Hi there,

I'm try to use DEXSeq to analysis differential exon usage and it worked fine with small sample sizes. But when my sample size goes over 30, the "estimateExonFoldChanges" function start to output the following error:

"Error in .local(x, ...):
 cannot create 126 workers; 125 connections available in this session"

I tried both parallel version (with different number of workers specified) and serial version and met the same problem.

Does anyone know what's causing this error and how to solve it?

BTW, here's my R session info:
R version 3.3.2 (2016-10-31)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: CentOS release 6.7 (Final)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8     LC_MONETARY=en_US.UTF-8   
 [6] LC_MESSAGES=en_US.UTF-8    LC_PAPER=en_US.UTF-8       LC_NAME=C                  LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats4    parallel  stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] DEXSeq_1.20.2              RColorBrewer_1.1-2         AnnotationDbi_1.36.0       DESeq2_1.14.1              SummarizedExperiment_1.4.0
 [6] GenomicRanges_1.26.1       GenomeInfoDb_1.10.1        IRanges_2.8.1              S4Vectors_0.12.2           Biobase_2.34.0            
[11] BiocGenerics_0.20.0        BiocParallel_1.8.1         ggplot2_2.2.1              dplyr_0.5.0               

loaded via a namespace (and not attached):
 [1] genefilter_1.56.0   statmod_1.4.30      locfit_1.5-9.1      splines_3.3.2       lattice_0.20-34     colorspace_1.3-2    htmltools_0.3.6    
 [8] survival_2.39-5     XML_3.98-1.5        rlang_0.1.1         foreign_0.8-67      DBI_0.5-1           plyr_1.8.4          stringr_1.2.0      
[15] zlibbioc_1.20.0     Biostrings_2.42.1   munsell_0.4.3       gtable_0.2.0        hwriter_1.3.2       memoise_1.0.0       latticeExtra_0.6-28
[22] knitr_1.17          biomaRt_2.30.0      geneplotter_1.52.0  htmlTable_1.7       Rcpp_0.12.11        acepack_1.4.1       xtable_1.8-2       
[29] openssl_0.9.5       scales_0.4.1        base64_2.0          Hmisc_4.0-1         annotate_1.52.0     XVector_0.14.0      Rsamtools_1.26.1   
[36] gridExtra_2.2.1     digest_0.6.12       stringi_1.1.5       grid_3.3.2          tools_3.3.2         bitops_1.0-6        magrittr_1.5       
[43] lazyeval_0.2.0      RCurl_1.95-4.8      tibble_1.3.3        RSQLite_1.1-1       Formula_1.2-1       cluster_2.0.5       Matrix_1.2-7.1     
[50] data.table_1.10.0   assertthat_0.1      R6_2.2.0            rpart_4.1-10        nnet_7.3-12 

Thanks in advance!

Cheers,
Chen 

UPDATE:

I updated R and DEXSeq to the latest version (R 3.4.1, DEXSeq 1.22.0) and still got the same error. Please note that with sample size smaller than 30, the code works perfectly fine.

Here's my code:

dxd <- estimateSizeFactors(dxd)
BPPARAM <- MulticoreParam(workers=detectCores()/2)
formulaFullModel = ~ sample + exon + libType:exon + condition:exon
formulaReducedModel = ~ sample + exon + libType:exon
dxd <- estimateDispersions(dxd, formula=formulaFullModel, BPPARAM=BPPARAM)
dxd_deu <- testForDEU(dxd, reducedModel=formulaReducedModel, fullModel=formulaFullModel, BPPARAM=BPPARAM)
dxd_fc <- estimateExonFoldChanges(dxd_sig)