Dafydd Hughes wrote:
I never figured out exactly why the climb was happening, but I found
that it happened when I turned off dsp in the abstraction, but left
the non-dsp elements running, ie continually trying to pass messages
to line~ and vd~ objects etc. Switching off the mechanics when
switching off dsp solved it for me.
Yes, sending many messages to a vline~ in a switch~'d off subpatch
causes CPU usage to rise dramatically. I nearly froze my box with Pd in
RT mode when I set the metro period to 1ms and switch~'d the subpatch
off, with the subpatch switch~'d on the cpu usage remains stable. See
attached test patch...
Why this is happening:
Sending a message to vline~ creates a t_vseg, which are stored in a
sorted linear linked list, which means the time taken to add each new
line segment would be O(n), where n is the number of existing line segments.
If the subpatch containing vline~ is switch~'d off, the t_vseg's aren't
removed by the dsp perform routine, which means that CPU usage rises
quadratically if messages are sent to the vline~ at a constant rate (I
think, it's been a while since I analyzed algorithmic time complexity).
A solution:
Use a better data structure than a linked list; a balanced tree would
reduce time complexity to O(log n) instead of O(n) (if I remember
correctly), admittedly at the cost of harder implementation.
Workaround:
Don't send messages to a switch~'d off vline~.
Claude
--
http://claudiusmaximus.goto10.org
#N canvas 0 0 450 300 10;
#N canvas 0 0 450 300 \$0-subpatch 0;
#X obj 28 17 inlet;
#X obj 26 270 outlet~;
#X obj 208 269 switch~;
#X obj 208 19 inlet;
#X obj 29 48 t b b;
#X obj 59 74 random 100;
#X obj 24 94 random 100;
#X obj 23 121 pack f f;
#X obj 24 164 vline~;
#X connect 0 0 4 0;
#X connect 3 0 2 0;
#X connect 4 0 6 0;
#X connect 4 1 5 0;
#X connect 5 0 7 1;
#X connect 6 0 7 0;
#X connect 7 0 8 0;
#X connect 8 0 1 0;
#X restore 68 117 pd \$0-subpatch;
#X obj 161 67 tgl 15 0 empty empty empty 17 7 0 10 -262144 -1 -1 0
1;
#X obj 68 68 tgl 15 0 empty empty empty 17 7 0 10 -262144 -1 -1 0 1
;
#X obj 197 67 tgl 15 0 empty empty empty 17 7 0 10 -262144 -1 -1 0
1;
#X msg 197 90 \; pd dsp \$1;
#X obj 302 88 metro 1000;
#X obj 302 111 t b b;
#X obj 302 133 cputime;
#X obj 302 64 tgl 15 0 empty empty empty 17 7 0 10 -262144 -1 -1 0
1;
#X floatatom 302 165 5 0 0 0 - - -;
#X floatatom 119 67 5 0 0 0 - - -;
#X obj 68 91 metro 10;
#X text 14 205 cputime climbs when many messages are sent to a vline~
in a switched off subpatch...;
#X connect 1 0 0 1;
#X connect 2 0 11 0;
#X connect 3 0 4 0;
#X connect 5 0 6 0;
#X connect 6 0 7 0;
#X connect 6 1 7 1;
#X connect 7 0 9 0;
#X connect 8 0 5 0;
#X connect 10 0 11 1;
#X connect 11 0 0 0;
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