Glyd for Python

Lossless AI compression: 33% less GPU memory, bit for bit.

curl -LsSf https://getglyd.com/install.sh | sh   # a model on your GPU in two commands: Linux, an NVIDIA GPU, driver 580 or newer
glyd run Qwen/Qwen3.5-9B                         # downloads it, starts it packed, and chats (glyd serve, glyd doctor)
glyd run Qwen/Qwen3.8-27B:swift                  # fewer bits, not lossless: :kestrel 6.5 bits per weight, :swift 5.5

pip install "glyd[gpu]"   # models on the GPU: Linux x86_64 / aarch64, an NVIDIA GPU (Ampere or later)
pip install "glyd[vllm]"  # and serving them: vllm serve MODEL --quantization glyd (vLLM 0.30)
pip install glyd          # the codec alone: Linux x86_64 / aarch64, macOS arm64

import glyd
model = glyd.from_pretrained("Qwen/Qwen3.5-9B")               # packed on the GPU as it loads
model = glyd.from_pretrained("Qwen/Qwen3.5-9B", exact=True)   # logits exactly bf16's

Every option: on the GPU below, and getglyd.com for which models fit which GPU.

The codec

Wheels for Linux x86_64 and aarch64 and macOS arm64. From a checkout: bindings/python/build.sh && pip install bindings/python.

import glyd
c = glyd.compress(data)                       # --max; level="ultra" / "cold" / "default"
c = glyd.compress(log_bytes, records=True)    # logs, dumps, CSV, JSON lines as typed columns
data = glyd.decompress(c)

p = glyd.pack(events)                         # many small objects as one stream
event = glyd.unpack(p, 7)

with glyd.Store("bucket/") as s:              # objects compressed across each other
    i = s.put("wed.tar", data)                # a delta against the object it most resembles
    data = s.get(i)
with glyd.Store("meta/", s3="s3://bucket/prefix") as s:   # objects in S3
    ...

A thin ctypes layer over include/glyd.h; no build step beyond placing the shared library. build.sh places libglyd_store, which carries the codec and the store; with libglyd alone (the codec crate) everything but Store works.

On the GPU: a model's weights held compressed

Needs a CUDA GPU (Ampere or later) and pip install "glyd[gpu]" (PyTorch 2.5+ built for CUDA 12 or 13, transformers 5.17+, accelerate, safetensors, huggingface_hub). The glyd-gpu Linux wheels it brings (x86_64, aarch64; glibc 2.28 or later) carry the kernels, libglyd_gpu_cuda12.so and libglyd_gpu_cuda13.so (CUDA 12.8 and 13.0, their runtime linked in), and the one for PyTorch's CUDA is taken; GLYD_GPU_LIB names another. fit needs none of it. The libraries are a C library too, with their header, glyd_gpu.h (8 functions), in the wheel's glyd_gpu directory, for engines in C, C++, Rust or any language with a C FFI.

import glyd
from transformers import AutoTokenizer
model = glyd.from_pretrained("Qwen/Qwen3.5-9B")            # any bf16 checkpoint, packed as it loads, on the GPU
tok = AutoTokenizer.from_pretrained("Qwen/Qwen3.5-9B")
out = model.generate(**tok("Hello", return_tensors="pt").to(model.device), max_new_tokens=64)

model = glyd.from_pretrained("Qwen/Qwen3.5-9B", exact=True) # logits exactly bf16's
glyd.save_pretrained(model, "qwen3.5-9b-glyd")               # the packed format, loads without repacking
model = glyd.from_pretrained("qwen3.5-9b-glyd", verify=True) # re-hashes every weight against the source
print(glyd.fit("Qwen/Qwen3.5-27B", gpu="48GB"))              # will it fit, bf16 against Glyd

glyd.from_pretrained(name_or_path, *, device="cuda:0", layout="auto", exact=False, merge=True, verify=False, compile=True, **hf_kwargs) returns the transformers model (a causal LM, else an image-text-to-text one), ready for generate(). transformers loads it a tensor at a time and every Linear's weight is packed on the GPU as it arrives: the GPU holds the packed model and the largest weight not packed yet, the host about a shard.

