Update Tips and Tricks on structs initialization. #3626

lastperson · 2018-03-01T11:58:29Z

It turns out that in such case:

contract Combine {
    struct Tight {
        bool a;
        bool b;
    }
    Tight t;
    function setTight() public {
        t = Tight(true, true);
    }
    function setTightOptimized() public {
        t.a = true;
        t.b = true;
    }
}

setTight() will consume ~25000 gas, while setTightOptimized() will consume ~20000 gas. It is just the way optimizer works right now.

chriseth · 2018-03-01T13:14:14Z

docs/miscellaneous.rst

+* Initialize storage structs with a single assignment: ``x = MyStruct({a: 1, b: 2});``
+
+.. note::
+    If the storage struct has tightly packed properties, initialize it with separate assignments: ``x.a = 1; x.b = 2;``. In this way it will be easier for optimizer to update storage in one go, thus making assignment cheaper.


Small typo: easier for the optimizer to update

axic · 2018-03-02T16:20:34Z

docs/miscellaneous.rst

+* Initialize storage structs with a single assignment: ``x = MyStruct({a: 1, b: 2});``
+
+.. note::
+    If the storage struct has tightly packed properties, initialize it with separate assignments: ``x.a = 1; x.b = 2;``. In this way it will be easier for the optimizer to update storage in one go, thus making assignment cheaper.


Update Tips and Tricks on structs initialization.

65bd0ff

chriseth suggested changes Mar 1, 2018

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Fix typo.

6546839

chriseth approved these changes Mar 1, 2018

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chriseth merged commit a0d0060 into ethereum:develop Mar 1, 2018

axic reviewed Mar 2, 2018

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Update Tips and Tricks on structs initialization. #3626

Update Tips and Tricks on structs initialization. #3626

lastperson commented Mar 1, 2018

chriseth Mar 1, 2018

axic Mar 2, 2018

Update Tips and Tricks on structs initialization. #3626

Update Tips and Tricks on structs initialization. #3626

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lastperson commented Mar 1, 2018

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