I don't know why it tells me that I previously used as a variable when I have never used it before.
Here is my code:
price := 0;
temp := 0;
for i=1:m,
price += -y(i)*log( sigmoid(theta'*X(i,:)) ) -(1-y(i))*log(1-sigmoid(theta'*X(i,:)) );
end;
J = price / m;
for i=1:n,
temp := 0;
for i2=1:m,
temp += ( 1-sigmoid(theta'*X(i2,:)) - y(i2) ) * X(j,i2);
end;
grad(i) = temp;
end;
The error is here:
'price += -y(i)*log( sigmoid(theta'*X(i,:)) ) -(1-y(i))*log(1-sigmoid(theta'*X(i,:)) );'
Log error:
"price" was previously used as a variable, conflicting with its use here as the name of a function or command.
See "How MATLAB Recognizes Command Syntax" in the MATLAB documentation for details.
I guess there is nothing like += in Matlab. So, you can't do the following.
price += -y(i)*log(sigmoid(theta'*X(i,:))) - (1-y(i))*log(1-sigmoid(theta'*X(i,:)));
Rather you should do the following.
price = price + -y(i)*log(sigmoid(theta'*X(i,:))) -(1-y(i))*log(1-sigmoid(theta'*X(i,:)));
Moreover, := is not allowed according to Matlab language. Perhaps, your code is in Mupad. Check this out.
Related
I'm designing a module that accepts multiple channels and outputs one channel.
Each channel consists of valid signal and data of some widths.
If a channel has valid data, the module should output that channel. If multiple channels have valid data, the module should output one of them (in my case, channel with highest index) and rests are dropped.
My simple implementation looks like this:
module test1 #(
parameter NUM_CHANNEL = 8,
parameter DATA_WIDTH = 512
) (
input logic [DATA_WIDTH - 1 : 0] data_in [NUM_CHANNEL],
input logic valid_in [NUM_CHANNEL],
output logic [DATA_WIDTH - 1 : 0] data_out,
output logic valid_out
);
always_comb begin
valid_out = 0;
for (int i = 0; i < NUM_CHANNEL; ++i) begin
if (valid_in[i]) begin
valid_out = 1;
data_out = data_in[i];
end
end
end
endmodule
This works perfectly in both simulation and real circuit (FPGA).
However, channel can be complex type so I used interface like this:
interface channel #(
parameter DATA_WIDTH = 512
);
logic valid;
logic [DATA_WIDTH - 1 : 0] data;
modport in (
input valid,
input data
);
modport out (
output valid,
output data
);
endinterface // sub_csr_if
module test #(
parameter NUM_CHANNEL = 8,
parameter DATA_WIDTH = 512
) (
channel.in in[NUM_CHANNEL],
channel.out out
);
always_comb begin
out.valid = 0;
for (int i = 0; i < NUM_CHANNEL; ++i) begin
if (in[i].valid) begin
out.valid = 1;
out.data = in[i].data;
end
end
end
endmodule
Then, this code gets Nonconstant index into instance array 'sub_port'. error in ModelSim, and i is not a constant error in Quartus.
If I unroll the loop, it works but it becomes non-parametric code. (only works for fixed NUM_CHANNEL)
Why the latter one does not work, while the first one works flawlessly?
An array of instances (module or interface) is not a true array type. As your error message indicates, you cannot select a particular instance with a variable index. With a true array, every element is identical. Because of the way parameterization, defparam, and port connections work, each instance element could have differences. The elaboration process essentially flattens all hierarchy before simulation begins.
What you can do is use a generate construct to select your instance as follows
;
module test #(
parameter NUM_CHANNEL = 8,
parameter DATA_WIDTH = 512
) (
channel.in in[NUM_CHANNEL],
channel.out out
);
logic _valid[NUM_CHANNEL];
logic [DATA_WIDTH - 1 : 0] _data[NUM_CHANNEL];
for (genvar ii=0;ii<NUM_CHANNEL;ii++) begin
assign _valid[ii] = in[ii].valid;
assign _data[ii] = in[ii].data;
end
always_comb begin
out.valid = 0;
for (int i = 0; i < NUM_CHANNEL; ++i) begin
if (_valid[i]) begin
out.valid = 1;
out.data = _data[i];
end
end
end
endmodule
i have a question about the pseudo-encrypt function for postgres.
