---
title: thunder.executors.passes.del_last_used
canonical: >-
  https://lightning.ai/docs/thunder/stable/api-reference/generated/thunder.executors.passes.del_last_used
---
# thunder.executors.passes.del_last_used {#thunder-executors-passes-del-last-used}

### `thunder.executors.passes.del_last_used(trace, *, clear_mutable_collections=False)` {#thunder.executors.passes.del_last_used}

[\[source\]](https://github.com/Lightning-AI/lightning-thunder/blob/0.2.6/thunder/executors/passes.py#L261-L288)

Mark last used intermediates to be deleted. This lets the Python garbage collector free

unused tensor memory.

Parameters:

*   **trace** ([`TraceCtx`](/docs/thunder/core/generated/thunder.core.trace.TraceCtx#thunder.core.trace.TraceCtx "thunder.core.trace.TraceCtx")) – trace to be transformed
    
*   **clear\_mutable\_collections** – whether to clear collections
    
*   **trace** ([_TraceCtx_](/docs/thunder/core/generated/thunder.core.trace.TraceCtx#thunder.core.trace.TraceCtx "thunder.core.trace.TraceCtx")) –
    

Returns:

transformed trace

Return type:

[list](https://docs.python.org/3/builtins/stdtypes.html#list "(in Python v3.15)")

---

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