tag:blogger.com,1999:blog-4401555280825766585.post1127692291229736199..comments2023-07-21T04:50:56.062-04:00Comments on Life of a Computer Scientist: Cost estimate for large projectLikai Liuhttp://www.blogger.com/profile/06372207357661600589noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-4401555280825766585.post-7202635358582180552010-05-15T12:13:21.780-04:002010-05-15T12:13:21.780-04:00Some clarification...
The linear model predicts p...Some clarification...<br /><br />The linear model predicts productivity and cost relation to grow like a linear equation an + b where n is the productivity, e.g. with a cost model "n * 2 + 20" we have:<br /><br />productivity: 10, 20, 30, 40, 50<br />cost: 40, 60, 80, 100, 120<br />cost per unit: 4, 3, 2.67, 2.5, 2.4<br /><br />Cost per unit simply divides the total cost by the number of units of productivity. This gives the illusion of scale, where more productivity decreases cost per unit. But I'm arguing that the linear model is overly naive. The model I propose is linear-logarithmic, so a cost model would be an * logn + bn + c, e.g. with a cost model "2n * logn + 20" we have:<br /><br />productivity: 10, 20, 30, 40, 50<br />cost: 40, 72, 109, 148, 189<br />cost per unit of productivity: 4, 3.6, 3.63, 3.7, 3.78<br /><br />You can see that the sweet spot is when the productivity is around 20. The more productivity you try to achieve, cost per unit goes up again.<br /><br />I postulate this theory after observing how a lot of large projects seem to lose cost effectiveness at a large scale, using things we learn in computer science. Computer science is less about computers, but more about model of computation, and how to predict performance. That's why it's kind of hard to explain what we do. But if you treat human beings as a computer and the society as a model of computation, then computer science can explain economy very well.Likai Liuhttps://www.blogger.com/profile/06372207357661600589noreply@blogger.com