# How to force float32?

**URL:** <https://discourse.pymc.io/t/how-to-force-float32/12947>\
**Category:** v5\
**Created:** [September 20, 2023, 2:12pm UTC](https://discourse.pymc.io/t/how-to-force-float32/12947 "2023-09-20T14:12:05Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ron\_Budnar](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/ron_budnar/32/7191_2.png) [@Ron\_Budnar](https://discourse.pymc.io/u/Ron_Budnar)\
**Post date:** [September 20, 2023, 2:12pm UTC](https://discourse.pymc.io/t/how-to-force-float32/12947/1 "2023-09-20T14:12:05Z")

</div>

Hi,

I’ve got some slow running models (on GPU, using numpyro sampler) and I’ve seen that using float32 should in theory be faster than float64. Similar to [this post](https://discourse.pymc.io/t/float32-not-working-with-pytensor-worked-with-aesara/12089), I’m trying to force the use of float32, but it doesn’t appear to be working. As a very simplified repro, the following snippet raises `Exception: You are creating a TensorVariable with float64 dtype. You requested an action via the PyTensor flag warn_float64={ignore,warn,raise,pdb}.`:

```auto
import pymc as pm
import pytensor as pt

pt.config.floatX = "float32"
pt.config.warn_float64 = "raise"

with pm.Model() as model:
    sigma = pm.HalfNormal("sigma", 1.0)
    z_beta = pm.Normal(z_beta", =0.0,=1.0)
    az_data = pm.sample(1000, tune=500)

```

Exception:

> ****
>
> ```auto
> ERROR (pytensor.graph.rewriting.basic): Traceback (most recent call last):
> File ".venv/lib/python3.10/site-packages/pytensor/graph/rewriting/basic.py", line 1922, in process_node
> replacements = node_rewriter.transform(fgraph, node)
> File ".venv/lib/python3.10/site-packages/pytensor/graph/rewriting/basic.py", line 1082, in transform
> return self.fn(fgraph, node)
> File ".venv/lib/python3.10/site-packages/pytensor/tensor/rewriting/basic.py", line 989, in local_sum_make_vector
> add(*[cast(value, acc_dtype) for value in elements]), out_dtype
> File ".venv/lib/python3.10/site-packages/pytensor/tensor/rewriting/basic.py", line 989, in <listcomp>
> add(*[cast(value, acc_dtype) for value in elements]), out_dtype
> File ".venv/lib/python3.10/site-packages/pytensor/tensor/basic.py", line 755, in cast
> return _cast_mapping[dtype_name](x)
> File ".venv/lib/python3.10/site-packages/pytensor/graph/op.py", line 304, in __call__
> node = self.make_node(*inputs, **kwargs)
> File ".venv/lib/python3.10/site-packages/pytensor/tensor/elemwise.py", line 497, in make_node
> outputs = [
> File ".venv/lib/python3.10/site-packages/pytensor/tensor/elemwise.py", line 498, in <listcomp>
> TensorType(dtype=dtype, shape=shape)()
> File ".venv/lib/python3.10/site-packages/pytensor/graph/type.py", line 228, in __call__
> return utils.add_tag_trace(self.make_variable(name))
> File ".venv/lib/python3.10/site-packages/pytensor/graph/type.py", line 200, in make_variable
> return self.variable_type(self, None, name=name)
> File ".venv/lib/python3.10/site-packages/pytensor/tensor/var.py", line 860, in __init__
> raise Exception(msg)
> Exception: You are creating a TensorVariable with float64 dtype. You requested an action via the PyTensor flag warn_float64={ignore,warn,raise,pdb}.
> 
> ```

Note that if I comment either `sigma = ...` or `z_beta = ...` no exceptions are raised.

This is on pymc v5.6.1. I feel like I’m missing something simple, so any help would be appreciated.