2.eps; toc
Elapsed time is 0.145507 seconds.
Elapsed time is 0.336081 seconds.
setup time                      0μs
merge time                      0μs
crack time                      0μs
final time                      0μs

setup time                      0μs
merge time                      0μs
crack time                      0μs
final time                      0μs

setup time                      0μs
merge time                      0μs
crack time                      0μs
final time                      0μs

setup time                     34μs
merge time                   4861μs
crack time                    684μs
final time                    363μs

Elapsed time is 0.935894 seconds.


That nested loop becomes 22873717 / 4861 == some 4700 times faster in this
case. There may be pathological cases but hopefully those are rare.

Removing the time measurement code to give the patched performance:


octave:1> clear all; tic; n = 200; a = 10*speye(n) + sparse(1:n,
ceil([1:n]/2),1,n,n) + sparse(ceil([1:n]/2),1:n,1,n,n); r1 = chol(a); spy(r1);
axis ij; toc, tic; print -nosvgconvert -depsc2 blah.eps; toc, tic; print
-svgconvert -depsc2 blah2.eps; toc
Elapsed time is 0.171607 seconds.
Elapsed time is 0.33852 seconds.
Elapsed time is 0.931587 seconds.


It would still be nice to make the svgconvert speed the same as nosvgconvert
speed but this removes one bottleneck at least.

(file #54229, file #54230, file #54231)

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Additional Item Attachment:

File name: svg.patch                      Size:1 KB
    <https://file.savannah.gnu.org/file/svg.patch?file_id=54229>

File name: time_old.patch                 Size:2 KB
    <https://file.savannah.gnu.org/file/time_old.patch?file_id=54230>

File name: time_new.patch                 Size:3 KB
    <https://file.savannah.gnu.org/file/time_new.patch?file_id=54231>



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