# Exposing quadratic optimizer

**URL:** <https://discourse.mc-stan.org/t/exposing-quadratic-optimizer/4684>\
**Category:** Developers\
**Created:** [June 29, 2018, 1:02am UTC](https://discourse.mc-stan.org/t/exposing-quadratic-optimizer/4684 "2018-06-29T01:02:41Z")\
**Posts on this page:** 1\
**Showing post:** 14

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**Author:** ![charlesm93](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/charlesm93/32/4634_2.png) [@charlesm93](https://discourse.mc-stan.org/u/charlesm93)\
**Post date:** [June 17, 2019, 6:33am UTC](https://discourse.mc-stan.org/t/exposing-quadratic-optimizer/4684/14 "2019-06-17T06:33:39Z")

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There are technical issues for the general implementation of a quadratic optimizer with linear constraints. Yes, we can solve the problem, and yes we can compute derivatives where they exist. But the resulting posterior is non-smooth at the boundaries, which is a problem for HMC. See this [discussion here](https://discourse.mc-stan.org/t/non-smooth-posterior-and-kkt-problem/6281).

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