# My accelerator DMA output is giving zeros

**URL:** <https://discuss.pynq.io/t/my-accelerator-dma-output-is-giving-zeros/3202>\
**Category:** Support\
**Created:** [October 27, 2021, 3:13pm UTC](https://discuss.pynq.io/t/my-accelerator-dma-output-is-giving-zeros/3202 "2021-10-27T15:13:28Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![anoir\_nechi](https://avatars.discourse-cdn.com/v4/letter/a/bbe5ce/32.png) [@anoir\_nechi](https://discuss.pynq.io/u/anoir_nechi)\
**Post date:** [October 27, 2021, 3:13pm UTC](https://discuss.pynq.io/t/my-accelerator-dma-output-is-giving-zeros/3202/1 "2021-10-27T15:13:28Z")

</div>

I have created the following IP with Vitis HLS 2020.2 (Please check the attached files [pobj.cpp](https://discuss.pynq.io/uploads/short-url/8TPx04g8uQsElNdeTy5nFf1Q2Ca.cpp) (2.5 KB) [pobj.hpp](https://discuss.pynq.io/uploads/short-url/juShJxsQWLKQa0O7EEWLIqwhj0N.hpp) (327 Bytes)) and successfully synthesized and generated an IP. After that I created the following block design:

 ![Screenshot from 2021-10-27 17-07-23](https://us1.discourse-cdn.com/flex019/uploads/pynq1/original/2X/7/7226adde89a3966bdfe8b67d1037183edaa63067.png)  
and generated the bitstream also successfully  
Then I started the python coding step as follows:

```auto
from pynq import (allocate, Overlay)
import numpy as np
ol = Overlay('pobj.bit')

# Define dimensions
M = 64
N = 512
# Allocate memory for DMA transfers
A_buffer = allocate(shape=(M,N), dtype=np.float64, cacheable=False)
X_buffer = allocate(shape=(N,1), dtype=np.float64, cacheable=False)
Y_buffer = allocate(shape=(M,1), dtype=np.float64, cacheable=False)
Z_buffer = allocate(shape=(M,1), dtype=np.float64, cacheable=False)
P_buffer = allocate(shape=(2,1), dtype=np.float64, cacheable=False)

CTRL_REG = 0x00
AP_START = (1<<0) # bit 0
AUTO_RESTART = (1<<7) # bit 7
def run_kernel():
    dma_A.sendchannel.transfer(A_buffer)
    dma_X.sendchannel.transfer(X_buffer)
    dma_YZ.sendchannel.transfer(Y_buffer)
    dma_param.sendchannel.transfer(P_buffer)
    
    dma_YZ.recvchannel.transfer(Z_buffer)
    dma_param.recvchannel.transfer(P_buffer)
    
    pobj_ip.write(CTRL_REG, (AP_START | AUTO_RESTART)) # initialize the module
    
    dma_A.sendchannel.wait()
    dma_X.sendchannel.wait()
    dma_YZ.sendchannel.wait()
    dma_param.sendchannel.wait()
    
    dma_YZ.recvchannel.wait()
    dma_param.recvchannel.wait()

A = np.random.rand(M, N).astype(dtype=np.float64)
X = np.random.rand(N,1).astype(dtype=np.float64)
Y = np.random.rand(M,1).astype(dtype=np.float64)
P = np.zeros((2,1)).astype(dtype=np.float64)
P[0] = 0.5 #lambda

A_buffer[:] = A
X_buffer[:] = X
Y_buffer[:] = Y
P_buffer[:] = P

%%timeit
run_kernel()
# 100 loops, best of 3: 17.1 ms per loop
print(Z_buffer)
# all zeros

```

First of all the IP is so slow and more importantly, its output is zeros … What’s wrong?  
How could I solve these issues?

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<div class="post-metadata">

**Author:** ![Roua\_Zaied](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/roua_zaied/32/2863_2.png) [@Roua\_Zaied](https://discuss.pynq.io/u/Roua_Zaied)\
**Post date:** [June 6, 2022, 8:36am UTC](https://discuss.pynq.io/t/my-accelerator-dma-output-is-giving-zeros/3202/2 "2022-06-06T08:36:35Z")

</div>

i try to run your code but i hve missing string.h file  
INFO: [HLS 200-10] Analyzing design file ‘roua/pobj.cpp’ …  
ERROR: [HLS 207-812] ‘string.h’ file not found: roua/pobj.cpp:2:10  
INFO: [HLS 200-111] Finished Command csynth\_design CPU user time: 0.76 seconds. CPU system time: 0.55 seconds. Elapsed time: 0.9 seconds; current allocated memory: 197.892 MB.  
command ‘ap\_source’ returned error code  
while executing  
“source /home/roua/Desktop/roua/solution1/csynth.tcl”  
invoked from within  
“hls::main /home/roua/Desktop/roua/solution1/csynth.tcl”