Is there any way that I can reduce the output to 6? I really like this function and want to use it, but only need a output between 1 and 999999.
This question is related to my last question. I want to use it to created unqiue numbers between 1 and 999999.
Thank you.
Use mod on the generated value to generate number in range from start_value to end_value:
select start_value + mod(pseudo_encrypt(number), end_value - start_value + 1);
For your case this will be look like:
select 1 + mod(pseudo_encrypt(23452), 999999);
It's not quite straightforward to set an upper bound of 999999, as the algorithm operates on blocks of bits, so it's hard to get away from powers of two.
You can work around this by cycle walking - just try encrypt(n), encrypt(encrypt(n)), encrypt(encrypt(encrypt(n)))... until you end up with a result in the range [1,999999]. In the interest of keeping the number of iterations to a minimum, you want to adjust the block size to get you as close to this range as possible.
This version will let you specify a range for the input/output:
CREATE OR REPLACE FUNCTION pseudo_encrypt(
value INT8,
min INT8 DEFAULT 0,
max INT8 DEFAULT (2^62::NUMERIC)-1
) RETURNS INT8 AS
$$
DECLARE
rounds CONSTANT INT = 3;
L INT8[];
R INT8[];
i INT;
blocksize INT;
blockmask INT8;
result INT8;
BEGIN
max = max - min;
value = value - min;
IF NOT ((value BETWEEN 0 AND max) AND (max BETWEEN 0 AND 2^62::NUMERIC-1)) THEN
RAISE 'Input out of range';
END IF;
blocksize = ceil(char_length(ltrim(max::BIT(64)::TEXT,'0'))/2.0);
blockmask = (2^blocksize::NUMERIC-1)::INT8;
result = value;
LOOP
L[1] = (result >> blocksize) & blockmask;
R[1] = result & blockmask;
FOR i IN 1..rounds LOOP
L[i+1] = R[i];
R[i+1] = L[i] # ((941083981*R[i] + 768614336404564651) & blockmask);
END LOOP;
result = (L[rounds]::INT8 << blocksize) | R[rounds];
IF result <= max THEN
RETURN result + min;
END IF;
END LOOP;
END;
$$
LANGUAGE plpgsql STRICT IMMUTABLE;
I can't guarantee its correctness, but you can easily show that it maps [1,999999] back to [1,999999]:
SELECT i FROM generate_series(1,999999) s(i)
EXCEPT
SELECT pseudo_encrypt(i,1,999999) FROM generate_series(1,999999) s(i)
i was "finding Pi" with Monte Carlo Method, but the answer was incorrect. The oryginal code was:
RandomTools[MersenneTwister]: with(Statistics):
tries := 10000:
s := 0;
for i to tries do
if GenerateFloat()^2+GenerateFloat()^2 < 1 then s := s+1 end if;
end do:
evalf(4*s/tries)
It gives answer aroud 2.8-2.85
when I change the code to
s := 0;
x := Array([seq(GenerateFloat(), i = 1 .. tries)]);
y := Array([seq(GenerateFloat(), i = 1 .. tries)]);
for i to tries do
if x[i]^2+y[i]^2 < 1 then s := s+1 end if;
end do:
evalf(4*s/tries)
Then the answer is correct. I have no idea why i can't generate number in "for" loop.
I've founded that the mean of it is the same, but the variance is different.