• device: the GPU. device_map="auto" (with accelerate) or a device map in hf_kwargs spreads the layers over several.
• layout: "auto" picks for the GPU (mma on Ada, for a mixture of experts on an A10 too, and wherever only it fits; mma12 on A10, A100 and H100); "mma", the most memory off (10.8 bits per weight); "mma12", 12.0 bits a weight, the faster one on an A10, A100 and H100. Embeddings are held compressed too, their rows rebuilt as they are looked up.
• exact: the logits are exactly bf16's (every product multiplies as nn.Linear does). By default the products run straight from the packed weights: faster, their sums in another order than bf16's, so late tokens may differ from bf16's as between any two GEMM kernels.
• merge: q, k, v and gate, up as one product each, as serving engines run them (not with exact).
• verify: every pack unpacked and compared with its weights as it is made; from a saved checkpoint, every packed tensor unpacked and checked against the sha256 in glyd.json, and every other tensor against its own (a save of glyd 0.25 on).
• compile: generate() compiled (below); False, or GLYD_COMPILE=0 in the environment, runs it eager, as transformers runs it.
• hf_kwargs: transformers' from_pretrained's (revision, token, device_map, attn_implementation ...); the dtype is bf16.

glyd.gpu.compress(model, *, layout="auto", exact=False, merge=True, compile=True) packs a model already loaded in bf16 in place, on the GPU its weights are on (the current one for weights on the CPU), and returns it (glyd.compress is the codec's, for bytes).

A mixture of experts is packed too: every mixture-of-experts family of transformers 5.17; with exact=True the experts' products are bf16's own. A saved model holds them packed, and a model with them can't be copied or pickled (copy.deepcopy, torch.save): load it again.

On PyTorch 2.13.0 or later (measured on 2.14), generate() is compiled; below it, a 2.13 pre-release included, it runs eager, as in glyd 0.23. A compiled call runs as generate(..., cache_implementation="static") asks transformers to run it, a static cache and the forward compiled (torch.compile, mode="reduce-overhead": CUDA graphs), so a step's host time goes and what is left is its GPU time. The prompt runs eager (transformers compiles the steps after it).

Greedy tokens compiled can differ from 0.23's eager loop's, as a compiled bf16 model's can from its eager ones. In the default mode they can also vary within a process, between calls whose cache sizes compile differently; exact=True is never compiled and stays exactly bf16's. The first call compiles and captures (faster in a later process, from PyTorch's compile caches); a call whose cache is longer than any before it compiles again once, then captures a graph. Before serving, warm up with one short generate(): the first compiled step comes after the first token is streamed, so a streamer's consumer waits through the compile (give a TextIteratorStreamer a timeout longer than it, or use compile=False). Only greedy and sampled calls compile: a call runs as transformers runs it if it uses several beams, an assistant or another assisted mode (prompt lookup, early exit, use_mtp), its own cache or a cache_implementation, use_cache=False, return_dict_in_generate, attentions or hidden states, custom_generate, or disable_compile=True (one call eager); so does one whose static cache would hold more positions in all (its sequences times the prompt and max_new_tokens, or max_cache_len where longer) than 1280 on a GeForce card and 2048 on another: past that the eager loop is as fast, sooner the faster the host's CPU.

GLYD_COMPILE_MAX sets the cap on any GPU. Not with exact=True (below), a family transformers does not compile whole (its _can_compile_fullgraph), the model over several GPUs, or a transformers whose generation helpers are not as 5.17 has them (one warning at the load), which run eager, nor where transformers 5.17's static cache fails (bf16's too), which run eager from the start: a family none of whose forwards transformers compiles, and a model with multi-head latent attention whose config has fewer key/value heads than heads (released checkpoints, with as many as heads, compile). A call whose forward fails to compile anyway (torch._dynamo's or Inductor's error) runs again eager, from its start (a streamer gets only what the failed attempt had not streamed, and a sampled call draws again from the random state it started with: its tokens and text are the eager run's), and so do the model's later calls, with one warning; any other error (out of memory included) is the call's own, and the next call compiles as before. Several models in one process all compile; the process's own torch._dynamo settings are left as they are. A model that has generated compiled is freed at del, as an eager one.

A bf16 model, or one loaded with compile=False, runs transformers' own generate(). compile=False, or GLYD_COMPILE=0 before the load, takes nothing over. transformers sets TOKENIZERS_PARALLELISM=0 for the process where it compiles; Glyd puts back the value it had, or its absence, after each compiled call (two calls at once in two threads can leave it 0, as transformers' own compiled calls do).

torch.compile(model.forward, mode="reduce-overhead", fullgraph=True) compiles the forward as it would the bf16 model's, likewise. Eager, a step's product has less host time than nn.Linear's. Compile the whole forward, as these do: compiling each layer on its own compiles every layer anew. With exact=True each product in the graph is F.linear's, as eager, but the logits are the bf16 model's compiled the same way bit for bit only with torch._inductor.config.emulate_precision_casts = True (so an exact model's generate() stays eager: its tokens are bf16's eager ones).

