[R] Translating R code + library into Fortran?

[Paul Gilbert]

I have the impression (after only a quick glance at your code, so I may 
have missed something) that you are generating multiple datasets and 
then using them. As a general strategy this does not work very well. You 
will get slightly improved performance with compiled code, but the real 
problem is that you grab too much memory and start swapping, and then 
things will be very slow.

It is better to generate a dataset, use it and save partial results, 
then generate the next dataset, using the same variable name so the 
memory use does not increase. There are examples of this in the dse2 
package in the dse bundle on CRAN. (In fact, you may be able to use some 
of the structure in that package.)

Paul Gilbert

Mike Lawrence wrote:
> Hi all,
> 
> I'm running a monte carlo test of a neural network tool I've developed, 
> and it looks like it's going to take a very long time if I run it in R 
> so I'm interested in translating my code (included below) into something 
> faster like Fortran (which I'll have to learn from scratch). However, as 
> you'll see my code loads the nnet library and uses it quite a bit, and I 
> don't have a good sense of how this impacts the translation process; 
> will I have to translate all the code for the nnet library itself as well?
> 
> Any pointers would be greatly appreciated! Here's my code:
> 
> #This code replicates the simulation performed by Rouder et al (2005),
> #which attempts to test the estimation of weibull distribution parameters
> #from sample data. In this implementation, their HB estimation method is
> #replaced by an iterative neural network approach.
> 
> library(nnet)
> 
> data.gen=function(iterations,min.sample.size,max.sample.size,min.shift,max.shift,min.scale,max.scale,min.shape,max.shape){
>     #set up some collection vectors
>     sample.size=vector(mode="numeric",length=iterations)
>     exp.shift=vector(mode="numeric",length=iterations)
>     exp.scale=vector(mode="numeric",length=iterations)
>     exp.shape=vector(mode="numeric",length=iterations)
>     for(i in 1:iterations){
>         #sample from the parameter space
>         
> sample.size[i]=round(runif(1,min.sample.size,max.sample.size),digits=0)
>         exp.shift[i]=runif(1,min.shift,max.shift)
>         exp.scale[i]=runif(1,min.scale,max.scale)
>         exp.shape[i]=runif(1,min.shape,max.shape)
>         #generate rt data and record summary stats
>         
> obs.rt=rweibull(sample.size[i],exp.shape[i],exp.scale[i])+exp.shift[i]
>         if(i==1){
>             obs.stats=summary(obs.rt)
>         }else{
>             obs.stats=rbind(obs.stats,summary(obs.rt))
>         }
>     }
>     row.names(obs.stats)=c(1:iterations)
>     obs.stats=as.data.frame(obs.stats)
>     
> obs=as.data.frame(cbind(obs.stats,sample.size,exp.shift,exp.scale,exp.shape))
>     
> names(obs)=c("min","q1","med","mean","q3","max","samples","exp.shift","exp.scale","exp.shape")
>     return(obs)
> }
> 
> #set working directory
> setwd("E:/Various Data/NNEst/NetWeibull/Rouder data")
> 
> stadler=read.table("bayest.par")
> names(stadler)=c("exp.shift","exp.scale","exp.shape")
> 
> cell.size=20
> sim.size=600
> #first train initial neural nets
> training.data=data.gen(1e4,cell.size,cell.size,.1,1,.1,1,1,4)
> #train nn.shift with error checking
> ok=F
> while(ok==F){
>     
> nn1.shift=nnet(exp.shift~min+q1+med+mean+q3+max+samples,data=training.data,size=8,linout=T,rang=1e-08,maxit=500,trace=F)
>     cor.shift=predict(nn.shift,training.data[,c(1:7)],type="raw")
>     temp=hist(cor.shift,plot=F)
>     if(length(temp$counts[temp$counts>0])>10){
>         ok=T
>     }
> }
> #train nn.scale with error checking
> ok=F
> while(ok==F){
>     
> nn1.scale=nnet(exp.scale~min+q1+med+mean+q3+max+samples,data=training.data,size=8,linout=T,rang=1e-08,maxit=500,trace=F)
>     cor.scale=predict(nn.scale,training.data[,c(1:7)],type="raw")
>     temp=hist(cor.scale,plot=F)
>     if(length(temp$counts[temp$counts>0])>10){
