Monthly Archives: August 2018

Finding core-dump file

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In a new server, my program got ‘core dump’. But I haven’t found the core-dump file in the current directory as usual. First I checked the ‘ulimit’ configuration:

Seems ok. The system will generate core-dump file when the program crashed. But where is it? Eventually, I found out the… Read more »

Source code analysis for Autograd

Autograd is a convenient tool to automatically differentiate native Python and Numpy code. Let’s look at an example first:

The result is 3.2 f(x) = sqaure(x) + 1, its derivative is 2*x, so the result is correct. Function grad() actually return a ‘function object’, which is ‘grad_f’. When we… Read more »

Prediction of Red Wine Quality

In Kaggle platform, there is an example dataset about Quality of Red Wine. I wrote some code for it by using scikit-learn and pandas:

The results reported by snippet above:

Looks the most important feature to predict quality of red wine is ‘alcohol’. Intuitively, right?

Use PCA (Principal Component Analysis) to blur color image

I wrote an example of blurring color picture by using PCA from scikit-learn:

But it reports

The correct solution is transforming image to 2 dimensions shape, and inverse transform it after PCA:

It works very well now. Let’s see the original image and blurring image: Original Image… Read more »