tenzr::TorusCostModel¶

Analytic cost model comparing torus and ring all-reduce times.

#include <torus_model.h>

Public Functions¶

Public Functions Documentation¶

function TorusCostModel¶

TorusCostModel(
    TorusDimensions dims,
    NetworkParameters params
)

Parameters:

• dims Torus dimensions.
• params Latency and bandwidth parameters.

Create a cost model for the given torus and network parameters.

function Dimensions¶

inline const TorusDimensions & Dimensions() const

The modelled torus dimensions.

function Parameters¶

inline const NetworkParameters & Parameters() const

The modelled network parameters.

function PredictTimeSeconds¶

double PredictTimeSeconds(
    uint64_t payload_bytes
) const

Parameters:

• payload_bytes Payload size in bytes.
• payload_bytes Number of bytes reduced.

Return:

• Predicted time in seconds.
• Predicted time in seconds.

Predict torus all-reduce time for a payload. Predict all-reduce time over the 3D torus using the Section 5 cost model.

function PredictRingTimeSeconds¶

double PredictRingTimeSeconds(
    uint64_t payload_bytes,
    double ring_bandwidth =0.0
) const

Parameters:

• payload_bytes Payload size in bytes.
• ring_bandwidth Ring bandwidth in bytes/sec, or single-link when <= 0.
• payload_bytes Number of bytes reduced.
• ring_bandwidth Ring bandwidth in bytes/second; derived from the model when non-positive.

Return:

• Predicted time in seconds.
• Predicted time in seconds.

Predict ring all-reduce time for a payload. Predict all-reduce time over a single ring of the same node count.

function SpeedupOverRing¶

double SpeedupOverRing(
    uint64_t payload_bytes,
    double ring_bandwidth =0.0
) const

Parameters:

• payload_bytes Payload size in bytes.
• ring_bandwidth Ring bandwidth in bytes/sec, or single-link when <= 0.
• payload_bytes Number of bytes reduced.
• ring_bandwidth Optional ring bandwidth; defaults to the model's.

Return:

• Speedup factor.
• Speedup factor of torus over ring.

Predicted speedup of the torus over a ring for a payload. Ratio of ring all-reduce time to torus all-reduce time.

function GenerateReport¶

std::string GenerateReport(
    uint64_t payload_bytes
) const

Parameters:

• payload_bytes Payload size in bytes.
• payload_bytes Payload size to model.

Return:

• Formatted report text.
• Multi-line report text.

Render a full comparison report for a payload. Build a formatted torus-vs-ring cost analysis report.

function OptimizeDimensions¶

static TorusDimensions OptimizeDimensions(
    int64_t total_nodes
)

Parameters:

• total_nodes Total node count to factor.
• total_nodes Number of nodes to factor into three dimensions.

Return:

• Chosen torus dimensions.
• Best kx x ky x kz factorization found.

Find the factorisation minimising latency for a node count. Choose the torus factorization of total_nodes that minimizes total hops.