>         ok=T
>     }
> }
> #train nn.shape with error checking
> ok=F
> while(ok==F){
>     
> nn1.shape=nnet(exp.shape~min+q1+med+mean+q3+max+samples,data=training.data,size=8,linout=T,rang=1e-08,maxit=500,trace=F)
>     cor.shape=predict(nn.shape,training.data[,c(1:7)],type="raw")
>     temp=hist(cor.shape,plot=F)
>     if(length(temp$counts[temp$counts>0])>10){
>         ok=T
>     }
> }
> 
> 
> #run simulation
> obs.stats=matrix(0,80,7)
> ind.shift.err=matrix(0,80,sim.size)
> ind.scale.err=matrix(0,80,sim.size)
> ind.shape.err=matrix(0,80,sim.size)
> group.shift.err=vector(mode="numeric",length=sim.size)
> group.scale.err=vector(mode="numeric",length=sim.size)
> group.shape.err=vector(mode="numeric",length=sim.size)
> for(i in 1:sim.size){
>     for(j in 1:80){
>         
> obs.stats[j,]=c(summary(rweibull(cell.size,stadler$exp.shape[j],stadler$exp.scale[j])+stadler$exp.shift[j]),cell.size)
>     }
>     obs.stats=as.data.frame(obs.stats)
>     names(obs.stats)=c("min","q1","med","mean","q3","max","samples")
>     #estimation iteration 1
>     cor.shift=predict(nn1.shift,obs.stats,type="raw")
>     cor.scale=predict(nn1.scale,obs.stats,type="raw")
>     cor.shape=predict(nn1.shape,obs.stats,type="raw")
>     min.obs.samples=min(obs.stats$samples)
>     max.obs.samples=max(obs.stats$samples)
>     min.shift=quantile(cor.shift,seq(0,1,.05))[2]
>     max.shift=quantile(cor.shift,seq(0,1,.05))[20]
>     min.scale=quantile(cor.scale,seq(0,1,.05))[2]
>     max.scale=quantile(cor.scale,seq(0,1,.05))[20]
>     min.shape=quantile(cor.shape,seq(0,1,.05))[2]
>     max.shape=quantile(cor.shape,seq(0,1,.05))[20]
>     #re-train nets to reduced parameter space
>     
> training.data=data.gen(1e4,min.obs.samples,max.obs.samples,min.shift,max.shift,min.scale,max.scale,min.shape,max.shape)
>     #train nn.shift with error checking
>     ok=F
>     while(ok==F){
>         
> nn2.shift=nnet(exp.shift~min+q1+med+mean+q3+max+samples,data=training.data,size=8,linout=T,rang=1e-08,maxit=500,trace=F)
>         cor.shift=predict(nn2.shift,training.data[,c(1:7)],type="raw")
>         temp=hist(cor.shift,plot=F)
>         if(length(temp$counts[temp$counts>0])>10){
>             ok=T
>         }
>     }
>     #train nn.scale with error checking
>     ok=F
>     while(ok==F){
>         
> nn2.scale=nnet(exp.scale~min+q1+med+mean+q3+max+samples,data=training.data,size=8,linout=T,rang=1e-08,maxit=500,trace=F)
>         cor.scale=predict(nn2.scale,training.data[,c(1:7)],type="raw")
>         temp=hist(cor.scale,plot=F)
>         if(length(temp$counts[temp$counts>0])>10){
>             ok=T
>         }
>     }
>     #train nn.shape with error checking
>     ok=F
>     while(ok==F){
>         
> nn2.shape=nnet(exp.shape~min+q1+med+mean+q3+max+samples,data=training.data,size=8,linout=T,rang=1e-08,maxit=500,trace=F)
>         cor.shape=predict(nn2.shape,training.data[,c(1:7)],type="raw")
>         temp=hist(cor.shape,plot=F)
>         if(length(temp$counts[temp$counts>0])>10){
>             ok=T
>         }
>     }
>     #estimation iteration 2
>     cor.shift=predict(nn2.shift,obs.stats,type="raw")
>     cor.scale=predict(nn2.scale,obs.stats,type="raw")
>     cor.shape=predict(nn2.shape,obs.stats,type="raw")
>     #record error
>     ind.shift.err[,i]=cor.shift-stadler$exp.shift
>     ind.scale.err[,i]=cor.scale-stadler$exp.scale
>     ind.shape.err[,i]=cor.shape-stadler$exp.shape
>     group.shift.err[i]=mean(cor.shift)-mean(stadler$exp.shift)
>     group.scale.err[i]=mean(cor.scale)-mean(stadler$exp.scale)
>     group.shape.err[i]=mean(cor.shape)-mean(stadler$exp.shape)
> }
> 
> results=as.data.frame(rbind(cbind(sd(c(ind.shift.err[,1:162])),sd(c(ind.scale.err[,1:162])),sd(c(ind.shape.err[,1:162]))),cbind(sd(group.shift.err[1:162]),sd(group.scale.err[1:162]),sd(group.shape.err[1:162]))))
> results
> 
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La version française suit le texte anglais.

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