> ## Documentation Index
> Fetch the complete documentation index at: https://sdk.cerebras.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# CSL Compiler

> Use `cslc` to compile CSL programs with options for output, parameters, colors, target architecture, fabric dimensions, memcpy support, and more.

The CSL compiler is invoked with the command `cslc` on your terminal. See
[Working With Code Samples](/csl/working-with-code-samples) for usage
examples.

## Synopsis

```text theme={"languages":{"custom":["/languages/csl-tmlanguage.json"]}}
cslc <csl_filename> [-o OUTPUT_NAME] [--arch=ARCH]
     [--fabric-dims=W,H] [--fabric-offsets=X,Y]
     [--params NAME:VALUE[,...]] [--colors NAME:VALUE[,...]]
     [--memcpy] [--channels N]
     [--fp16-format=FORMAT]
     [--import-path DIR]
     [--width-west-buf N] [--width-east-buf N]
     [--output-json[=PATH]] [--out-routes]
     [--max-inlined-iterations N] [--comptime-func-depth-limit N]
     [--max-parallelism N] [-g0]
     [--warnings-as-errors] [--verbose] [-h]
```

`<csl_filename>` is the top-level CSL source file (typically `layout.csl`).

## Output

### `-o OUTPUT_NAME`

Output directory name. ELF files and other build artifacts are written under
this directory. Default: `out`.

### `--output-json[=PATH]`

Write a JSON file containing the resolved compilation parameters. If `PATH`
is omitted, the file is named based on `-o` with a `.json` extension. This is
the file host code typically reads to recover `--params` values at run time.

### `--out-routes`

Print an ASCII table of per-PE color and routing information during
compilation. Useful for debugging routes.

## Target architecture and fabric

### `--arch=ARCH`

Select the target architecture. Valid values: `wse2`, `wse3`. Default: `wse2`.
The architecture you compile for must match the system you intend to run on.

### `--fabric-dims=W,H`

Width and height of the target fabric in PE units. For simulator runs, any
bounding box large enough to contain your program rectangle suffices; for
hardware, these must match the actual fabric dimensions of your CS system.

### `--fabric-offsets=X,Y`

Offset of the upper-left corner of your program rectangle within the fabric.
Together with `--fabric-dims`, this defines where the program lives on the
fabric.

### `--fp16-format=FORMAT`

Choose which 16-bit floating-point format may be used at runtime. Valid
values:

* `f16` — IEEE half precision (5-bit exponent, 10-bit mantissa). The default.
* `cb16` — Cerebras float16 (6-bit exponent, 9-bit mantissa, customized bias).
* `bf16` — Brain float16 (8-bit exponent, 7-bit mantissa).

Values of the other two FP16 types must be comptime-known. See
[FP16 Types](/csl/language/types#fp16-types).

## Compile-time parameters and colors

### `--params NAME:VALUE[,...]`

Set the values of CSL source `param` declarations. The argument is a
comma-separated list of `name:value` pairs where `name` matches a `param`
in the source and `value` is an unsigned integer. May be specified multiple
times; all values are concatenated.

### `--colors NAME:VALUE[,...]`

Set the values of CSL source color declarations. Same format as `--params`.
May be specified multiple times.

## Memcpy

### `--memcpy`

Add memcpy infrastructure to the program, enabling host-device data transfer
and host-side function launches via [`SdkRuntime`](/api-docs/sdkruntime-api).
Almost all SDK programs use this.

### `--channels N`

Number of memcpy I/O channels. Required when `--memcpy` is used; the value
must be at least 1 and no larger than the height of the program rectangle
(maximum 16). Higher values increase host-device throughput; performance
improvements are typically minimal past 8.

## Module imports

### `--import-path DIR`

Add `DIR` to the list of directories searched for `<...>` paths in
`@import_module` and `@set_tile_code` statements. May be specified multiple
times; directories are searched in command-line order, before the compiler's
built-in library directory.

## Fabric I/O buffering

### `--width-west-buf N`

Width of the west buffer. Default: `0` (no buffer). Increase to mitigate slow
input from the west edge of the fabric.

### `--width-east-buf N`

Width of the east buffer. Default: `0` (no buffer). Increase to mitigate slow
output to the east edge of the fabric.

## Compile-time limits

### `--max-inlined-iterations N`

Maximum number of iterations allowed when the compiler unrolls inline loops.
If exceeded, compilation fails. Default: `0`, interpreted as no limit. Set
this if a comptime loop is expanding more than you expect.

### `--comptime-func-depth-limit N`

Maximum depth of the comptime function-call stack. If exceeded, compilation
fails. Default: `0`, interpreted as no limit. Set this if a recursive
comptime function is exploring an unbounded space.

### `--max-parallelism N`

Limit the compiler's internal parallelism to `N` workers. Default: `0`,
interpreted as no limit. Lower this on shared build machines.

## Debug and diagnostics

### `-g0`

Disable DWARF debug-information generation. Without this option, the
compiler always emits debug info in ELF files.

### `--warnings-as-errors`

Treat all compiler warnings as errors.

### `--verbose`

Verbose output. Prints information about each compiler phase and additional
diagnostics if linking fails.

### `-h`, `--help`

Print usage information and exit.