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丢掉分类头，究竟还剩下什么？","sha256":"f031035e407b4865da81a8dd83fe32e638b21752b295b973ca825ae59387ccad","chapter":{"id":"I","title":"学习信号与表示"},"unit":{"id":"i-reuse-and-targets","title":"训练留下什么，训练答案又从哪里来？"},"page":{"id":"reading-opening","title":"丢掉分类头，究竟还剩下什么？","number":1},"sectionTitle":"丢掉分类头，究竟还剩下什么？","currentQuestion":"丢掉分类头，究竟还剩下什么？","sourceSlides":[],"knowledgeBlock":null,"formulas":[],"previousBlock":null,"nextBlock":"b-e736712e3e9e07e8556502a5","prerequisites":[{"id":"b-e736712e3e9e07e8556502a5","url":"#b-e736712e3e9e07e8556502a5","role":"problem-context"}],"relatedBlocks":[]},{"id":"b-e736712e3e9e07e8556502a5","type":"p","scope":"category-head-versus-representation","url":"https://codingai-lec03.pages.dev/course/blocks/category-head-versus-representation.html#b-e736712e3e9e07e8556502a5","content":"本页拆开最终类别判断和中间表示，避免把“预测对了一个类别”当成已经回答了所有问题。","sha256":"26015feda2754cbf7593b55d6aafb5c1f36629a002b1fa01795f4f565f8f4e90","chapter":{"id":"I","title":"学习信号与表示"},"unit":{"id":"i-reuse-and-targets","title":"训练留下什么，训练答案又从哪里来？"},"page":{"id":"reading-opening","title":"丢掉分类头，究竟还剩下什么？","number":1},"sectionTitle":"丢掉分类头，究竟还剩下什么？","currentQuestion":"丢掉分类头，究竟还剩下什么？","sourceSlides":[],"knowledgeBlock":null,"formulas":[],"previousBlock":"b-1b4fa47a53d75aaaf7b0e08f","nextBlock":"b-4298239a681366d61041a22f","prerequisites":[{"id":"b-1b4fa47a53d75aaaf7b0e08f","url":"#b-1b4fa47a53d75aaaf7b0e08f","role":"section-title"}],"relatedBlocks":[]},{"id":"b-4298239a681366d61041a22f","type":"p","scope":"category-head-versus-representation","url":"https://codingai-lec03.pages.dev/course/blocks/category-head-versus-representation.html#b-4298239a681366d61041a22f","content":"一个十分类头可以把 32 维表示压成十个分数。最高分只保留最终决策，完整分数还保留类别间相对偏好；但两者都经过了为原任务学习的投影。若新任务需要原十类名单之外的区分，直接使用这些分数未必合适。","sha256":"80f46bf9ef95db9fbcdc3734c6cc7e132bc4c38cb1855499b861b27c19233523","chapter":{"id":"I","title":"学习信号与表示"},"unit":{"id":"i-reuse-and-targets","title":"训练留下什么，训练答案又从哪里来？"},"page":{"id":"reading-opening","title":"丢掉分类头，究竟还剩下什么？","number":1},"sectionTitle":"丢掉分类头，究竟还剩下什么？","currentQuestion":"丢掉分类头，究竟还剩下什么？","sourceSlides":[],"knowledgeBlock":null,"formulas":[],"previousBlock":"b-e736712e3e9e07e8556502a5","nextBlock":"b-7912e9a9a03bf33c673adcd3","prerequisites":[{"id":"b-1b4fa47a53d75aaaf7b0e08f","url":"#b-1b4fa47a53d75aaaf7b0e08f","role":"section-title"},{"id":"b-e736712e3e9e07e8556502a5","url":"#b-e736712e3e9e07e8556502a5","role":"problem-context"}],"relatedBlocks":[]},{"id":"b-7912e9a9a03bf33c673adcd3","type":"p","scope":"category-head-versus-representation","url":"https://codingai-lec03.pages.dev/course/blocks/category-head-versus-representation.html#b-7912e9a9a03bf33c673adcd3","content":"以数字为例，源任务是 0–9 十分类，新任务是“数字是否大于等于5”。