For:
tries := 100000;
A := Array([seq(GenerateFloat(), i = 1 .. 2*tries)]);
s1 := Array([seq(A[i]^2+A[tries+i]^2, i = 1 .. tries)]);
Mean(s1);
Variance(s1);
s2 := Array([seq(GenerateFloat()^2+GenerateFloat()^2, i = 1 .. tries)]);
Mean(s2);
Variance(s2);
output is:
0.6702112097021581
0.17845439723457215
0.664707674135025
0.35463131700965245
What's wrong with it? GenerateFloat() should be as uniform as possible.
Automatic simplification is turning your,
GenerateFloat()^2+GenerateFloat()^2
into,
2*GenerateFloat()^2
before GenerateFloat() is evaluated.
One simple change to get it to work as you expected would be separate them. Eg,
restart:
with(RandomTools[MersenneTwister]):
tries := 10^4:
s := 0:
for i to tries do
t1,t2 := GenerateFloat(),GenerateFloat();
if t1^2+t2^2 < 1 then s := s+1 end if;
end do:
evalf(4*s/tries);
Another way is to use a slightly different construction which doesn't automatically simplify. Consider, single right quotes (uneval quotes) don't stop automatic simplification (which is a definition of the term if you want).
'f()^2 + f()^2';
2
2 f()
But the following does not automatically simplify,
a:=1:
'f()^2 + a*f()^2';
2 2
f() + a f()
Therefore another easy workaround is,
restart:
with(RandomTools[MersenneTwister]):
tries := 10^4:
s := 0:
a := 1;
for i to tries do
if GenerateFloat()^2 + a*GenerateFloat()^2 < 1 then s := s+1 end if;
end do:
evalf(4*s/tries);
I know how to do basic exception handling. So i can raise a message on divide by zero using the 'try except' method.
What i would like to do is, find the variable that causes this error and then change its value on run time.
For Ex:
procedure Calculate();
var
a, b, c : Double;
begin
try
a := 4; //suppose i take this value from user and he enters 4
b := 0; //suppose i take this value from user and he enters 0
c := a/b;
ShowMessage(FloatToStr(c));
except
on E : EZeroDivide do
begin
ShowMessage('Exception message = '+E.Message);
//i am not sure how to identify that its variable 'b' that is causing the error and has to be changed by a default value
get(E....errorVaraiable);
E....errorVaraiable := 0.00001;
c := a/E....errorVariable;
ShowMessage(FloatToStr(c));
end;
end;
Please, can anyone help me with this?
Here's a modified version of your example that does what you want.
procedure Calculate();
var
a, b, c : Double;
begin
a := 4; //suppose i take this value from user and he enters 4
b := 0; //suppose i take this value from user and he enters 0
if IsZero(b) then
begin
ShowMessage('b cannot be 0')
end
else
begin
c := a/b;
ShowMessage(FloatToStr(c));
end;
end;
I'm new to Matlab and now learning the basic grammar.
I've written the file GetBin.m:
function res = GetBin(num_bin, bin, val)
if val >= bin(num_bin - 1)
res = num_bin;
else
for i = (num_bin - 1) : 1
if val < bin(i)
res = i;
end
end
end
and I call it with:
num_bin = 5;
bin = [48.4,96.8,145.2,193.6]; % bin stands for the intermediate borders, so there are 5 bins
fea_val = GetBin(num_bin,bin,fea(1,1)) % fea is a pre-defined 280x4096 matrix
It returns error:
Error in GetBin (line 2)
if val >= bin(num_bin - 1)
Output argument "res" (and maybe others) not assigned during call to
"/Users/mac/Documents/MATLAB/GetBin.m>GetBin".
Could anybody tell me what's wrong here? Thanks.
You need to ensure that every possible path through your code assigns a value to res.
In your case, it looks like that's not the case, because you have a loop:
for i = (num_bins-1) : 1
...
end
That loop will never iterate (so it will never assign a value to res). You need to explicitly specify that it's a decrementing loop:
for i = (num_bins-1) : -1 : 1
...
end
For more info, see the documentation on the colon operator.
for i = (num_bin - 1) : -1 : 1