explicitly cast shmem_map_size #633

Job	Run time
Compute matrix	6s
Doxygen check	16s
Verify Dev Containers / Verify devcontainers	11s
CUDA12.4 gcc / amd64 / Build gcc12/C++17 / Build gcc12/C++17	3m 30s
CUDA11.8 gcc / amd64 / Build gcc11/C++17 / Build gcc11/C++17	3m 3s
CUDA12.4 gcc / arm64 / Build gcc12/C++17 / Build gcc12/C++17	3m 32s
Verify Dev Containers / List devcontainers	4s
Verify Dev Containers / cuda12.4-gcc12	1m 9s
Verify Dev Containers / cuda11.8-gcc11	2m 22s
Verify Dev Containers / cuda12.4-gcc12	1m 16s
CUDA11.8 gcc / amd64 / Test gcc11/C++17 / Test gcc11/C++17	5m 23s
CUDA12.4 gcc / arm64 / Test ${{ inputs.test_name }}	0s
CUDA12.4 gcc / amd64 / Test gcc12/C++17 / Test gcc12/C++17	5m 45s
CI success	1s
	26m 38s

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