{"action":"created","issue":{"url":"https://api.github.com/repos/hoburg/gpkit/issues/789","repository_url":"https://api.github.com/repos/hoburg/gpkit","labels_url":"https://api.github.com/repos/hoburg/gpkit/issues/789/labels{/name}","comments_url":"https://api.github.com/repos/hoburg/gpkit/issues/789/comments","events_url":"https://api.github.com/repos/hoburg/gpkit/issues/789/events","html_url":"https://github.com/hoburg/gpkit/issues/789","id":169391462,"number":789,"title":"another simple cvxopt unknown example","user":{"login":"whoburg","id":6042395,"avatar_url":"https://avatars.githubusercontent.com/u/6042395?v=3","gravatar_id":"","url":"https://api.github.com/users/whoburg","html_url":"https://github.com/whoburg","followers_url":"https://api.github.com/users/whoburg/followers","following_url":"https://api.github.com/users/whoburg/following{/other_user}","gists_url":"https://api.github.com/users/whoburg/gists{/gist_id}","starred_url":"https://api.github.com/users/whoburg/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/whoburg/subscriptions","organizations_url":"https://api.github.com/users/whoburg/orgs","repos_url":"https://api.github.com/users/whoburg/repos","events_url":"https://api.github.com/users/whoburg/events{/privacy}","received_events_url":"https://api.github.com/users/whoburg/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":{"url":"https://api.github.com/repos/hoburg/gpkit/milestones/9","html_url":"https://github.com/hoburg/gpkit/milestones/GP%20solver%20errors","labels_url":"https://api.github.com/repos/hoburg/gpkit/milestones/9/labels","id":1407411,"number":9,"title":"GP solver errors","description":"","creator":{"login":"bqpd","id":1482776,"avatar_url":"https://avatars.githubusercontent.com/u/1482776?v=3","gravatar_id":"","url":"https://api.github.com/users/bqpd","html_url":"https://github.com/bqpd","followers_url":"https://api.github.com/users/bqpd/followers","following_url":"https://api.github.com/users/bqpd/following{/other_user}","gists_url":"https://api.github.com/users/bqpd/gists{/gist_id}","starred_url":"https://api.github.com/users/bqpd/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bqpd/subscriptions","organizations_url":"https://api.github.com/users/bqpd/orgs","repos_url":"https://api.github.com/users/bqpd/repos","events_url":"https://api.github.com/users/bqpd/events{/privacy}","received_events_url":"https://api.github.com/users/bqpd/received_events","type":"User","site_admin":false},"open_issues":11,"closed_issues":4,"state":"open","created_at":"2015-11-11T21:42:12Z","updated_at":"2016-08-04T20:32:43Z","due_on":null,"closed_at":null},"comments":6,"created_at":"2016-08-04T14:42:19Z","updated_at":"2016-08-04T20:32:43Z","closed_at":"2016-08-04T20:32:43Z","body":"For future analysis, here is a relatively simple but perfectly valid Model that cvxopt cannot solve with default settings.\r\n\r\n```python\r\n\"\"\"Commercial Aircraft Model loosely inspired by TASOPT\"\"\"\r\nimport numpy as np\r\nfrom gpkit import Variable, Model\r\n\r\n\r\nrho = Variable(\"\\\\rho\", 0.4, \"kg/m^3\", \"air density\")\r\na = Variable(\"a\", 300, \"m/s\", \"speed of sound\")\r\nWtemp = Variable(\"W_deleteme\", 1, \"lbf\")\r\ne = Variable(\"e\", 0.85, \"-\", \"Oswald efficiency\")\r\nS = Variable(\"S\", 1300, \"ft^2\", \"wing area\")\r\nA = Variable(\"A\", 9.45, \"-\", \"Aspect ratio\")\r\nWwing = Variable(\"W_{wing}\", \"lbf\", \"wing weight\")\r\nCD = Variable(\"C_D\", \"-\", \"drag coefficient\")\r\nCL = Variable(\"C_L\", \"-\", \"lift coefficient\")\r\nWfuel = Variable(\"W_{fuel}\", 36864.9, \"lbf\", \"fuel weight\")\r\nW = Variable(\"W\", \"lbf\", \"total weight\")\r\nV = Variable(\"V\", \"knots\", \"true airspeed\")\r\nT = Variable(\"T\", \"lbf\", \"thrust\")\r\nM = Variable(\"M\", \"-\", \"Mach number\")\r\nWe = Variable(\"W_e\", 84749.8, \"lbf\", \"empty weight\")\r\nWpay = Variable(\"W_{pay}\", 38700, \"lbf\", \"payload weight\")\r\nWdry = Variable(\"W_{dry}\", \"lbf\", \"dry weight\")\r\n\r\n\r\nconstraints = [W <= 0.5*rho*V**2*CL*S,\r\n               T >= 0.5*rho*V**2*CD*S,\r\n               Wwing >= Wtemp,\r\n               CD >= 0.02 + CL**2/np.pi/e/A,\r\n               W >= Wdry + Wfuel,\r\n               M == V/a,\r\n               Wdry >= We + Wpay + Wwing,\r\n              ]\r\n\r\nm = Model(T/V, constraints)\r\nsol = m.solve()\r\n```\r\n\r\nAs far as I can tell there is nothing wrong with this model. Here are two solver changes that cause it to solve:\r\n\r\n - solve with Mosek (`sol = m.solve(solver=\"mosek\")`)\r\n - solve with cvxopt's ldl kktsolver (`sol = m.solve(kktsolver=\"ldl\")`)\r\n\r\n\r\nAnd for analyzing the cvxopt failure, here are some model changes, each of which causes cvxopt to solve the model with default settings:\r\n\r\n - change the first inequality to an equality (`W == 0.5*rho*V**2*CL*S,`)\r\n - remove the isolated constraint `M == V/a`\r\n - Increase the constant value of Wtemp to 10000\r\n - Remove the last constraint and replace `W >= Wdry + Wfuel` with `W >= We + Wpay + Wwing + Wfuel`"},"comment":{"url":"https://api.github.com/repos/hoburg/gpkit/issues/comments/237674575","html_url":"https://github.com/hoburg/gpkit/issues/789#issuecomment-237674575","issue_url":"https://api.github.com/repos/hoburg/gpkit/issues/789","id":237674575,"user":{"login":"bqpd","id":1482776,"avatar_url":"https://avatars.githubusercontent.com/u/1482776?v=3","gravatar_id":"","url":"https://api.github.com/users/bqpd","html_url":"https://github.com/bqpd","followers_url":"https://api.github.com/users/bqpd/followers","following_url":"https://api.github.com/users/bqpd/following{/other_user}","gists_url":"https://api.github.com/users/bqpd/gists{/gist_id}","starred_url":"https://api.github.com/users/bqpd/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bqpd/subscriptions","organizations_url":"https://api.github.com/users/bqpd/orgs","repos_url":"https://api.github.com/users/bqpd/repos","events_url":"https://api.github.com/users/bqpd/events{/privacy}","received_events_url":"https://api.github.com/users/bqpd/received_events","type":"User","site_admin":false},"created_at":"2016-08-04T20:32:43Z","updated_at":"2016-08-04T20:32:43Z","body":"Smells like success to me."}}
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