The computed word length of the result is 152 bits.

Hello there,

I'm converting Matlab Code (.m) to VHDL Code.. I got the following error

Can you please help me to control the Word Length of the variable??

Error:
The computed word length of the result is 152 bits. This exceeds the maximum supported wordlength of 128 bits.

The Array variable:

0
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-0.498000000000000
-0.0360000000000000
-0.516000000000000
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-0.540000000000000
-0.0840000000000000
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-0.108000000000000
-0.594000000000000
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-0.174000000000000
-0.666000000000000
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-0.264000000000000
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-0.324000000000000
-0.822000000000000
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-0.462000000000000
-0.0360000000000000
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-0.606000000000000
-0.216000000000000
-0.762000000000000
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-0.930000000000000
-0.552000000000000
-0.180000000000000
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-0.762000000000000
-0.432000000000000
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-0.414000000000000
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-0.0420000000000000
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0
0
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-0.0720000000000000
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-0.198000000000000
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-0.318000000000000
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-0.462000000000000
-0.546000000000000
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-0.870000000000000
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-0.546000000000000
-0.0360000000000000
-0.462000000000000
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-0.390000000000000
-0.822000000000000
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-0.174000000000000
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-0.138000000000000
-0.594000000000000
-0.108000000000000
-0.564000000000000
-0.0840000000000000
-0.540000000000000
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-0.420000000000000
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-0.528000000000000
-0.210000000000000
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-0.504000000000000
-0.180000000000000
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-0.444000000000000
-0.102000000000000
-0.690000000000000
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-0.918000000000000
-0.558000000000000
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-0.756000000000000
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-0.00600000000000000
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-0.870000000000000
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-0.0660000000000000
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-0.810000000000000
-0.390000000000000
-0.900000000000000
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-0.0420000000000000
-0.546000000000000
-0.114000000000000
-0.612000000000000
-0.174000000000000
-0.672000000000000
-0.228000000000000
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-0.420000000000000
-0.900000000000000
-0.444000000000000
-0.918000000000000
-0.462000000000000

[Walter Roberson]

I suspect it is not talking about the array itself, but about some value computed using the array.

Answer 1

[Tim McBrayer]

Some operation that you are performing on this data is growing the numeric result to 152 bits, and HDL Coder has a maximum bit length of a word of 128 bits. Keep in mind that HDL Coder attempts to use full precision arithmetic for any temporaries implied by your code. For example, if you are multiply 8, 19-bit fixpt values together without using explicit temporaries, you get a 152-bit result. Of course there are any number of ways to get a 152-bit result; this is just an example.

 >> a = fi(2, 1, 19, 0)
 a = 
     2

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 19
        FractionLength: 0
 >> a*a*a*a*a*a*a*a
 ans = 
   256

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 152
        FractionLength: 0
 >>