最简单的做法可以先识别数字再合并类别，也可以在中间表示上另学二分类头。这两种使用方式的误差来源不同：前者受原十分类错误约束，后者可以重新组合中间特征。LAB01 采用后者，并明确丢弃原十分类头。","sha256":"85687d40f8274b83ef40cac3f1d86f3623be2391c37f73e7cc0184e6edc689dd","chapter":{"id":"I","title":"学习信号与表示"},"unit":{"id":"i-reuse-and-targets","title":"训练留下什么，训练答案又从哪里来？"},"page":{"id":"reading-opening","title":"丢掉分类头，究竟还剩下什么？","number":1},"sectionTitle":"丢掉分类头，究竟还剩下什么？","currentQuestion":"丢掉分类头，究竟还剩下什么？","sourceSlides":[],"knowledgeBlock":null,"formulas":[],"previousBlock":"b-4298239a681366d61041a22f","nextBlock":"b-57704dd53223a33e06cc7b5a","prerequisites":[{"id":"b-1b4fa47a53d75aaaf7b0e08f","url":"#b-1b4fa47a53d75aaaf7b0e08f","role":"section-title"},{"id":"b-e736712e3e9e07e8556502a5","url":"#b-e736712e3e9e07e8556502a5","role":"problem-context"}],"relatedBlocks":[]},{"id":"b-57704dd53223a33e06cc7b5a","type":"p","scope":"category-head-versus-representation","url":"https://codingai-lec03.pages.dev/course/blocks/category-head-versus-representation.html#b-57704dd53223a33e06cc7b5a","content":"“中间表示更通用”是值得检验的经验判断，不是说它保存了原图的一切。后面的颜色例子会展示，训练目标也可能让中间表示放弃未来有用的差异。","sha256":"6c59a5f364706442d4af4ed926284a34a4ccfd37f156f57c0d0cad464c41f962","chapter":{"id":"I","title":"学习信号与表示"},"unit":{"id":"i-reuse-and-targets","title":"训练留下什么，训练答案又从哪里来？"},"page":{"id":"reading-opening","title":"丢掉分类头，究竟还剩下什么？","number":1},"sectionTitle":"丢掉分类头，究竟还剩下什么？","currentQuestion":"丢掉分类头，究竟还剩下什么？","sourceSlides":[],"knowledgeBlock":null,"formulas":[],"previousBlock":"b-7912e9a9a03bf33c673adcd3","nextBlock":"b-538543d7d545fa147e261d4e","prerequisites":[{"id":"b-1b4fa47a53d75aaaf7b0e08f","url":"#b-1b4fa47a53d75aaaf7b0e08f","role":"section-title"},{"id":"b-e736712e3e9e07e8556502a5","url":"#b-e736712e3e9e07e8556502a5","role":"problem-context"}],"relatedBlocks":[]},{"id":"b-538543d7d545fa147e261d4e","type":"h2","scope":"category-head-versus-representation","url":"https://codingai-lec03.pages.dev/course/blocks/category-head-versus-representation.html#b-538543d7d545fa147e261d4e","content":"## 继续阅读与实验","sha256":"2b9ccef7e1220e2250cceff1abd8bdd736b42f8da5a223f26b029f44b962e807","chapter":{"id":"I","title":"学习信号与表示"},"unit":{"id":"i-reuse-and-targets","title":"训练留下什么，训练答案又从哪里来？"},"page":{"id":"reading-opening","title":"丢掉分类头，究竟还剩下什么？","number":1},"sectionTitle":"丢掉分类头，究竟还剩下什么？","currentQuestion":"丢掉分类头，究竟还剩下什么？","sourceSlides":[],"knowledgeBlock":null,"formulas":[],"previousBlock":"b-57704dd53223a33e06cc7b5a","nextBlock":null,"prerequisites":[{"id":"b-1b4fa47a53d75aaaf7b0e08f","url":"#b-1b4fa47a53d75aaaf7b0e08f","role":"section-title"},{"id":"b-e736712e3e9e07e8556502a5","url":"#b-e736712e3e9e07e8556502a5","role":"problem-context"}],"relatedBlocks":[]}]}