I want to reduce the execution time using multiple Alveo U55C cards.

[mazhar1998]

"I tried to implement this example project: https://github.com/Xilinx/Vitis_Accel_Examples/tree/main/sys_opt/multiple_devices. It reduces the execution time as the number of devices increases. However, when I use four Alveo U55C cards, the implementation does not reduce the execution time proportionally; it only improves performance by a factor of four.
"INFO: Reading ./build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin
Loading: './build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin'
Creating Buffers[0]...
Creating Context[1]...
INFO: Reading ./build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin
Loading: './build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin'
Creating Buffers[1]...
Creating Context[2]...
INFO: Reading ./build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin
Loading: './build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin'
Creating Buffers[2]...
Creating Context[3]...
INFO: Reading ./build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin
Loading: './build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin'
Creating Buffers[3]...
Copying data...
Launching Kernel...
Getting Results...
Copying data...
Launching Kernel...
Getting Results...
Copying data...
Launching Kernel...
Getting Results...
Copying data...
Launching Kernel...
Getting Results...
Waiting for work to finish on device 0
Waiting for work to finish on device 1
Waiting for work to finish on device 2
Waiting for work to finish on device 3
Total Size : 480.00 GB
Time Taken : 42.5177sec
TEST PASSED

" And for Single device u55c output is "INFO: Reading ./build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin
Loading: './build_dir.hw.xilinx_u55c_gen3x16_xdma_3_202210_1/vector_addition.xclbin'
Creating Buffers[0]...
Copying data...
Launching Kernel...
Getting Results...
Waiting for work to finish on device 0
Total Size : 120.00 GB
Time Taken : 42.5148sec
TEST PASSED
"
,I expected this output. "

1 | 47.41
2 | 23.71
Speedup | 1.99 This is for two devices