{"action":"created","issue":{"url":"https://api.github.com/repos/RobotLocomotion/drake/issues/4340","repository_url":"https://api.github.com/repos/RobotLocomotion/drake","labels_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/4340/labels{/name}","comments_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/4340/comments","events_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/4340/events","html_url":"https://github.com/RobotLocomotion/drake/pull/4340","id":193031813,"number":4340,"title":"Added semi-explicit Euler integrator.","user":{"login":"edrumwri","id":2224335,"avatar_url":"https://avatars.githubusercontent.com/u/2224335?v=3","gravatar_id":"","url":"https://api.github.com/users/edrumwri","html_url":"https://github.com/edrumwri","followers_url":"https://api.github.com/users/edrumwri/followers","following_url":"https://api.github.com/users/edrumwri/following{/other_user}","gists_url":"https://api.github.com/users/edrumwri/gists{/gist_id}","starred_url":"https://api.github.com/users/edrumwri/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/edrumwri/subscriptions","organizations_url":"https://api.github.com/users/edrumwri/orgs","repos_url":"https://api.github.com/users/edrumwri/repos","events_url":"https://api.github.com/users/edrumwri/events{/privacy}","received_events_url":"https://api.github.com/users/edrumwri/received_events","type":"User","site_admin":false},"labels":[{"id":353617587,"url":"https://api.github.com/repos/RobotLocomotion/drake/labels/status:%20do%20not%20merge","name":"status: do not merge","color":"e67e22","default":false}],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":3,"created_at":"2016-12-02T04:27:42Z","updated_at":"2016-12-03T00:11:07Z","closed_at":null,"pull_request":{"url":"https://api.github.com/repos/RobotLocomotion/drake/pulls/4340","html_url":"https://github.com/RobotLocomotion/drake/pull/4340","diff_url":"https://github.com/RobotLocomotion/drake/pull/4340.diff","patch_url":"https://github.com/RobotLocomotion/drake/pull/4340.patch"},"body":"Adds semi-explicit Euler integration (thereby adding symplectic integration for Hamiltonian systems) and also stresses the conversions between generalized coordinates and generalized velocities (when the two are distinct).\r\n\r\n*This PR has uncovered a bug in rigid body angular velocity / time derivative of Euler parameter conversions and should not be merged. A proper unit test for rigid body angular velocity / time derivative of Euler parameter is forthcoming (to help address the aforementioned bug), and another PR will address that bug before this merge is attempted.*\n\n<!-- Reviewable:start -->\n---\nThis change is [<img src=\"https://reviewable.io/review_button.svg\" height=\"34\" align=\"absmiddle\" alt=\"Reviewable\"/>](https://reviewable.io/reviews/robotlocomotion/drake/4340)\n<!-- Reviewable:end -->\n"},"comment":{"url":"https://api.github.com/repos/RobotLocomotion/drake/issues/comments/264596396","html_url":"https://github.com/RobotLocomotion/drake/pull/4340#issuecomment-264596396","issue_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/4340","id":264596396,"user":{"login":"edrumwri","id":2224335,"avatar_url":"https://avatars.githubusercontent.com/u/2224335?v=3","gravatar_id":"","url":"https://api.github.com/users/edrumwri","html_url":"https://github.com/edrumwri","followers_url":"https://api.github.com/users/edrumwri/followers","following_url":"https://api.github.com/users/edrumwri/following{/other_user}","gists_url":"https://api.github.com/users/edrumwri/gists{/gist_id}","starred_url":"https://api.github.com/users/edrumwri/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/edrumwri/subscriptions","organizations_url":"https://api.github.com/users/edrumwri/orgs","repos_url":"https://api.github.com/users/edrumwri/repos","events_url":"https://api.github.com/users/edrumwri/events{/privacy}","received_events_url":"https://api.github.com/users/edrumwri/received_events","type":"User","site_admin":false},"created_at":"2016-12-03T00:11:07Z","updated_at":"2016-12-03T00:11:07Z","body":"\n\n\n\nReview status: 0 of 3 files reviewed at latest revision, 7 unresolved discussions, some commit checks failed.