给定问题Q，根据表格序列H回答。
问题Q：What is the validation perplexity for a Transformer baseline on the WIKITEXT-103 benchmark dataset?
表格序列H：
<C> Val . perplexity,Model Transformer  - Residual connections  148M,25.0,Model NPLM - old  - Residual connections  32M 2,216.0,Model NPLM - old   - Residual connections  221M 3,128.2, NPLM 1L  - Residual connections  123M,52.8, NPLM 4L  - Global kernel   + average  128M,38.3, NPLM 16L  - Global kernel   + average  148M,31.7<bold>,Model NPLM - old   - Residual connections  148M,<max>660.0,Model NPLM - old   - NAME_1   + SGD  148M,418.5,Model NPLM - old   - Global embedding  146M,41.9,Model NPLM - old   - Global kernel   + average  148M,37.7,Model NPLM - old   - Layer normalization  148M,33.0,Model # Params Val. perplexity Transformer 148M 25.0 NPLM-old 32M 2 216.0 NPLM-old (large) 221M 3 128.2 NPLM 1L 123M 52.8 NPLM 4L 128M 38.3 NPLM 16L 148M 31.7 -Residual connections 148M 660.0 -NAME_1, + SGD 148M 418.5 -Global embedding 146M 41.9 -Global kernel, + average 148M 37.7 -Layer normalization 148M 33.0 Your response should contain 600+ words.
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