HDL Coder Java null pointer exception during automatic Fixed-Point conversion

I was testing a design with HDL Coder and kept running into a Java NullPointerException. To debug the issue, I created several simple tests each involving matrix-wise power, matrix transpose, and complex numbers, HDL Coder still reports basically same errors for these operations.

Error code:

Exception in thread "AWT-EventQueue-0": java.lang.NullPointerException

at com.mathworks.toolbox.coder.model.MetadataTree.getFunctionNode(MetadataTree.java:59)

at com.mathworks.toolbox.coder.model.MetadataTree.getNode(MetadataTree.java:44)

at com.mathworks.toolbox.coder.model.MetadataTree.put(MetadataTree.java:27)

at com.mathworks.toolbox.coder.mi.ConversionUtils.convertRangesAndTypes(ConversionUtils.java:562)

at com.mathworks.toolbox.coder.mi.ConversionUtils.convertRangesAndTypes(ConversionUtils.java:500)

at com.mathworks.toolbox.coder.fixedpoint.FixedPointController.handleSimulationResults(FixedPointController.java:690)

at com.mathworks.toolbox.coder.fixedpoint.FixedPointController.access$1100(FixedPointController.java:71)

at com.mathworks.toolbox.coder.fixedpoint.FixedPointController$11.handleResult(FixedPointController.java:506)

at com.mathworks.toolbox.coder.mi.FevalCommand$1.run(FevalCommand.java:119)

at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)

at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)

at java.awt.EventQueue.access$500(EventQueue.java:97)

at java.awt.EventQueue$3.run(EventQueue.java:709)

at java.awt.EventQueue$3.run(EventQueue.java:703)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)

at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)

at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Answer 1

[Marie Anna Noviello]

1.Rewrite matrix operations explicitly

Instead of:

Y = (A.^2).';

Do:

for i = 1:N
    Y(i) = real(A(i))*real(A(i)) - imag(A(i))*imag(A(i));
end

(or separate real/imag vectors explicitly)

2. Avoid complex numbers internally

HDL Coder works much better if you represent complex signals as:

A_re, A_im

and handle arithmetic manually.

3. Disable fixed-point conversion to confirm

To verify the root cause:

hdlcfg = coder.config('hdl');
hdlcfg.GenerateHDLCode = true;

If the error disappears, it confirms the crash is in fixed-point / range analysis, not your algorithm.

4. Use coder.extrinsic (last resort)

If the operation is only for simulation / testbench:

coder.extrinsic('power')

This excludes it from HDL generation.

Answer 2

[Navan Ruthramoorthy]

Hi Xiaotong,

Your test bench files do not seem to be calling the design files you have attached. For example, the function tb_hdl_matrix_power calls hdl_matrix_power which is not attached. But you have attached hdl_array_power.m.

Could you share which release you are using?

To see a working example you can type

>> mlhdlc_demo_setup sfir

This will create a temporary folder with sample design and testbench. You can use the files mlhdlc_sfir (design) and mlhdlc_sfir_tb (test bench) from the temporary directory that got created and try HDL code generation.