\n\n---\n\n*[drake/systems/analysis/semi_explicit_euler_integrator.h, line 21 at r1](https://reviewable.io:443/reviews/robotlocomotion/drake/4340#-KXxsjUvDuelv7ABt4XY:-KY0z5H2KBGo5RO4hap-:bvp637z) ([raw file](https://github.com/robotlocomotion/drake/blob/edbec39d5e01e82d389a42a29ba0b3462f7dc902/drake/systems/analysis/semi_explicit_euler_integrator.h#L21)):*\n<details><summary><i>Previously, sherm1 (Michael Sherman) wrote…</i></summary><blockquote>\n\ntranspose->inverse\n</blockquote></details>\n\nPTAL now- it will be the transpose in the example I described.\n\n---\n\n*[drake/systems/analysis/semi_explicit_euler_integrator.h, line 34 at r1](https://reviewable.io:443/reviews/robotlocomotion/drake/4340#-KXxtBES6ELJgwuYCSd9:-KY1--hRIpEPyciacZc8:b-896fix) ([raw file](https://github.com/robotlocomotion/drake/blob/edbec39d5e01e82d389a42a29ba0b3462f7dc902/drake/systems/analysis/semi_explicit_euler_integrator.h#L34)):*\n<details><summary><i>Previously, sherm1 (Michael Sherman) wrote…</i></summary><blockquote>\n\nBTW, add \"Note that a multibody system will not be Hamiltonian even in the absence of applied velocity-dependent forces, because of Coriolis and gyroscopic forces. These terms can be large in relative coordinate representations like Drake's.\"\n</blockquote></details>\n\nDone.\n\n---\n\n*[drake/systems/analysis/semi_explicit_euler_integrator.h, line 74 at r1](https://reviewable.io:443/reviews/robotlocomotion/drake/4340#-KXxv_704Xo_N2IsY0_5:-KY1-5Zk-xInuowjuoGj:b-896fix) ([raw file](https://github.com/robotlocomotion/drake/blob/edbec39d5e01e82d389a42a29ba0b3462f7dc902/drake/systems/analysis/semi_explicit_euler_integrator.h#L74)):*\n<details><summary><i>Previously, sherm1 (Michael Sherman) wrote…</i></summary><blockquote>\n\nNot sure why the last two sentences are here?\n</blockquote></details>\n\nDone.\n\n---\n\n*[drake/systems/analysis/semi_explicit_euler_integrator.h, line 95 at r1](https://reviewable.io:443/reviews/robotlocomotion/drake/4340#-KXxvsSvl_Xh2N5XNulF:-KXxyawNCzWrr155GE5R:b-896fix) ([raw file](https://github.com/robotlocomotion/drake/blob/edbec39d5e01e82d389a42a29ba0b3462f7dc902/drake/systems/analysis/semi_explicit_euler_integrator.h#L95)):*\n<details><summary><i>Previously, sherm1 (Michael Sherman) wrote…</i></summary><blockquote>\n\nBTW, period.\n</blockquote></details>\n\nDone.\n\n---\n\n*[drake/systems/analysis/semi_explicit_euler_integrator.h, line 97 at r1](https://reviewable.io:443/reviews/robotlocomotion/drake/4340#-KXxvoKilcgcj2LbbKUJ:-KY1-eh96mWS0v2elyXg:barjtim) ([raw file](https://github.com/robotlocomotion/drake/blob/edbec39d5e01e82d389a42a29ba0b3462f7dc902/drake/systems/analysis/semi_explicit_euler_integrator.h#L97)):*\n<details><summary><i>Previously, edrumwri (Evan Drumwright) wrote…</i></summary><blockquote>\n\nGoing to comment on David's PR now :+1: \n</blockquote></details>\n\nDone- put in a TODO to deal with this properly. PTAL.\n\n---\n\n\n*Comments from [Reviewable](https://reviewable.io:443/reviews/robotlocomotion/drake/4340)*\n<!-- Sent from Reviewable.io -->\n"}}
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