Running mamba seems to run single threaded on NixOs with AMD CPU

[Corallus-Caninus]

I am running cargo run --release --example mamba -- prompt "Mamba is the" on amd cpu without cuda on a fresh clone of candle. It seems to only use single threading.

Is this expected? I tried setting RAYON_NUM_THREADS but still single threaded. I installed rust toolchain using nixos and ensured I have all the required llvm dependencies, also using nixos packages.

[Corallus-Caninus]

USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
REDACTED 529448 94.8 15.3 12174100 11356460 pts/8 Rl+ 15:51 41:24 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.9 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:43 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.8 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:39 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.7 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:38 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.7 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:37 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.6 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:36 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.6 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:35 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.5 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:33 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.4 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:31 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.4 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:28 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.2 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:25 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 3.1 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:21 target/release/examples/mamba-trainer --prompt blah --which mamba130m
REDACTED 529448 2.9 15.3 12174100 11356460 pts/8 Sl+ 15:51 1:15 target/release/examples/mamba-trainer --prompt blah --which mamba130m