test_horiz_interp: Don't over-allocate arrays #939

Job	Run time
build (-DOPENMP=on, -DCMAKE_BUILD_TYPE=Release)	11m 33s
build (-DOPENMP=on, -DCMAKE_BUILD_TYPE=Debug)	3m 30s
build (-DOPENMP=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	12m 21s
build (-DOPENMP=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	4m 2s
build (-DOPENMP=on, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Release)	12m 33s
build (-DOPENMP=on, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Debug)	3m 38s
build (-DOPENMP=on, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	13m 4s
build (-DOPENMP=on, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	4m 2s
build (-DOPENMP=off, -DCMAKE_BUILD_TYPE=Release)	11m 15s
build (-DOPENMP=off, -DCMAKE_BUILD_TYPE=Debug)	3m 25s
build (-DOPENMP=off, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	12m 21s
build (-DOPENMP=off, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	3m 55s
build (-DOPENMP=off, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Release)	12m 2s
build (-DOPENMP=off, -DWITH_YAML=on, -DCMAKE_BUILD_TYPE=Debug)	3m 48s
build (-DOPENMP=off, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Release)	13m 1s
build (-DOPENMP=off, -DWITH_YAML=on, -DUSE_DEPRECATED_IO=on, -DCMAKE_BUILD_TYPE=Debug)	3m 51s
	2h 8m 21s

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