There is an issue with Manipulate in which it updates its argument twice in V10

Question

I have asked this question before (here) and I thought that the issue is only when moving the Notebook window.

It appears that Manipulate is working in weird manner.

data = RandomReal[100, {10000, 10}];
Manipulate[
 Grid[{{RandomReal[100]}, {ListPlot[data[[;; , i]], 
     PlotLabel -> RandomReal[100], ImageSize -> 400, 
     PlotStyle -> Hue[RandomReal[1]]]}}], {i, 1, 10, 1}]

Manipulate updates its argument twice even if the window is static without moving.

This is really creates a big problem for me and all codes done in V9 are very slow running in V10.

Any help will be highly appreciated.

Update:

the suggested solution by Sjoerd C. de Vries works in this case but not in general as shown in this example:

Manipulate[
 a = Log[i];
 Grid[{{RandomReal[100]}, {ListPlot[a data[[;; , i]], 
     PlotLabel -> RandomReal[100], ImageSize -> 400, 
     PlotStyle -> Hue[RandomReal[1]], 
     PerformanceGoal -> "Quality"]}}], {i, 2, 10, 1}]

Thank you

Answer 1

It seems to me that this double evaluation is simply part of the mechanism of Manipulate. When the slider is dragged one expression is displayed, and when it is released another is displayed. I described this a bit in PolarPlot render oddities but here is another example. I use ControlActive to make the behavior explicit but same action is implicit without it.

Manipulate[ControlActive["foo", RandomReal[{0, i}]], {i, 2, 10, 1}]

Observe that while the slider is being dragged "foo" is displayed rather than a random number. When the slider is released the second expression is evaluated and displayed as a random number. If you wish to avoid the second evaluation you can store a copy of the result of the first evaluation and display it at that time:

DynamicModule[{x},
  Manipulate[a = Log[i];
    ControlActive[
      x = Grid[{{RandomReal[100]},
           {ListPlot[a data[[;; , i]], PlotLabel -> RandomReal[100], 
            ImageSize -> 400, PlotStyle -> Hue[RandomReal[1]]]}}],
      x
    ],
    {i, 2, 10, 1},
    TrackedSymbols :> {i}
  ]
]

Edit: added TrackedSymbols :> {i} to improve evaluation behavior.
See Michael's comment below for caveats.

---

Update

The method above has problems with quick clicks on the slider. This seems to solve the problem but I have only tested it briefly:

Manipulate[
  Block[{$ControlActiveSetting = False},
    a = Log[i];
    Grid[{{RandomReal[100]}, {ListPlot[a data[[;; , i]], PlotLabel -> RandomReal[100], 
      ImageSize -> 400, PlotStyle -> Hue[RandomReal[1]]]}}]
  ],
  {i, 2, 10, 1}, 
  TrackedSymbols :> {i}
]

Answer 2

Edit

This is the workaround I've found :

data = RandomReal[100, {10000, 10}];

Manipulate[
 Block[{$PerformanceGoal = "Quality", a}, a = Log[i];
  Grid[{{RandomReal[100]}, {ListPlot[a data[[;; , i]], 
      PlotLabel -> RandomReal[100], ImageSize -> 400, 
      PlotStyle -> Hue[RandomReal[1]], 
      PerformanceGoal -> "Quality"]}}]], {i, 2, 10, 1}]

a (which is a function of i) must be defined as a local value inside the Block and then set to its value.

It seems everything works as it should be (click and dragging the slider, click on buttons +/-)

---

Previous

As indicated the problem can be solved with the option $PerformanceGoal, but as the OP showed it is not enough here just to set the option inside ListPlot.

Let's take a simpler example :

Manipulate[i + 1; 
 ListPlot[RandomReal[10, 100], PlotStyle -> {Hue[RandomReal[]]}, 
  PlotLabel -> $PerformanceGoal, PerformanceGoal -> "Quality"], {i, 1, 10, 1}]

As a label, i just display the $PerformanceGoal and it is clear that when you click the + button, the plot is displayed : the first time with $PerformanceGoal set to "Speed" and the second time set to "Quality". Setting the option inside ListPlot seems to have no effect.

The problem is solved if you set $PerformanceGoal inside a Block. Here:

Manipulate[i + 1; 
 Block[{$PerformanceGoal = "Quality"}, 
  ListPlot[RandomReal[10, 100], PlotStyle -> {Hue[RandomReal[]]}, 
   PlotLabel -> $PerformanceGoal]], {i, 1, 10, 1}]

Update

HOWEVER, this is not the end of the story, because as commented the OP, the previous solution won't work for the particular case at the end of his post. My example was too simple : there is no variable i inside the ListPlot.

Let's make something more complicated, just multiply the RandomReal list by i (inside ListPlot):

Manipulate[i + 1;
 Block[{$PerformanceGoal = "Quality"}, 
  ListPlot[i*RandomReal[10, 10000], PlotStyle -> {Hue[RandomReal[]]}, 
   PlotLabel -> $PerformanceGoal]], {i, 1, 10, 1}]

You can check that will work too.

BUT if you set a=i then multiply RandomReal by a, now it won't work:
(note that I added a Pause inside the Block in order to see better the evaluations, it does not modify the problem)

Manipulate[i + 1; a = i;
 Block[{$PerformanceGoal = "Quality"}, Pause[0.5];
  ListPlot[a*RandomReal[10, 20000], PlotStyle -> {Hue[RandomReal[]]}, 
   PlotLabel -> $PerformanceGoal]], {i, 1, 10, 1}]

Note also that, though the $PerformanceGoal changes no more, you can clearly see that the code is evaluated twice, whether the slide is moved by clicking (not dragging), or the + or - buttons are clicked.

unless you do:

Manipulate[i + 1;
 Block[{$PerformanceGoal = "Quality", a}, Pause[0.5];
  a = i; ListPlot[a*RandomReal[10, 20000], 
   PlotStyle -> {Hue[RandomReal[]]}, 
   PlotLabel -> $PerformanceGoal]], {i, 1, 10, 1}]

Other strange behaviours

I have played a little bit with all this, and I also observed some other strange behaviours :

You can even have three evaluations if you do that :

Manipulate[a = i; Pause[0.5]; 
 Grid[{{RandomReal[100]}, {ListPlot[a*RandomReal[10, 100], 
     PlotLabel -> RandomReal[100], ImageSize -> 400, 
     PlotStyle -> Hue[RandomReal[1]]]}}], {i, 1, 10, 1}]

or if you put the same code into two separate cells, just one beneath the over, and then if you change the position of one slider, this is what happens :

Manipulate[i + 1; a = i;
 ListPlot[a*RandomReal[10, 100], PlotStyle -> {Hue[RandomReal[]]}, 
  PlotLabel -> $PerformanceGoal, PerformanceGoal -> "Quality"], {i, 1,
   10, 1}]

and the same

Manipulate[i + 1; a = i;
 ListPlot[a*RandomReal[10, 100], PlotStyle -> {Hue[RandomReal[]]}, 
  PlotLabel -> $PerformanceGoal, PerformanceGoal -> "Quality"], {i, 1,
   10, 1}]

gives