Skip to main content

Handling Kernel start. What is a full initialization stack and what place the Autoload has there?


According to: tutorial/WolframSystemSessions



Initialization


On startup, the Wolfram Language kernel does the following:




  • Performs license management operations.





  • Runs Wolfram Language commands specified in any -run options passed to the kernel executable.




  • Runs the Wolfram Language commands in the systemwide initialization file $BaseDirectory/Kernel/init.m.




  • Runs the Wolfram Language commands in the user-specific initialization file $UserBaseDirectory/Kernel/init.m.




  • Loads init.m and Kernel/init.m files in Autoload directories.





  • Begins running the main loop.





So I'd say that packages in Autoload have a freedom to do everything since everything should be already loaded. Yet this example fails:


dir = FileNameJoin[{$UserBaseDirectory, "Autoload", "Fetch", "Kernel"}];

CreateDirectory[dir, CreateIntermediateDirectories -> True]


SetDirectory @ dir;

Export[
 "init.m",
 "Print @ StringTake[URLFetch[\"www.wolfram.com\"], 300]; ", 
 "Text"]

Now quit the Kernel and evaluate something. I only get messages:




URLFetch::invhttp: Couldn't resolve proxy name.


StringTake[$Failed, 300]


Throw::nocatch: Uncaught Throw[False] returned to top level.


Throw::nocatch: Uncaught Throw[False] returned to top level.


Throw::nocatch: Uncaught Throw[False] returned to top level.


General::stop: Further output of Throw::nocatch will be suppressed during this calculation.


Break::nofwd: No enclosing For, While, or Do found for Break[].



While normally this procedure works StringTake[URLFetch["www.wolfram.com"], 300].


Question What's the problem? What more do we need to know about the Initialization stack? Are there any workarounds?



Currently I'm just setting procedure via ScheduledTask to fire 2 seconds later. But that's just silly.


This is not a question about URLFetch (yet good to know this specific problem) but about things I have to know to not be surprised next time.



Answer



Update


Leaving my original answer below for historical purposes, however it only applies up until version 11.1.1.


As of version 11.2.0, the kernel startup initialization has been overhauled and this example (as well as others) now works correctly: placing the URLFetch call in init.m does result in an output like









    
    
    
    Persistence & Initialization framework, and I recommend Roman Maeder's presentation from the 2017 Wolfram Technology Conference.


To make my comment into an answer,



The basic problem, which is not so easy to fix, is that the kernel initialization code has protection against aborts. Since Throw/Catch are implemented internally using this (C code level) abort machinery, they are not functional during initialization, so running any code using them is problematic.


The URLFetch implementation does depend on Catch working correctly, as can be seen from

TracePrint[URLFetch["www.wolfram.com"], _Catch]

Some related questions are the following: (1), (2), (3), (4).

Comments

Post a Comment

Popular posts from this blog

plotting - Filling between two spheres in SphericalPlot3D

Manipulate[ SphericalPlot3D[{1, 2 - n}, {θ, 0, Pi}, {ϕ, 0, 1.5 Pi}, Mesh -> None, PlotPoints -> 15, PlotRange -> {-2.2, 2.2}], {n, 0, 1}] I cant' seem to be able to make a filling between two spheres. I've already tried the obvious Filling -> {1 -> {2}} but Mathematica doesn't seem to like that option. Is there any easy way around this or ... Answer There is no built-in filling in SphericalPlot3D . One option is to use ParametricPlot3D to draw the surfaces between the two shells: Manipulate[ Show[SphericalPlot3D[{1, 2 - n}, {θ, 0, Pi}, {ϕ, 0, 1.5 Pi}, PlotPoints -> 15, PlotRange -> {-2.2, 2.2}], ParametricPlot3D[{ r {Sin[t] Cos[1.5 Pi], Sin[t] Sin[1.5 Pi], Cos[t]}, r {Sin[t] Cos[0 Pi], Sin[t] Sin[0 Pi], Cos[t]}}, {r, 1, 2 - n}, {t, 0, Pi}, PlotStyle -> Yellow, Mesh -> {2, 15}]], {n, 0, 1}]
Post a Comment
Read more

plotting - Plot 4D data with color as 4th dimension

I have a list of 4D data (x position, y position, amplitude, wavelength). I want to plot x, y, and amplitude on a 3D plot and have the color of the points correspond to the wavelength. I have seen many examples using functions to define color but my wavelength cannot be expressed by an analytic function. Is there a simple way to do this? Answer Here a another possible way to visualize 4D data: data = Flatten[Table[{x, y, x^2 + y^2, Sin[x - y]}, {x, -Pi, Pi,Pi/10}, {y,-Pi,Pi, Pi/10}], 1]; You can use the function Point along with VertexColors . Now the points are places using the first three elements and the color is determined by the fourth. In this case I used Hue, but you can use whatever you prefer. Graphics3D[ Point[data[[All, 1 ;; 3]], VertexColors -> Hue /@ data[[All, 4]]], Axes -> True, BoxRatios -> {1, 1, 1/GoldenRatio}]
Post a Comment
Read more

plotting - Mathematica: 3D plot based on combined 2D graphs

I have several sigmoidal fits to 3 different datasets, with mean fit predictions plus the 95% confidence limits (not symmetrical around the mean) and the actual data. I would now like to show these different 2D plots projected in 3D as in but then using proper perspective. In the link here they give some solutions to combine the plots using isometric perspective, but I would like to use proper 3 point perspective. Any thoughts? Also any way to show the mean points per time point for each series plus or minus the standard error on the mean would be cool too, either using points+vertical bars, or using spheres plus tubes. Below are some test data and the fit function I am using. Note that I am working on a logit(proportion) scale and that the final vertical scale is Log10(percentage). (* some test data *) data = Table[Null, {i, 4}]; data[[1]] = {{1, -5.8}, {2, -5.4}, {3, -0.8}, {4, -0.2}, {5, 4.6}, {1, -6.4}, {2, -5.6}, {3, -0.7}, {4, 0.04}, {5, 1.0}, {1, -6.8}, {2, -4.7}, {3, -1.
Post a Comment
Read more