Smart Order Router, or SOR, is an off-chain linear optimization of routing orders across pools for best price execution.

SOR exists in the Bronze release as a way to aggregate liquidity across all Balancer pools. Future releases of Balancer will accomplish this on-chain and allow aggregate contract fillable liquidity.

Liquidity aggregators are free to use the SOR npm package or create their own order routing across pools.

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Overview Of Use And Example

There are two types of swap available:

swapExactIn - i.e. You want to swap exactly 1 ETH as input and SOR will calculate X amount of BAL you receive in return.
or
swapExactOut - i.e. You want to receive exactly 1 BAL and SOR will calculate X amount of ETH you must input.

The SOR will return totalReturn/totalInput as well as a list swaps to achieve the total. The swaps can be executed directly on-chain or with something like the [ExchangeProxy](ADD LINK).

Example Output:

// Following is output for 1BAL->ANT swapExactIn
[
    swaps,
    totalReturnWei,
] = sor.smartOrderRouterMultiHopEpsOfInterest(....

console.log(totalReturnWei);
// 4637139997385211870  - This is the total amount of ANT received for 1BAL

console.log(swaps);

  /*
    This demonstrates a multihop swap going:
    BAL -> REN via pool 0x89ede...
    Then REN -> ANT via pool 0x9e04b42...
  */
  [
    // Multihop swap
    [
      // First sequence in swap
      {
        pool: '0x89edee8eb84a17396d374f7bbc8dc8ed95a133f9',
        tokenIn: '0xba100000625a3754423978a60c9317c58a424e3d',
        tokenOut: '0x408e41876cccdc0f92210600ef50372656052a38',
        swapAmount: '1000000000000000000',
        limitReturnAmount: '0',
        maxPrice: '115792089237316195423570985008687907853269984665640564039457584007913129639935'
      },
      // Second sequence in swap
      {
        pool: '0x9e04b421149043c04b33865d5ecd8f6c87f174b6',
        tokenIn: '0x408e41876cccdc0f92210600ef50372656052a38',
        tokenOut: '0x960b236a07cf122663c4303350609a66a7b288c0',
        swapAmount: '61607795579834805630',
        limitReturnAmount: '0',
        maxPrice: '115792089237316195423570985008687907853269984665640564039457584007913129639935'
      }
    ]
  ]

The file: example-swapExactIn.ts, shows a full example with comments for a USDC->DAI swapExactIn for 1 USDC input:

To Run:

Create a .env file in root dir with your infura provider key: INFURA=your_key

Install dependencies: $ yarn install

Run example: $ ts-node ./test/testScripts/example-swapExactIn.ts