R与12个核并行

Question

我最近买了一台12核的新电脑。

我尝试使用foreach包和以下命令运行R脚本：

> sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United Kingdom.1252 
[2] LC_CTYPE=English_United Kingdom.1252   
[3] LC_MONETARY=English_United Kingdom.1252
[4] LC_NUMERIC=C                           
[5] LC_TIME=English_United Kingdom.1252    

attached base packages:
 [1] parallel  splines   grid      stats     graphics  grDevices utils    
 [8] datasets  methods   base     

other attached packages:
 [1] np_0.60-2          boot_1.3-13        doParallel_1.0.8   iterators_1.0.7   
 [5] foreach_1.4.2      scales_0.2.4       plyr_1.8.2         VineCopula_1.4    
 [9] rugarch_1.3-4      copula_0.999-13    caschrono_1.4      timeSeries_3012.99
[13] its_1.1.8          Hmisc_3.15-0       ggplot2_1.0.1      Formula_1.2-1     
[17] survival_2.37-7    lattice_0.20-29    forecast_5.9       timeDate_3012.100 
[21] zoo_1.7-12         urca_1.2-8         tseries_0.10-34   

loaded via a namespace (and not attached):
 [1] acepack_1.3-3.3             ADGofTest_0.3              
 [3] cluster_1.15.3              codetools_0.2-9            
 [5] colorspace_1.2-6            cubature_1.1-2             
 [7] digest_0.6.8                DistributionUtils_0.5-1    
 [9] expm_0.99-1.1               foreign_0.8-61             
[11] fracdiff_1.4-2              GeneralizedHyperbolic_0.8-1
[13] gsl_1.9-10                  gtable_0.1.2               
[15] igraph_0.7.1                KernSmooth_2.23-13         
[17] ks_1.9.4                    latticeExtra_0.6-26        
[19] MASS_7.3-35                 Matrix_1.1-4               
[21] misc3d_0.8-4                munsell_0.4.2              
[23] mvtnorm_1.0-2               nloptr_1.0.4               
[25] nnet_7.3-8                  numDeriv_2012.9-1          
[27] proto_0.3-10                pspline_1.0-16             
[29] quadprog_1.5-5              RColorBrewer_1.1-2         
[31] Rcpp_0.11.5                 reshape2_1.4.1             
[33] rgl_0.95.1201               rpart_4.1-8                
[35] Rsolnp_1.15                 SkewHyperbolic_0.3-2       
[37] spd_2.0-0                   stabledist_0.6-6           
[39] stats4_3.1.2                stringr_0.6.2              
[41] tools_3.1.2                 truncnorm_1.0-7            
[43] xts_0.9-7                  

但是，任务管理器显示只使用了4个核心（请参阅下面的快照）。你对此有解释吗？感谢。

编辑：例如，我使用以下代码

{{1}}

编辑2：SessionInfo给出

{{1}}