{"id":659097,"date":"2020-05-14T11:11:45","date_gmt":"2020-05-14T18:11:45","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/?post_type=msr-research-item&#038;p=659097"},"modified":"2025-09-02T07:31:52","modified_gmt":"2025-09-02T14:31:52","slug":"a-reduction-from-reinforcement-learning-to-no-regret-online-learning","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/a-reduction-from-reinforcement-learning-to-no-regret-online-learning\/","title":{"rendered":"A Reduction from Reinforcement Learning to No-Regret Online Learning"},"content":{"rendered":"<p>We present a reduction from reinforcement learning (RL) to no-regret online learning based on the saddle-point formulation of RL, by which &#8220;any&#8221; online algorithm with sublinear regret can generate policies with provable performance guarantees. This new perspective decouples the RL problem into two parts: regret minimization and function approximation. The first part admits a standard online-learning analysis, and the second part can be quantified independently of the learning algorithm. Therefore, the proposed reduction can be used as a tool to systematically design new RL algorithms. We demonstrate this idea by devising a simple RL algorithm based on mirror descent and the generative-model oracle. For any\u00a0<span id=\"MathJax-Element-1-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-1\" class=\"math\"><span id=\"MathJax-Span-2\" class=\"mrow\"><span id=\"MathJax-Span-3\" class=\"mi\">\u03b3<\/span><\/span><\/span><\/span>-discounted tabular RL problem, with probability at least\u00a0<span id=\"MathJax-Element-2-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-4\" class=\"math\"><span id=\"MathJax-Span-5\" class=\"mrow\"><span id=\"MathJax-Span-6\" class=\"mn\">1<\/span><span id=\"MathJax-Span-7\" class=\"mo\">\u2212<\/span><span id=\"MathJax-Span-8\" class=\"mi\">\u03b4<\/span><\/span><\/span><\/span>, it learns an\u00a0<span id=\"MathJax-Element-3-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-9\" class=\"math\"><span id=\"MathJax-Span-10\" class=\"mrow\"><span id=\"MathJax-Span-11\" class=\"mi\">\u03f5<\/span><\/span><\/span><\/span>-optimal policy using at most\u00a0<span id=\"MathJax-Element-4-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-12\" class=\"math\"><span id=\"MathJax-Span-13\" class=\"mrow\"><span id=\"MathJax-Span-14\" class=\"texatom\"><span id=\"MathJax-Span-15\" class=\"mrow\"><span id=\"MathJax-Span-16\" class=\"munderover\"><span id=\"MathJax-Span-17\" class=\"mi\">O<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-19\" class=\"mrow\"><span id=\"MathJax-Span-20\" class=\"mo\">(<\/span><span id=\"MathJax-Span-21\" class=\"mfrac\"><span id=\"MathJax-Span-22\" class=\"mrow\"><span id=\"MathJax-Span-23\" class=\"texatom\"><span id=\"MathJax-Span-24\" class=\"mrow\"><span id=\"MathJax-Span-25\" class=\"mo\">|<\/span><\/span><\/span><span id=\"MathJax-Span-26\" class=\"texatom\"><span id=\"MathJax-Span-27\" class=\"mrow\"><span id=\"MathJax-Span-28\" class=\"mi\">S<\/span><\/span><\/span><span id=\"MathJax-Span-29\" class=\"texatom\"><span id=\"MathJax-Span-30\" class=\"mrow\"><span id=\"MathJax-Span-31\" class=\"mo\">|<\/span><\/span><\/span><span id=\"MathJax-Span-32\" class=\"texatom\"><span id=\"MathJax-Span-33\" class=\"mrow\"><span id=\"MathJax-Span-34\" class=\"mo\">|<\/span><\/span><\/span><span id=\"MathJax-Span-35\" class=\"texatom\"><span id=\"MathJax-Span-36\" class=\"mrow\"><span id=\"MathJax-Span-37\" class=\"mi\">A<\/span><\/span><\/span><span id=\"MathJax-Span-38\" class=\"texatom\"><span id=\"MathJax-Span-39\" class=\"mrow\"><span