How to run Velvet in multiple k-mers?

Question

[kanshenglong]

Hello members, I would like to run velvet in multiple k-mers. The velveth run noamally($velveth /work_dict/ 31,35,2 -fastq.gz -shortPaired -separate reads_1.fastq.gz reads_2.fastq.gz), but when run velvetg there still wrong($velvetg /work_dict/ -cov_cutoff 5 -ins_length 250 -ins_length_sd 40 -exp_cov 50-500 -min_contig_lgth 500 -scaffolding yes ).

The following text is log file: [1290.458821] === Sequences loaded in 201.655921 s [1291.105881] Done inputting sequences [1291.105888] Destroying splay table [1293.147335] Splay table destroyed [0.000000] No Roadmap file to build upon! Please run velveth (see manual)

Thanks!!