Skip to main content

evaluation - Get the current iteration count


I would like to be able to get the current iteration count, the one that if exceeds $IterationLimit makes the evaluation stop.


After not finding a magical variable that stores this value, or a magical built-in that retrieves it, I thought about TraceScan.



According to the documentation of $IterationLimit,



$IterationLimit gives an upper limit on the length of any list that can be generated by Trace

However, a quick test shows that this is not so simple. Let's define


ClearAll[f]
f[i_] := f[i - 1]
f[0] := "Yeah"

Now,



Block[{$IterationLimit = 20},
Trace[f[18]] // Length//Print;
Trace[f[18], TraceDepth -> 1] // Length//Print;
f[18]
]

prints 56 and 38 respectively, while f[18]'s evaluation finishes successfully.


Looking at the output of the last trace, we see that the before and after argument evaluation are being traced. So,


Trace[f[3], TraceDepth -> 1]   
(* {f[3],f[3-1],f[2],f[2-1],f[1],f[1-1],f[0],Yeah} *)


Notice that the "two outputs per iteration" rule doesn't hold if we add a definition like f[3]=f[1], in which case


Trace[f[5], TraceDepth -> 1]
(* {f[5],f[5-1],f[4],f[4-1],f[3],f[1],f[1-1],f[0],Yeah} *)

If this happened, a hacky workround could exist along the lines of


SetAttributes[trackIterations, HoldFirst];
trackIterations[code_] := Block[{iterationCounter = 0},
TraceScan[iterationCounter += 1/2, code, TraceDepth -> 1]
]


Question


How can I get that counter, or alternatively, how can I make Trace only trace once each iteration?




Comments

Popular posts from this blog

plotting - How to draw lines between specified dots on ListPlot?

I would like to create a plot where I have unconnected dots and some connected. So far, I have figured out how to draw the dots. My code is the following: ListPlot[{{1, 1}, {2, 2}, {3, 3}, {4, 4}, {1, 4}, {2, 5}, {3, 6}, {4, 7}, {1, 7}, {2, 8}, {3, 9}, {4, 10}, {1, 10}, {2, 11}, {3, 12}, {4,13}, {2.5, 7}}, Ticks -> {{1, 2, 3, 4}, None}, AxesStyle -> Thin, TicksStyle -> Directive[Black, Bold, 12], Mesh -> Full] I have thought using ListLinePlot command, but I don't know how to specify to the command to draw only selected lines between the dots. Do have any suggestions/hints on how to do that? Thank you. Answer One possibility would be to use Epilog with Line : ListPlot[ {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {1, 4}, {2, 5}, {3, 6}, {4, 7}, {1, 7}, {2, 8}, {3, 9}, {4, 10}, {1, 10}, {2, 11}, {3, 12}, {4, 13}, {2.5, 7}}, Ticks -> {{1, 2, 3, 4}, None}, AxesStyle -> Thin, TicksStyle -> Directive[Black, Bold, 12], Mesh -> Full, Epilog -> { Line[ ...

dynamic - How can I make a clickable ArrayPlot that returns input?

I would like to create a dynamic ArrayPlot so that the rectangles, when clicked, provide the input. Can I use ArrayPlot for this? Or is there something else I should have to use? Answer ArrayPlot is much more than just a simple array like Grid : it represents a ranged 2D dataset, and its visualization can be finetuned by options like DataReversed and DataRange . These features make it quite complicated to reproduce the same layout and order with Grid . Here I offer AnnotatedArrayPlot which comes in handy when your dataset is more than just a flat 2D array. The dynamic interface allows highlighting individual cells and possibly interacting with them. AnnotatedArrayPlot works the same way as ArrayPlot and accepts the same options plus Enabled , HighlightCoordinates , HighlightStyle and HighlightElementFunction . data = {{Missing["HasSomeMoreData"], GrayLevel[ 1], {RGBColor[0, 1, 1], RGBColor[0, 0, 1], GrayLevel[1]}, RGBColor[0, 1, 0]}, {GrayLevel[0], GrayLevel...

list manipulation - Selecting multiple columns from a matrix?

Sample data: data = { {{2013, 1, 1}, 24.13, 167.67, 231.82}, {{2013, 1, 2}, 32.15, 170.92, 225.99}, {{2013, 1, 3}, 35.43, 172.68, 221.67}, {{2013, 1, 4}, 36.73, 173.05, 218.32}, {{2013, 1, 5}, 58.19, 165.96, 197.05}, {{2013, 1, 6}, 69.99, 163.50, 187.52}, {{2013, 1, 7}, 71.37, 154.21, 175.58}, {{2013, 1, 8}, 72.51, 149.66, 163.25}}; I want a DateListPlot with three graphs, so for a matrix formed by columns 1 and 2, one for columns 1 and 3, and 1 for columns 1 and 4. At the moment I'm using this code: data2 = Transpose[{data[[All, 1]], data[[All, 2]]}]; data3 = Transpose[{data[[All, 1]], data[[All, 3]]}]; data4 = Transpose[{data[[All, 1]], data[[All, 4]]}]; DateListPlot[{data2, data3, data4}, Joined -> True, Filling -> {3 -> {1}}] but I have a hunch that this can be done more efficiently. I don't like the Transpose s in particular. Any ideas? edit (for extra credit) What if I need to multiply the second column by 2, which in my solution is simp...