Re: Issue with ParallelTable and AstronomicalData
- To: mathgroup at smc.vnet.net
- Subject: [mg116226] Re: Issue with ParallelTable and AstronomicalData
- From: Patrick Scheibe <pscheibe at trm.uni-leipzig.de>
- Date: Mon, 7 Feb 2011 06:06:39 -0500 (EST)
Hi, gives the same results here (Linux-x86-64) but this anyway a very bad idea: Say you move from New York to Germany and you send all your stuff on a big ship to reassemble it after two weeks journey in your new flat in Germany. Pretty long time you think, but you come up with a brilliant idea: Lets to all this work in parallel! So you send not only one ship, but say 4 ships and distribute you stuff on them and you reassemble not alone but with 3 other workers.. Do you see where the bottleneck is and why this won't be really faster? I'm pretty sure that AstronomicalData[..] accesses your hard-drive to fetch the data and if so, you shouldn't expect a speedup by a parallel execution. Cheers Patrick On Sat, 2011-02-05 at 05:44 -0500, Thomas Melehan wrote: > Group: > > The the only difference in the following two modules is the use of > ParallelTable in one and Table in the other. For some strange reason > they give different results. I tried to DistributeDefinitions > [AstronomicalData], with no impact. Any ideas? > > > I am using Mathematica 8 on Mac OSX 10.6.6 > > > > > Module[{date, month, day, =CE=B1, =CE=B3Sun, testData}, > > ParallelTable[ > > date = DateList[{2010, ToExpression[month], ToExpression[day], > ToExpression[hour]}, TimeZone -> -5]; > =CE=B1 = Max[AstronomicalData["Sun", {"Altitude", date}, TimeZone -> -5] , > 0] Degree ; > =CE=B3Sun = AstronomicalData["Sun", {"Azimuth", date}, TimeZone -> -5] Degree; > testData = > AstronomicalData["Sun", {#, date}] Degree & /@ {"Azimuth", "Altitude"}; > > {date, =CE=B3Sun, =CE=B1, testData, month, day, hour} > > , {month, {"01"}}, {day, {"15"}}, {hour, {"08", "09"}}] > > ] > > > Module[{date, month, day, =CE=B1, =CE=B3Sun, testData}, > > Table[ > > date = DateList[{2010, ToExpression[month], ToExpression[day], > ToExpression[hour]}, TimeZone -> -5]; > =CE=B1 = Max[AstronomicalData["Sun", {"Altitude", date}, TimeZone -> -5] , > 0] Degree ; > =CE=B3Sun = AstronomicalData["Sun", {"Azimuth", date}, TimeZone -> -5] Degree; > testData = > AstronomicalData["Sun", {#, date}] Degree & /@ {"Azimuth", "Altitude"}; > > {date, =CE=B3Sun, =CE=B1, testData, month, day, hour} > > , {month, {"01"}}, {day, {"15"}}, {hour, {"08", "09"}}] > > ] >