Control Points

Control Points were introduced in GURPS Martial Arts: Technical Grappling. Their most significant function is that they are ST-based and reduce ST of grappled opponents.
Secondarily, the -4 to DX grappling used to do was replaced with a tiered loss based either directly on CP (basic rules) or on the % of ST subtracted (advanced rules)
Tertiarily, their payment is now required to inflict damage that used to be inflicted for free without compromising a grapple, such as Choke or Strangle or Grab and Smash. No options appear to exist to retain maximum CP after doing these attacks, even though in theory squeezing should not necessarily require a loss of control.
==Precedents==
The idea of DX penalties being accompanied by ST penalties (absent in Basic Set, where grappling only compromised DX) was found in a couple place in GURPS Martial Arts:
*MA119 "If you wound him, his shock penalty (-1 to -4) lowers his ST as well as his DX if you try to break free."
*MA124 left col "You can avoid this by hitting with less force: take a damage penalty equal to the shock penalty"
*MA124 right col "When using the “off” hand, you have the usual -4 to skill (and therefore -2 to Parry) and -2 to ST (giving -1 to punching damage)."
MA79 conversely has an inverted relationship: Using Your Legs for grappling has a DX penalty but a ST bonus. That's because it's describing inherently properties not the affects of compromise (shock/grapple)
*All-Out Attack has a similar dichotomy: choosing between +4 DX or +4 ST, or in the new technique design rules where you can take a technique penalty to do more damage or get a technique bonus to do less damage.
==Followups==
A similar approach is also taken with the The Last Gasp where FP loss which formerly only lowered ST now also lowers DX too.
*it goes even further, also lowering IQ (similar to shock) and even HT (a first!)
==Balance==
This makes it a lot harder to do these grappling attacks, so one option might be to reduce that as a guaranteed loss.
One is on pg 13:
:Active control and the shock from pain or injury both count as reducing Grip CP, though shock is momentary.
Doing that instead might work better, where focusing on strangling makes you temporarily less able to control someone than focusing on control alone, but still doesn't actually inevitably result in the loss of a grapple from squeezing very hard, which really doesn't make much sense.
Another way might be to mitigate the loss of CP lost ("damaged") by spending to attack. For example to buy Control Resistance (that normally might reduce "damage" done by an enemy doing Break Free on your grapple) and count that as "free damage" that doesn't lose CP.
A third approach might be to use something like Retain Weapon. That's an active defense you get against attempts to use Break Free to reduce control points on a weapon. In this case, count the attack as successful but telegraphed (+2 to defend against, since you know you are the one compromising your own grapple) and if the defense succeeds, the spent CP is not lost, if it fails, the CP is lost.
==quotes==
===2013===
http://forums.sjgames.com/showpost.php?p=1649556&postcount=6 Douglas Cole suggested that if raw damage from a shove was more than CP it would dislodge the grapple.
===2020===
http://forums.sjgames.com/showpost.php?p=2317642&postcount=13
:if you have someone kickin' around at DX+10 for Skill-20, then you can either rule that as soon as DX hits 0, you're done, regardless of skill, or say as soon as your skill drops below 3, you're done. I've always done the second. 
==see also==
*Cranking It Up
*Quick and Dirty CP
Category:Points