glyd.save_pretrained(model, path) writes glyd-v4 (from glyd 0.28): the packed weights as safetensors, the rest of the model as it is, glyd.json (the format, the source repo and revision, and for every packed tensor its shape and the sha256 of its bf16 bytes; from glyd 0.25 the sha256 of every tensor saved as it is), and the source's config, generation config and tokenizer files. Glyd 0.27 and before wrote glyd-v1, and glyd-v2 with a mixture of experts' packs; glyd 0.28 loads both and packs them again as they load, and glyd 0.27 and before refuse a glyd-v4 save by its format. from_pretrained(path) loads the packs as saved; on a GPU where mma12 is the pick, it decodes and packs them again. save_pretrained(model, path, layout="mma12") (pack --layout mma12) saves the mma12 layout instead, as an A10, A100 or H100 runs it (glyd-v3, which glyd 0.24 and before refuse): loaded there as saved, without packing again.

glyd.fit(name_or_path, gpu="48GB", context=8192): whether the model fits one GPU in bf16 and with Glyd, by the site's rule: the weights (with Glyd, bf16 tensors at the ratio measured for the model, else 0.673 of their bytes; FP8 and 4-bit as they are), a KV cache for context tokens and 1.5 GiB for the runtime, against the memory nvidia-smi reports (16GB ... 141GB, or a number of bytes). From the Hub's metadata for a repo id, from the files for a directory.

python -m glyd_gpu fit Qwen/Qwen3.5-27B --gpu 48GB
python -m glyd_gpu pack Qwen/Qwen3.5-9B qwen3.5-9b-glyd     # packed, checked, saved as glyd-v4
python -m glyd_gpu verify qwen3.5-9b-glyd

glyd pack and glyd verify are the same two commands (the glyd program passes them to the Python tool).

Serving with vLLM

glyd run MODEL and glyd serve MODEL (installed by the script above, or by pip install "glyd[vllm]" in a virtual environment) start vLLM with the plugin and the settings worked out from the GPU: memory share, context, the tool-call and reasoning parsers, compiled wherever the chat keeps 8,192 tokens of context (eager only where that gives a longer chat); glyd doctor checks the machine. The docs have the steps. By hand, pip install "glyd[vllm]" installs vLLM 0.30 and the plugin, which vLLM finds by itself (the package's vllm.general_plugins entry point):

vllm serve Qwen/Qwen3.5-9B --quantization glyd       # a bf16 checkpoint, packed as it loads
vllm serve ./SAVE --quantization glyd                # a glyd save, as saved (not yet of a 2026 model)
vllm serve Qwen/Qwen3.5-9B --quantization glyd --enforce-eager --additional-config '{"glyd": {"exact": true}}'

vLLM's own settings need not fit the card: Qwen3.5-9B in bf16 ran out of memory at start on an RTX 4090 (24 GB), even with the context capped at 4,096 tokens, and Glyd's settings run it there packed with a 189,440-token context (log). glyd run works both out from the card, and the docs have the flags by hand.

layout, exact and verify are from_pretrained's options, given in --additional-config's "glyd" (or GLYD_LAYOUT, GLYD_EXACT, GLYD_VERIFY). fraction (0 to 1, GLYD_FRACTION) packs only that share of the decoder layers, spread evenly over the depth, and leaves the rest as vLLM runs them: 0 is bf16, 1 (the default) every layer, and from v0.28 the embedding and the output layer too (every embedding row comes back bit for bit; exact keeps the output layer as vLLM runs it). vLLM sizes its KV cache after the weights load, so the memory the packs save becomes KV cache: Qwen3.8-27B on an H100, 204,117 tokens against bf16's 122,538 at the same --gpu-memory-utilization (benchmarks/gpu/h100-qwen38-v028-2026-10-03). With exact the logits are exactly vLLM's bf16 ones, eager, or compiled in inductor's deterministic mode where the packed Linears have no biases. kv (auto, the default, lossless or off; GLYD_KV) holds vLLM's KV cache in fewer bits, every value read back exactly, for models with head size 128 and full attention only: none of the 2026 models measured so far (Qwen3.5, Qwen3.8, Gemma 4) is one, so they keep vLLM's cache, with a line in the log. auto holds it on an A100, an L4, an H100 and a GH200 and leaves vLLM's own cache on any other GPU, with a line in the log; glyd run keeps vLLM's cache unless GLYD_KV is set, because the first start sets the cache up for the model. Throughput against bf16, exact mode compiled, mixtures of experts and what is not supported yet: the docs.

The GPU half is the glyd-gpu package (compiled wheels; glyd.gpu re-exports its API).

License

From v0.29.0 all of Glyd is under the Business Source License 1.1 (LICENSE). Free forever for personal and non-commercial use (including education, research and nonprofits) on computers you own or rent for yourself, and for anyone to try, test and develop with. Commercial use needs a license: suryakoritala@getglyd.com. Each version becomes Apache-2.0 four years after its release.

Releases up to v0.28 keep the licenses they shipped with.