id=\"MathJax-Span-40\" class=\"mo\">|<\/span><\/span><\/span><span id=\"MathJax-Span-41\" class=\"mi\">log<\/span><span id=\"MathJax-Span-42\" class=\"mo\"><\/span><span id=\"MathJax-Span-43\" class=\"mo\">(<\/span><span id=\"MathJax-Span-44\" class=\"mfrac\"><span id=\"MathJax-Span-45\" class=\"mn\">1\/<\/span><span id=\"MathJax-Span-46\" class=\"mi\">\u03b4<\/span><\/span><span id=\"MathJax-Span-47\" class=\"mo\">) \/ <\/span><\/span><span id=\"MathJax-Span-48\" class=\"mrow\"><span id=\"MathJax-Span-49\" class=\"mo\">(<\/span><span id=\"MathJax-Span-50\" class=\"mn\">1<\/span><span id=\"MathJax-Span-51\" class=\"mo\">\u2212<\/span><span id=\"MathJax-Span-52\" class=\"mi\">\u03b3<\/span><span id=\"MathJax-Span-53\" class=\"msubsup\"><span id=\"MathJax-Span-54\" class=\"mo\">)^<\/span><span id=\"MathJax-Span-55\" class=\"mn\">4<\/span><\/span><span id=\"MathJax-Span-56\" class=\"msubsup\"><span id=\"MathJax-Span-57\" class=\"mi\">\u03f5^<\/span><span id=\"MathJax-Span-58\" class=\"mn\">2<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-59\" class=\"mo\">)<\/span><\/span><\/span><\/span><\/span>\u00a0samples. Furthermore, this algorithm admits a direct extension to linearly parameterized function approximators for large-scale applications, with computation and sample complexities independent of\u00a0<span id=\"MathJax-Element-5-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-60\" class=\"math\"><span id=\"MathJax-Span-61\" class=\"mrow\"><span id=\"MathJax-Span-62\" class=\"texatom\"><span id=\"MathJax-Span-63\" class=\"mrow\"><span id=\"MathJax-Span-64\" class=\"mo\">|<\/span><\/span><\/span><span id=\"MathJax-Span-65\" class=\"texatom\"><span id=\"MathJax-Span-66\" class=\"mrow\"><span id=\"MathJax-Span-67\" class=\"mi\">S<\/span><\/span><\/span><span id=\"MathJax-Span-68\" class=\"texatom\"><span id=\"MathJax-Span-69\" class=\"mrow\"><span id=\"MathJax-Span-70\" class=\"mo\">|<\/span><\/span><\/span><\/span><\/span><\/span>,<span id=\"MathJax-Element-6-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-71\" class=\"math\"><span id=\"MathJax-Span-72\" class=\"mrow\"><span id=\"MathJax-Span-73\" class=\"texatom\"><span id=\"MathJax-Span-74\" class=\"mrow\"><span id=\"MathJax-Span-75\" class=\"mo\">|<\/span><\/span><\/span><span id=\"MathJax-Span-76\" class=\"texatom\"><span id=\"MathJax-Span-77\" class=\"mrow\"><span id=\"MathJax-Span-78\" class=\"mi\">A<\/span><\/span><\/span><span id=\"MathJax-Span-79\" class=\"texatom\"><span id=\"MathJax-Span-80\" class=\"mrow\"><span id=\"MathJax-Span-81\" class=\"mo\">|<\/span><\/span><\/span><\/span><\/span><\/span>, though at the cost of potential approximation bias.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>We present a reduction from reinforcement learning (RL) to no-regret online learning based on the saddle-point formulation of RL, by which &#8220;any&#8221; online algorithm with sublinear regret can generate policies with provable performance guarantees. This new perspective decouples the RL problem into two parts: regret minimization and function approximation. The first part admits a standard [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","msr-author-ordering":null,"msr_publishername":"","msr_publisher_other":"","msr_booktitle":"","msr_chapter":"","msr_edition":"","msr_editors":"","msr_how_published":"","msr_isbn":"","msr_issue":"","msr_journal":"","msr_number":"","msr_organization":"","msr_pages_string":"","msr_page_range_start":"","msr_page_range_end":"","msr_series":"","msr_volume":"","msr_copyright":"","msr_conference_name":"International Conference on Artificial Intelligence and 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