max(): not defined for MX?

[Dave Goel]

max(): not defined for MX?

I notice that max() now works for within matrices, and gets the maximum value within a matrix (right?). However, it seems that it only works for SX, not for MX. Is this a bug or intentional? Is it easy to fix?  I can only use MX in my code because SX would take many days to define, and would run out of memory.

x = MX('x', 2,1);

y = x.max;

f = Function('f', {x}, {y});

f([1;2])

error: casadiMEX: .../casadi/core/mx_node.cpp:291: 'eval' not defined for class N6casadi4MMaxE

error: called from

    call at line 735 column 28

    paren at line 1435 column 13

    subsref at line 1416 column 29

casadi: 3.4.0_for_octave_4.2.1

[Joris Gillis]

Intentional only in the sense that there were higher priorities to focus on,
easy to fix.
https://github.com/casadi/casadi/issues/2043

Best,
  Joris

[Dave Goel]

Hi Joris,

Ah, thanks for that. 

So, it seems that the mmax node did get added for MX, per #2043. But, when you f() on it later, you end up with the "eval not defined" thing. 

The same works on SX, though.

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[Joris Gillis]

Are you using source builds? I can quickly include the functionality which you want (anything else besides evaluation?)

Best,
  Joris

[Dave Goel]

I would love to include source builds, but last time I tried, I was stuck in some kind of dependency hell.

Should I try compiling again?

Just the eval. And, thanks so much!

Dave

 

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[Dave Goel]

Joris,

Many thanks for allowing function definitions for max over MX.

You did ask if I needed anything else beside eval. I apologize for not being clear. I am now stuck at the gradient step, as below. Is it possible to allow gradients as well?

Octave__18:13:59_0005833_7> x=MX.sym('x',1,2);

Octave__18:14:01_0005833_8> y = max(x)*x(1)

y =

(max(x)*x[0])

Octave__18:14:03_0005833_9> z = y.gradient(x)

error: casadiMEX: Error in MX::gradient at .../casadi/core/generic_matrix.hpp:1192:

Error in MX::jtimes at .../casadi/core/generic_matrix.hpp:1181:

Error in MX::reverse at .../casadi/core/mx.cpp:1676:

Error in MXFunction::ad_reverse at .../casadi/core/mx_function.cpp:997:

Error in MX::ad_reverse for node of type N6casadi4MMaxE at .../casadi/core/mx.cpp:1860:

.../casadi/core/mx_node.cpp:311: 'ad_reverse' not defined for class N6casadi4MMaxE

error: called from

    gradient at line 608 column 27

    subsref at line 18 column 30

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[Dave Goel]

For comparison, this works for SX (but SX is unusable for my huge variables). If the same could work for MX, I could actually use max() - 

Octave__18:14:04_0005833_9> x=SX.sym('x', 1,2)

x =

[[x_0, x_1]]

Octave__18:17:13_0005833_10> y = max(x)*x(1)

y =

(fmax(fmax(-inf,x_0),x_1)*x_0)

Octave__18:17:23_0005833_11> z = y.gradient(x)

z =

@1=-inf, @2=fmax(@1,x_0), @3=(x_1<=@2), [[(fmax(@2,x_1)+((!(x_0<=@1))*(@3*x_0))), ((!@3)*x_0)]]

Octave__18:17:29_0005833_12> x=SX.sym('x', 1,2)

x =

[[x_0, x_1]]

Octave__18:17:31_0005833_13> y = max(x)*x(1)

y =

(fmax(fmax(-inf,x_0),x_1)*x_0)

Octave__18:17:32_0005833_14> z = y.gradient(x)

z =

@1=-inf, @2=fmax(@1,x_0), @3=(x_1<=@2), [[(fmax(@2,x_1)+((!(x_0<=@1))*(@3*x_0))), ((!@3)*x_0)]]

Octave__18:17:35_0005833_15> f = Function('f',{x},{z})

f =

f:(i0[1x2])->(o0[1x2]) SXFunction

Octave__18:17:44_0005833_16> f([1 3])

ans =

[[3, 1]]

Octave__18:17:49_0005833_17> f([3 1])

ans =

[[6, 0]]