wayang-commons/wayang-core/src/main/java/org/apache/wayang/core/optimizer/costs/DefaultLoadEstimator.java [123:143]:
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                                Arrays.stream(inputCards),
                                Arrays.stream(outputCards)
                        ).sum()
        );
    }

    @Override
    public LoadEstimate calculate(EstimationContext context) {
        final CardinalityEstimate[] inputEstimates = context.getInputCardinalities();
        final CardinalityEstimate[] outputEstimates = context.getOutputCardinalities();
        Validate.isTrue(inputEstimates.length >= this.numInputs || this.numInputs == UNSPECIFIED_NUM_SLOTS,
                "Received %d input estimates, require %d.", inputEstimates.length, this.numInputs);
        Validate.isTrue(outputEstimates.length == this.numOutputs || this.numOutputs == UNSPECIFIED_NUM_SLOTS,
                "Received %d output estimates, require %d.", outputEstimates.length, this.numOutputs);

        long[][] inputEstimateCombinations = this.enumerateCombinations(inputEstimates);
        long[][] outputEstimateCombinations = this.enumerateCombinations(outputEstimates);

        long lowerEstimate = -1, upperEstimate = -1;
        for (int inputEstimateId = 0; inputEstimateId < inputEstimateCombinations.length; inputEstimateId++) {
            for (int outputEstimateId = 0; outputEstimateId < outputEstimateCombinations.length; outputEstimateId++) {
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wayang-commons/wayang-core/src/main/java/org/apache/wayang/core/optimizer/costs/IntervalLoadEstimator.java [99:119]:
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                                Arrays.stream(inputCards),
                                Arrays.stream(outputCards)
                        ).sum()
        );
    }

    @Override
    public LoadEstimate calculate(EstimationContext context) {
        final CardinalityEstimate[] inputEstimates = context.getInputCardinalities();
        final CardinalityEstimate[] outputEstimates = context.getOutputCardinalities();
        Validate.isTrue(inputEstimates.length >= this.numInputs || this.numInputs == UNSPECIFIED_NUM_SLOTS,
                "Received %d input estimates, require %d.", inputEstimates.length, this.numInputs);
        Validate.isTrue(outputEstimates.length == this.numOutputs || this.numOutputs == UNSPECIFIED_NUM_SLOTS,
                "Received %d output estimates, require %d.", outputEstimates.length, this.numOutputs);

        long[][] inputEstimateCombinations = this.enumerateCombinations(inputEstimates);
        long[][] outputEstimateCombinations = this.enumerateCombinations(outputEstimates);

        long lowerEstimate = -1, upperEstimate = -1;
        for (int inputEstimateId = 0; inputEstimateId < inputEstimateCombinations.length; inputEstimateId++) {
            for (int outputEstimateId = 0; outputEstimateId < outputEstimateCombinations.length; outputEstimateId++) {
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