# How to make the ProgressIndicator for ParallelDo more efficient

I am trying to keep track of a calculation for visualization purposes ( I want to show to the user that calculation is in progress) . For that I use ProgressIndicator. However inside the paralleldo keeping track of the variable for the indicator makes the calculation much slower with respect to no-indicator. I wrote a "toy code" that mimics what I am doing. In this toy-code I am simply multiplying two arrays over and over again. Is there a way to make d run only in the main kernel and I simply multiply the with number of kernels, this will give me a rough idea.

myDummyF[nd_, np_] := Module[{mat, mat2, aI},

ns = 200;
mat = SetAccuracy[RandomReal[{-100, 100}, ns], nd];
mat2 = SetAccuracy[RandomReal[{-200, 200}, ns], nd];
d = 0;
aI = ConstantArray[0, np];
SetSharedVariable[aI, d];

Time = AbsoluteTiming[
If[nd <= 16,
Monitor[Do[
If[iC == 2, Print["Do Loop"]];
aI[[iC]] = SetAccuracy[mat.(mat2/iC^0.5), nd], {iC, np}],
ProgressIndicator[Dynamic[iC/np]]],
Monitor[ParallelDo[d++;
If[iC == 2, Print[" ParallelDo Loop"]];
aI[[iC]] = SetAccuracy[mat.(mat2/iC^0.5), nd];
, {iC, np}],
ProgressIndicator[Dynamic[d/np]]]]];

Print["Do loop time = ", Time[[1]], ", np = ", np, ", nd = ", nd];
aInum = Apply[Plus, (aI/np)];
Print["Total = ", aInum];
Return[aInum]];
np = 1000;
nd = 30;
myDummyF[nd, np];


For do loop (not the parallel one) there is not performance issue. I know the that the performance hit coming from the overhead of carrying d. Is there another way of doing this? I don't need to keep track exactly just an idea would be fine.

Below is the same code without process indicator:

myDummyF[nd_, np_] := Module[{mat, mat2, aI},

ns = 200;
mat = SetAccuracy[RandomReal[{-100, 100}, ns], nd];

mat2 = SetAccuracy[RandomReal[{-200, 200}, ns], nd];

aI = ConstantArray[0, np];
SetSharedVariable[aI];
Time = AbsoluteTiming[
If[nd <= 16,
Do[
If[iC == 2, Print["---------------------"]];
If[iC == 2, Print["Do Loop", " nd= ", nd, " np= ", np]];
aI[[iC]] = SetAccuracy[mat.(mat2/iC^0.5), nd], {iC, np}],
ParallelDo[
If[iC == 2, Print["---------------------"]];
If[iC == 2,
Print[" ParallelDo Loop", " nd= ", nd, " np= ", np]];
aI[[iC]] = SetAccuracy[mat.(mat2/iC^0.5), nd], {iC, np}]]];
Print["Do loop time = ", Time[[1]]];
aInum = Apply[Plus, (aI/np)];
Print["Total = ", aInum];
Print["---------------------"];
Return[aInum]];
np = 1000;
nd = 30;
myDummyF[nd, np];

• Sometimes it is not worth to track an exact stage of the calculation and just show ProgressIndicator[ Appearance -> "Indeterminate"] before it is finished. p.s. are you sure every part of this code is essential to reproduce the problem?
– Kuba
Aug 11, 2016 at 17:20
• I gave the detail to show the performance difference between do and paralleldo. That is why I gave the details. With your suggestion, the progress indicator fills (%100) and after that calculation starts. That might be misleading. Is there a way to make d run only in the main kernel? Aug 11, 2016 at 18:11
• Did you check the answers to the following questions? (1548), (15369), (74230), (86049) Aug 15, 2016 at 18:22
• @Karsten7. I did not see them before, I checked them. I think still the same suffering from the time of keep track of an variable in each kernel. Thnx Aug 17, 2016 at 13:57

I didn't want to bother about handling nd <= 16 as an extra condition and made some additional changes that increase the performance.

np = 1000;
nd = 30;


First the function without a ProgressIndicator as a reference:

dummyFKnoPI[nd_, np_] := Module[{mat, mat2, aI, ns = 200, time, aInum},
mat = SetAccuracy[RandomReal[{-100, 100}, ns], nd];
mat2 = SetAccuracy[RandomReal[{-200, 200}, ns], nd];
aI = ConstantArray[0, np];

time = AbsoluteTiming[
Print[" Parallel Loop"];
aI = ParallelTable[
SetAccuracy[mat.(mat2/iC^0.5), nd],
{iC, np}];
];
Print["Loop time = ", time[[1]], ", np = ", np, ", nd = ", nd];
aInum = Apply[Plus, (aI/np)];
Print["Total = ", aInum];
aInum];

dummyFKnoPI[nd, np*100];

 Parallel Loop
Loop time = 4.30922, np = 100000, nd = 30
Total = -392.25069339023950901292892012862


Now the function with a ProgressIndicator, but minimal inter kernel communication overload:

dummyFK[nd_, np_] := Module[{mat, mat2, aI, ns = 200, d = 0, dl, time, aInum},
mat = SetAccuracy[RandomReal[{-100, 100}, ns], nd];
mat2 = SetAccuracy[RandomReal[{-200, 200}, ns], nd];
aI = ConstantArray[0, np];

SetSharedVariable[d];
ParallelEvaluate[dl = 0];

time = AbsoluteTiming[
Print[" Parallel Loop"];
Monitor[
aI = ParallelTable[
If[Mod[dl++, 1000] == 0, d += 1000];
SetAccuracy[mat.(mat2/iC^0.5), nd],
{iC, np}];,
ProgressIndicator[d/np]
]
];
Print["Loop time = ", time[[1]], ", np = ", np, ", nd = ", nd];
aInum = Apply[Plus, (aI/np)];
Print["Total = ", aInum];
aInum];

dummyFK[nd, np*100];

 Parallel Loop
Loop time = 4.5777, np = 100000, nd = 30
Total = -457.35153371159704445886973189772


When using d++ instead of If[Mod[dl++, 1000] == 0, d += 1000] the Loop time is 309.525.

• Thank you for the help. I just made a little modification to scale the step of d with respect to np. Instead of directly putting 1000 , I did Ceilling[nd/75] this makes the lack between %100 status bar and calculation to finish to minimal. Aug 21, 2016 at 19:22